Dan Margulis Applied Color Theory
16-Bit in LAB
Date: Tue, 09 Nov 2004 20:49:40 -0000
From: “pt210w”
Subject: 16 Bit images only into LAB color space
I attended a seminar at Graph Expo last month where we
were told only 16 Bit images should ever be brought into the LAB
color space for manipulation.
The presenter did not seem to have much information to
support the statement, but no one in the audience seemed to disagree
either.
Does anyone out there know what the peril could be to
working on 8 Bit images in the LAB color space?
Thanks in advance,
Pat Theobald
___________________________________________________________________________
Date: Tue, 09 Nov 2004 16:48:12 -0500
From: Jim Rich
Subject: Re: 16 Bit images only into LAB color space
On 11/9/04 3:49 PM, “pt210w” wrote:
I attended a seminar at Graph Expo last month
where we were
told only 16 Bit images should ever be brought
into the LAB color
space for manipulation.
The presenter did not seem to have much
information to support
the statement, but no one in the audience seemed
to disagree
either. Does anyone out there know what the
peril could be to working
on 8 Bit images in the LAB color space?
This is a controversial topic and some folks get all
wrapped around it.
So my .02 says this:
If you ask folks who are pro 16 bit and who possibly
have religion then you might hear you are doomed to work any other way.
The peril is supposed to be that you get
obvious banding due to image editing and then when you print you might see
it if you don1t use 16 bits. Oh yea and your histograms will have
gaps. But then again, we don't sell those histograms.
And people on the other side of the argument the 8 bit
lovers might say it doesnt matter.
The hard evidence (prints viewed by experts) I have
gathered as well as others on this list like Dan, indicates that
there is no discernable difference between 8 and 16 bit images that have
made the trip to LAB, heavily edited and then printed.
However, IMHO there is not reason to fight over this,
because of how Photoshop works today, I don't see a problem working
in either 8 or 16 bits modes in RGB or LAB or even cmyk.
Jim Rich
___________________________________________________________________________
Date: Tue, 09 Nov 2004 14:14:22 -0700
From: Andrew Rodney
Subject: Re: 16 Bit images only into LAB color space
Here1s the deal. The wider the gamut of a color space,
the more steps between what is only being defined by 256 total steps. So
editing can cause banding and excessive data loss due to view bits
describing more data. You also have to get into LAB from something (RGB
usually) and while Photoshop does this with 20 bit precision, every time
you convert from a smaller to a wider gamut space in 8 bit, especially with
a color space gamut mismatch, you lose even more data. For example, if the
working space is Adobe RGB, which has 256 values available, converting to
8-bit Lab reduces these down to 234 values producing a loss of 22 levels.
Doing the same conversions from ProPhoto RGB reduces the values to only 225
producing a loss of 31 levels. Bruce Lindbloom a well respected color geek
and scientist has a very useful 3Levels Calculator2 that allows one to
enter values to determine the actual number of levels lost to quantization
(see the 3Calc page2 at http://www.brucelindbloom.com ).
Andrew Rodney
http://digitaldog.net/
___________________________________________________________________________
Date: Tue, 09 Nov 2004 22:51:20 -0000
From: “Jen & Ron”
Subject: Re: 16 Bit images only into LAB color space
While CMYK and RGB may be related, Lab does not work
the same when working in curves in Photoshop. Therefore, the peril could be
that Lab is such a potentially powerful tool for color manipulation that
one could easily overdo things causing major problems. It is true while
doing moves in RGB/CMYK may still cause major problems if things are
overdone, it seems it’s allot easier to screw things up while in Lab.
One needs to look at their own situation, for myself - everything that
comes to me is 8bit, so 8bit is my world. Perhaps that is why no one
in the Expo group seemed to disagree. I would also add that doing some
manipulation in Lab is very beneficial to the images I work on, however I
have to admit I probably only take my images into Lab on rare occasions and
that is usually to perform some blending function with my original RGB/CMYK
image to make adjustments to a particular color channel. I would hate to
take a hacksaw to some of Dan Margulis’s chapters in his book just
because someone told me that 16 Bit images should ever be brought into the
Lab color space for manipulation. Especially if they can’t support it
very well.
Ron Scratch
RR Donnelley
___________________________________________________________________________
Date: Wed, 10 Nov 2004 03:29:26 -0000
From: “kuhammer2004”
Subject: Re: 16 Bit images only into LAB color space
A image-editor has to know his limitations (his skill
when using it) when it involves lab. While their is “color
theory” (mathematically)
from a scientific stand point. Their is also
“applied color theory” (hands-on)from the application level.
Sometimes one contradictes the other. Which one contradictes the
other?.........Trial and error.
John Opitz
___________________________________________________________________________
Date: Thu, 11 Nov 2004 07:56:41 EST
From: Dan Margulis
Subject: Re: 16 Bit images only into LAB color space
Pat Theobald writes,
I attended a seminar at Graph Expo last month where we
were told only 16
Bit images should ever be brought into the LAB color
space for manipulation. The
presenter did not seem to have much information to
support the statement, but
no one in the audience seemed to disagree either.
Par for the course. Someone should have asked the
speaker to demonstrate on a real image what the terrible consequences of
working in 8-bit would be, either in LAB or elsewhere. It would then have
been discovered that the speaker had no such image available. Research the
issue, and you’ll find a lot of “experts” saying that
correcting in 16-bit is absolutely critical, creates a night and day
difference, that anyone who doesn’t do it is an amateur, etc., etc.,
etc. What you won’t find are any side-by-side examples of how working
in 16-bit creates a better result at all—let alone a huge increase in
quality—as opposed to doing exactly the same thing in 8-bit.
Most of the 16-bit discussion pertains to working in
CMYK or RGB, but the proponents, none of whom actually work in LAB or
understand very much about mathematics, argue that there are mathematical
reasons why working in LAB is worse in 8-bit. In fact, it’s the
opposite—it’s technically (although as a practical matter,
inconsequential) more damaging to work in 8-bit RGB than 8-bit LAB.
Does anyone out there know what the peril could be to
working on 8 Bit
images in the LAB color space?
Thousands of people use LAB successfully every day,
including hundreds of my own students who report back to me with complaints
and problems as they arise. If anybody was actually encountering this
problem, we’d all know about it.
Dan Margulis
___________________________________________________________________________
Date: Thu, 11 Nov 2004 07:33:29 -0700
From: Andrew Rodney
Subject: Re: 16 Bit images only into LAB color space
on 11/11/04 5:56 AM, Dan Margulis wrote:
Research the issue, and you’ll find a lot of
“experts” saying that correcting in 16-bit
is absolutely critical, creates a
night and day difference, that anyone who
doesn’t do it is an amateur, etc., etc.,
etc.
http:
//www.brucelindbloom.com/index.html?DanMargulis.html
Also be sure to check out Bruce1s background. And no
I1ve not seen any text that says 316-bit is absolutely critical, creates a
night and day difference, that anyone who doesn’t do it is an
amateur, etc., etc2. It1s simply a reflection of math and physics.
Andrew Rodney
http://digitaldog.net/
___________________________________________________________________________
Date: Thu, 11 Nov 2004 11:09:26 -0500
From: Ric Cohn
Subject: Re: 16 Bit images only into LAB color space
On Nov 11, 2004, at 9:33 AM, Andrew Rodney wrote:
And no I’ve not seen any text
that says “16-bit is absolutely critical,
creates a night
and day difference, that anyone who doesn’t do
it is an amateur, etc.,
etc”.
Gee, I sure have. Jeff Schewe was saying exactly this
a few years ago. I don’t know his current views. I assume he’s
backed away from this somewhat as I don’t think he’s at all
stupid. However, I continue to see this claimed every day.
Personally, I still think 16 bit editing has a place,
but I think there are about a hundred other editing issues that will lead
to more visibly higher quality. For the vast majority of images I
don’t believe there will ever (with today’s or tomorrow’s
reproduction methods) be a viewable improvement from working in 16 bit, yet
I see very few images that IMO couldn’t be improved from where they
end up. In my experience the big difference between capture devices (scan
or digital) is the quality of the bits. A device that outputs bad data will
look just as bad in 16 bits as in 8 bits. This is a separate issue from
whether a device needs to be able to use more than 8 bits. Any decent
camera or scanner I’m aware of already uses 12 to 16 bits under the
hood. I would agree that if we are taking the Raw data and the Raw data
needs a large correction (which it generally does) that working in 16 bits
will be necessary.
Just my 2¢.
Ric Cohn
www.riccohn.com
___________________________________________________________________________
Date: Thu, 11 Nov 2004 11:47:12 -0500
From: Bill Morse
Subject: Re: 16 Bit images only into LAB color space
Ouch!! ;^)
Thanks for this reference, Andrew. I would love
to see Dan’s response.
Regards,
Bill Morse
Digital Eye Editions
343 Medford St., Studio 2A
Somerville, MA 02145
(617) 429-3298
PS- from a “16-bit Advocate”, but
hopefully not a closed-minded one.
___________________________________________________________________________
Date: Thu, 11 Nov 2004 09:37:29 -0700
From: Andrew Rodney
Subject: Re: 16 Bit images only into LAB color space
on 11/11/04 9:09 AM, Ric Cohn wrote:
Gee, I sure have. Jeff Schewe was saying exactly this
a few years ago.
I don’t know his current views. I assume
he’s backed away from this
somewhat as I don’t think he’s at all
stupid. However, I continue to
see this claimed every day.
I know Jeff still is a big proponent of working in
high bit.
Personally, I still think 16 bit editing has a place,
but I think there
are about a hundred other editing issues that will
lead to more visibly
higher quality.
I agree. But that doesn’t dilute both the math
behind what happens in 8 bit, or the fact that we don’t have a
crystal ball that tells us what could happen in the editing process in the
future to our files. I for one have a RIP that fully supports 16 bit files
for output (ImagePrint) driving my Epson’s. So while I doubt ink on
paper processes will ever require a high bit file, today I have a printer
that clearly takes advantage of this data. And I have no idea how many
printers will come onto the scene in a year, let alone 10 years that will
allow this.
There are users who need to edit a file and output it
once (to say a press). They really don’t need to be all that
concerned with high bit capabilities. There are others producing very
demanding output that do. It’s all about flexibility. To suggest,
based on one kind of output useage that high bit editing is smoke and
mirrors is pretty close minded considering how editing and output devices
have improved since desktop imaging started with Photoshop 1.0.7!
Andrew Rodney
http://digitaldog.net/
___________________________________________________________________________
Date: Thu, 11 Nov 2004 19:14:34 EST
From: Dan Margulis
Subject: Re: 16 Bit images only into LAB color space
Andrew Rodney writes,
And no I1ve not seen any text that says 316-bit is
absolutely critical,
creates a night and day difference, that anyone who
doesn’t do it is an amateur, etc., etc2.
As is so often the case when one of Andrew’s pet
color concepts goes down the tubes, his memory becomes unreliable.
In the current edition of my book, I quote at some
length a 2001 thread in AdobeForums where a number of “experts”
were on the defensive, because several participants were asking them why,
if 16-bit corrections were so dramatically better, they couldn’t
supply any images that showed this. The experts said they were too busy to
do so, but that we should take their word for it, and tried to change the
subject into a discussion of whether I was a wicked and evil person.
Apparently feeling that if they only sounded decisive enough the skeptics
might go away, they said the following things, all direct quotes, separated
by ellipses, many different speakers, I forget which one is Andrew.
"16 bit capability is critical during all aspects
of tone compression....The difference CAN be seen in the final output very
easily. Most definitely on the printed page, especially when using
high-quality halftoning and even more so to a film recorder....It’s
very easy to see that substantial color & tone editing will eventually
result in data loss and banding....If it means the difference between
taking a 16-bit image capture and editing that to the final image and
taking that same image in only 8-bit and editing that to the final image
then there is a difference like between the day and the night...Yes, if a
histogram full of holes has no impact on final output, then throw away the
graphs and just get on with the print run. However, all of us have Real
World Output showing the superiority of superior data acquisition....My
advice? Take the information you’ve read here to the bank. Stop
doubting and start applying what you’ve learned here....If you really
start out with a RAW image in high-bit form and a raw image downsampled to
8 bits, the difference really is night and day....It’s totally
obvious to anyone who looks that it’s very advantageous to do the big
moves on high-bit data."
The following year there was considerable discussion
here, in which Andrew participated vociferously, of the merits of the
following statement by one of the above experts, who presented it in
writing to a class at a major trade show:
"I’m not sure just how to stress the
importance of doing color and tone corrections in 16 bits in Photoshop. One
can point to the obvious advantages...I suppose the difference could be
characterized as professional vs. recreational use of Photoshop"
That thread can be found at
http:
//www.ledet.com/margulis/ACT_postings/ColorCorrection/ACT-16-bit-2002.htm
Now, certainly, none of these experts would be likely
to say any such thing today (although, AFAIK, none of them have just bitten
the bullet and said that they were wrong, as I hope the rest of us would if
we were in their shoes). It is, however, always useful to look back on what
they *did* say at the time, lest revisionist historians suggest that they
didn’t.
Dan Margulis
___________________________________________________________________________
Date: Thu, 11 Nov 2004 23:02:01 -0600
From: “john opitz”
Subject: Re:16 Bit images only into LAB color space
From: Bill Morse
Ouch!! ;^)
Thanks for this reference, Andrew. I would love
to see Dan’s response.
This is an old reference. This is not anything new.
Not speaking for The Man, but if you have The Book..... in Chapter 15,
starting on page 310 he explains the 8 bit vs. 16 bit. The images and the
curves The Man applied are on the cd. Also you can find it here...
http:
//www.ledet.com/margulis/PP7_Ch15_Resolution.pdf
Refer to page 16 of this pdf.
John Opitz
___________________________________________________________________________
Date: Thu, 11 Nov 2004 23:17:43 EST
From: Dan Margulis
Subject: Re: 16 Bit images only into LAB color space
Bill Morse writes,
Thanks for this reference, Andrew. I would love
to see Dan’s response.
I find the whole topic so distasteful that I
ordinarily pay no attention when it arises, but since it has come up I will
make one post, but no more.
I have no objection to people who disagree with my
opinions, even when they aren’t particularly civil about it;
that’s how things get sorted out eventually.
The site in question is a different animal. It
involves a frustrated individual deliberately posting information that he
knows to be false. Plus, Andrew Rodney, who knows full well that the page
is a troll, repeatedly posts links to it.
Bruce Lindbloom’s whole contention is that
before I tested the 16-bit images, I converted them to 8-bit and then
reconverted them to 16-bit before applying curves. If that were true, it
would be like a test comparing how well two washing machines work on the
same kind of load, except that one of them had a bucket of mud poured in it
first.
Of course, it’s ridiculous. What he is seizing
on and deliberately misinterpreting is a phrase in my original description
of how I would proceed. I said I would run a series of drastic corrections
on two copies of each of many, many files. One set of corrections would be
done entirely in 16-bit and the conversion to 8-bit would come only at the
end; then, on a copy of the file, I would convert to 8-bit immediately and
load the identical actions, whereupon I would compare the two.
Makes sense so far, but I added: if it turns out that
the version done in 16-bit is significantly better, then, and only then,
I’d run a third test—converting the 8-bit file back to 16-bit
before correcting it, to see if there wasn’t something about the
calculation method that was producing the better result, rather than just
the extra data.
I’ve studied what happens when you do that, and
it’s pretty interesting. However, it never was any part of my testing
of the images, for the simple reason that the corrections done in 16-bit
all the way were never any better than in 8-bit, regardless of how drastic
they were.
Bruce asked a lot of questions about this at the time,
including correspondence with me off-list. I was aware then that he was
trolling, because he was professing to be neutral on the subject, whereas
on the ColorSync list he had recently called 16-bit correction “a
must” in certain circumstances. So, when I saw he was trying to poke
a hole in the methodology, I made sure that he grasped completely what the
purpose of the hypothetical 16>8>16 conversion was.
There is no possibility that he misunderstood this;
indeed, he could not possibly be so stupid as to think that anyone would
perform a test this way. Nevertheless, he chose to post what he did,
knowing that it was false.
While the content of the page collapses when this is
understood, there is one other side note. Bruce accuses me of keeping the
results to myself and appointing myself the sole judge, which he knows
perfectly well is not true. I printed 10 pages of side-by-side samples in
my current book, many at extreme magnifications. The versions are not
identified until a box later in the chapter, and readers are invited to
judge for themselves which is which, plus, I indicate how I voted when I
first saw the proofs and did not know which was which. The original 16-bit
files, and the corrections I applied to them, are all on the book’s
CD and anybody who likes can either verify what I did or do their own
experiments.
What prompted the accusation was an unfortunate
incident involving my first round of tests. The test files were provided by
a list member whom I did not know at the time. After I performed the tests,
I was flabbergasted to learn that he would not give me permission to
exhibit the images and results publicly, which I thought was the whole
point of the exercise. He did confirm, several times, on this list and at
least two others, that he and I were not personally acquainted; that he
believed I did not realize he was not giving permission; and that he had
seen my results and that I was describing them accurately. When Bruce
challenged him, he offered to give him pieces of the pictures (and my
results) that would have been sufficient for Bruce to verify the findings,
but Bruce refused to take them.
Because of this incident, I changed the rules. I said
I would not do any testing on 16-bit files without an advance agreement
enabling me to publish them and to release the raw data to illustrate
whatever was found. Ric Cohn and a couple of other people kindly agreed to
allow their images to be used in this fashion. Consequently the files are
available for anybody on the CD.
The upshot of this: you guessed it. With the rules now
having been altered to accommodate Bruce, Bruce wrote that the test was
invalid, because the rules had been changed.
In summary: the issue with the page is not its
dishonesty as much as its irrelevance. Bruce is the one advocating the
inconvenient workflow, just as it would be if he said that there’s a
big quality difference if one only wears garlic around the neck while
booting Photoshop up. Nobody can disprove that, because if your tests show
that there’s no difference, probably the garlic was too old or there
wasn’t enough of it.
Similarly, nobody can disprove that 16-bit correction
may be better under some circumstances, because nobody can test every
conceivable image with every conceivable tool. However, the only two people
who have ever run extensive tests—Jim Rich and I—tortured the
images almost beyond belief and still were not able to identify any areas
in which 16-bit correction did better with a color photograph.
It’s painfully apparent at this point that Bruce
and the others have never actually done side-by-side tests to support their
theories. Otherwise, we’d have seen examples long ago. For anybody
wishing to successfully advocate the 16-bit workflow, the recipe is quite
easy:
1) Here is a photographic image;
2) Here is what I did to it in 16-bit;
3) If you convert it to 8-bit first and
then repeat what I did, it looks a lot worse.
Without that demonstration, he has put up a blank
page, IMHO.
Dan Margulis
___________________________________________________________________________
Date: Thu, 11 Nov 2004 23:04:06 -0700
From: Ron Kelly
Subject: Re: 16 Bit images only into LAB color space
I must admit that I haven’t done extensive
personal testing on the question of 8 bit vs.16 bit editing.
Why not? Well, I’m getting along just fine in 8
bit. I have no problems that I know of that 16 bit editing would fix, and I
know of several problems I would have using 16 bit.
What problems are those? Much bigger file sizes,
limited editing tools, more time watching the beach ball revolve, clogged
hard drives and a lot more CDs and DVDs to burn and catalog, to name a few.
What problems would 16 bit editing solve? Well,
I suppose, I wouldn’t get as much banding in a heavily edited
file. But wait, I don’t get banding now, and I routinely do some
pretty serious curving. I can only think of one image where banding was a
problem in output. I must admit that I didn’t think to try 16 bit
editing; I just selected the sky and added a bit of noise.
Maybe I’m missing something, but I don’t
know what I’m supposed to get out of 16 bits except maybe a bit of
status with the color geeks. Anyone? Richer colors? Sharper results? More
shadow detail?
And what if you don’t make heavy edits on a
file? Is there any theoretical advantage to 16 bits here? In other words,
does the average image have anything to gain from 16 bit, or is it just the
very rare ones?
The only examples I’ve seen that purported to
show the benefits of 16 bit editing were terrible photographs to begin
with. The author (Bruce Fraser) was trying to make a silk purse out of a
pig’s ear, and it didn’t work in my opinion. If 16 bit is only
effective on this type of image, then I think I’ll do my best not to
start with a piece of crap to begin with.
My comment relating to this thread is that it seems
like another case of people reacting to what they see in the process, and
not the result of that process. Many others on this list have observed that
we don’t sell histograms to which I concur.
What I have proven to myself in my own personal work
is that I can get excellent results in 8 bits. Certainly, my files are
usually pretty good to start with; for example they’re not scans of
negatives that are two-stops underexposed. Your situation may be different,
I realize. Just don’t expect to start from this position and get a
result that’s as good as could be done properly, using only 8 bits
but with a good original.
Those of you who are using 16 bit editing, have you
proven it to yourself that it’s necessary? Vital? Beneficial?
Noticeable? Detectable? All the time? Sometimes? Ever?
If you have, but you go a long way down that
progression, perhaps you should reconsider your workflow.
And if you’re up at the front of the
progression, congratulations! You’ve just won the 8 vs.16 bit
challenge. Now please post your images for all to see.
Finally, ask yourself this question: is it not true
that if two techniques yield the same result, the better method is the
simpler, faster, the one that is a much lighter weight to bear?
Perhaps some of you are taken in by the old logic that
you used to use in photography: the bigger the camera, the better the
pictures. That doesn’t hold true here; this isn’t 4x5 vs. 35mm;
more bits aren’t necessarily better.
Cheers,
Ron Kelly
___________________________________________________________________________
Date: Fri, 12 Nov 2004 05:00:34 -0800
(PST)
From: Mike Bevans
Subject: Re: 16 Bit images only into LAB color space
I will tell you something
16 bit IS good for... charging customers by
file size. Everyone from color management
consulants, to scanning services, to camera
salesman, to photographers uses this trick.
I agree with Dan, this is a tiresome debate. I
also agree with Ron. I personallly think that only dogs can hear in 16 bit.
On a similar note, I work with the BetterLight camera,
shooting 8 bit files for fine art reproduction. No one
has ever had a problem with 8 bit files. I have encountered printers
who tell me my files are too lo-rez for their printers, since I scan
at 300ppi. The files I am producing are over 4000x5000 pixels.
I know from my own experience that you can print
photographic images banner-sized from these files.
Still, I encounter printers who want to
up-rez the files to match their print dimensions. This
makes for softer images and cumbersome file sizes. Has anyone
else had this problem sending work to print?
-Mike Bevans
___________________________________________________________________________
Date: Fri, 12 Nov 2004 07:06:19 -0700
From: Andrew Rodney
Subject: Re: 16 Bit images only into LAB color space
on 11/11/04 5:14 PM, Dan Margulis wrote:
As is so often the case when one of Andrew’s pet
color concepts goes down the
tubes, his memory becomes unreliable.
Post a quote and a reference please.
Apparently feeling that if they only sounded decisive
enough the skeptics
might go away, they said the following things, all
direct quotes, separated
by ellipses, many different speakers, I forget which
one is Andrew.
If you1re going to put quotes here you better get your
facts straight bud. You may not remember? Then either find the exact post
and a reference or pull my name from this bogus list of quotes. Be accurate
Dan.
I1m still waiting for you to respond to Bruce
Lindblooms page.
Andrew Rodney
http://digitaldog.net/
___________________________________________________________________________
Date: Fri, 12 Nov 2004 07:12:19 -0700
From: Andrew Rodney
Subject: Re: 16 Bit images only into LAB color space
Bill Morse writes,
Thanks for this reference, Andrew. I would love
to see Dan’s response.
Well Dan wrote a lot but didn1t address anything Bruce
challenged him on. Bottom line is on this list, Dan1s right. There1s no
need to argue science. I actually considered cc1ing this to Bruce but in
the end, it1s a waste of bandwidth. Read Bruce1s page, do your own tests.
Consider the math (that1s all computers understand) and consider what will
happen to the file in the future and what devices it might be sent to. Then
consider the downsides of 16-bit editing and do what you feel is right.
Gee, I wonder why the vast majority of input (even
consumer devices) produce more than 8 bit per color????
Andrew Rodney
http://digitaldog.net/
___________________________________________________________________________
Date: Fri, 12 Nov 2004 10:11:33 -0500
From: Fred D Yocum
Subject: Re: 16 Bit images only into LAB color space
The message I received seemed to do a fairly good job
of addressing the issues raised on the Mr. Lindbloom’s page.
Dan Margulis on 11/11/2004 23:17
“I printed 10 pages of side-by-side samples in
my current book, many at extreme
magnifications. The versions are not identified until
a box later in the chapter,
and readers are invited to judge for themselves which
is which, plus, I indicate
how I voted when I first saw the proofs and did not
know which was which. The
original 16-bit files, and the corrections I applied
to them, are all on the
book’s CD and anybody who likes can either
verify what I did or do their own
experiments.”
Computers have is math, humans have more flexible
forms of perception - what we perceive is not necessarily what is there or
not there. That goes for this little verbal fire storm as well as the bit
level of files. If you don’t like Dan’s results, perhaps you
can invent you own tests and publish your own results.
F D Yocum
Graphic Designer
___________________________________________________________________________
Date: Fri, 12 Nov 2004 08:12:21 -0700
From: Andrew Rodney
Subject: 16 Bit images only into LAB color space
Check out:
http:
//www.photoshoptechniques.com/forum/archive/index.php/t-336.html
This appears to be one of the first or original sets
of discussions (including the bit about recreational users). You1ll find no
posts by yours truly. You1ll also find some sensible advise from Bruce
Fraser such as:
"I have never, anywhere, claimed that 16 bits is
superior to 8 bits. What I’ve
said is that from my own experience, 16 bits gives a
great deal more editing
headroom and flexibility than 8 bits. If you
don’t need it, don’t use it. I’ve
always been pretty straightforward about the plusses
and minusses, and I’m not
trying to sell anyone on 16-bit workflows."
Andrew Rodney
http://digitaldog.net/
___________________________________________________________________________
Date: Fri, 12 Nov 2004 17:20:59 +0100
From: Werner Tschan
Subject: Re: 16 Bit images only into LAB color space
Andrew Rodney writes
Gee, I wonder why the vast majority of input (even
consumer devices) produce
more than 8 bit per color????
The dynamics of modern digital cameras is such, that
you have a much wider contrast range than (most — and surely more
than any slide-) film could produce. When I process RAW files into
TIFF files I have the possibility to shift 2,5 Stops each way without
getting into serious problems (Canon EOS1Ds with C1 PRO from Phase One). In
my understanding it’s here where the more than 8 bits of the camera
come into play.
Could this be the answer to your question, or am I
getting things wrong?
Werner Tschan
___________________________________________________________________________
Date: Fri, 12 Nov 2004 09:46:13 -0700
From: Ron Kelly
Subject: Re: 16 Bit images only into LAB color space
Werner:
Try this test:
Lock your camera down on a tripod and photograph some
scene that has a full dynamic range, ie shadows with detail and highlights
with detail, maybe some speculars too.
Bracket your photographs. Choose one that appears to
be the best exposure for the scene, and choose one that is 2.5 stops darker
than that.
Open up the darker one, and manipulate it in software
to match the “best exposure” and compare the results. Use
on-screen and/or prints for your comparison, but be sure to use the
criteria that you most often have for “the final result.”
What does your comparison show? Are the results
identical?
Ron Kelly
___________________________________________________________________________
Date: Fri, 12 Nov 2004 18:49:52 -0700
From: Ron Kelly
Subject: 16 bit color
People:
I was just out jogging and I was mulling over the
whole 16 bit vs. 8 bit thing. As I rounded a curve by the river, I was
thrilled to see a gorgeous sunset.
Naturally, this got me to thinking: what color space
does God use? What bit depth?
After consulting my fellow jogger, who is very
strong in physics, we decided that God uses 64 bits. He said, (sic)
“There is just no way that you need any more than 64 bits to describe
ALL the colours, x-rays, and gluons or whatever. I don’t know exactly
how many wavelengths that is, but it’s A LOT.”
Which begs the obvious question: what if you used 128
bits for edits? I know, I know, there are no devices, software, or monitors
for this (yet!) BUT JUST THINK! Maybe someday you could have better color
than God! (VERY Big ; - ) )
I don’t really want to re-ignite the whole
thing, but I just couldn’t resist.
God Bless all of you who contribute; we may not
all have the same opinion but that doesn’t mean we can try to
understand each other, and have a little bit of fun too.
Sorry for wasting your bandwidth,
Ron Kelly
___________________________________________________________________________
Date: Sat, 13 Nov 2004 07:13:34 -0800
From: Mike Russell
Subject: Re: 16 bit color
Ron Kelly wrote:
Naturally, this got me to thinking: what color space
does God use?
What bit depth?
God uses double precision floating point. At the
end of the day, unlike His creations, God is big on pictures and scant on
words.
BTW, He is not big on upgrades and is still using an
early version of CP/M, running on an overclocked Sol, with hard sectored 8
inch floppies.
Mike Russell
www.curvemeister.com
www.geigy.2y.net
___________________________________________________________________________
Date: Sat, 13 Nov 2004 10:33:44 -0500
From: David Deaubrey Tighe
Subject: Re: 16 bit color
Makes me wonder what color looked like a few billion
years ago.
Was Sol redder or more yellow? Were natural dust and
volcanic dust filters
warmer than our carbon filters? Moreover, what sort of
profile would it take
to match the cones of early hominids?
___________________________________________________________________________
Date: Sat, 13 Nov 2004 11:27:46 -0500
From: Jim Rich
Subject: Re: 16 bit color
Which begs the obvious question: what if you used 128
bits for edits? I
know, I know, there are no devices, software, or
monitors for this
(yet!) BUT JUST THINK! Maybe someday you could have
better color than
God! (VERY Big ; - ) )
Ron,
At first seeing your amusing comments
about God and higher bit depth I wrote what I had hoped to me would be an
entertaining response:
But what if you don1t believe in God. Then are you
stuck with those devilish 8 bits?
Then it became clearer that you are on to
something here that has been alluded to all along. This is a true
religious experience for a lot of folks who are on both sides of the issue.
The 8 v 16 bits argument is now is about his or her belief system and
for those people who know they have religion because they have been
to the mountain, there is a need to stand their ground no matter what the
evidence says. And that this argument is more about peoples core beliefs
(and egos) than it is about technology and facts.
Sounds just like the our last presidential election.
My .02.
Jim Rich
___________________________________________________________________________
Date: Sat, 13 Nov 2004 16:51:32 -0000
From: “Bob Frost”
Subject: Re: 16 bit color
There was none. Color only exists in the mind of an
suitably-equipped observer!
Bob Frost.
From: “David Deaubrey Tighe”
Makes me wonder what color looked like a few billion
years ago.
___________________________________________________________________________
Date: Sat, 13 Nov 2004 08:41:48 -0800
From: Mike Russell
Subject: Evolution and color spaces
David Deaubrey Tighe wrote:
Makes me wonder what color looked like a few billion
years ago.
Was Sol redder or more yellow? Were natural dust and
volcanic dust
filters warmer than our carbon filters? Moreover, what
sort of
profile would it take to match the cones of early
hominids?
There’s no need to guess about this, as this is
dictated by the molecular structure of the light senstitive dyes, and they
have a well-documented time line in our DNA, and that of other species.
Chevreaux documented the adaptive nature of color vision 100 years
ago - we use something more like individual curves, not profiles, for our
vision.
Looking at our retinas under a microscope, cones come
in three colors, cyan, magenta, and yellow. Rods, which are the more
primitive sensor, are senstive to monochrome only, and used for edge
detection at normal light levels. So, it may be argued, with
anatomical support, that we are CMYK creatures, with sharpening in the K
channel, not RGB ones.
There’s nothing magical about three cones.
Multispectral is the order of the day for many animals. Certain
birds, including Mallards have five different light sensitive pigments.
Add the rods, and you have hexachrome or hifi color.
It would not take much, just the presence of a fourth
type of cone, for a person to have multi-spectral vision - and such people
may be walking among us in small numbers. Perhaps a member of this
discussion group could design a billboard that would be readable only by
these people.
Mike Russell
www.curvemeister.com
www.geigy.2y.net
___________________________________________________________________________
Date: Sat, 13 Nov 2004 12:34:35 -0500
From: David Deaubrey Tighe
Subject: Re: Evolution and color spaces
Looking at our retinas under a microscope, cones come
in three colors, cyan,
magenta, and yellow. Rods, which are the more
primitive sensor, are
senstive to monochrome only, and used for edge
detection at normal light
levels. So, it may be argued, with anatomical
support, that we are CMYK
creatures, with sharpening in the K channel, not RGB
ones.
Mike,
Wow, interesting stuff.
Awhile back I was reading something about
color-blindness (specifically what is called red-green color blindness). I
recall the article said it should more accurately be called
“magenta-green” color blindness. This explanation made color
blindness sound like it was occurring in a LAB model.
I don’t know anything about the biology of
color, but it’s fascinating.
David
___________________________________________________________________________
Date: Sat, 13 Nov 2004 18:34:00 -0000
From: “Bob Frost”
Subject: Re: Evolution and color spaces
David,
An excellent book to read is ‘Vision and Art -
The Biology of Seeing’ by Margaret Livingstone (Harvard
neurobiologist).
Bob Frost.
___________________________________________________________________________
Date: Sat, 13 Nov 2004 14:04:53 EST
From: Dan Margulis
Subject: Re: 16 Bit images only into LAB color space
Mike Bevans writes,
I have encountered printers who tell
me my files are too lo-rez for their printers,
since I scan at
300ppi. The files I am producing are over
4000x5000 pixels. I
know from my own experience
that you can print photographic
images banner-sized from these
files. Still, I encounter
printers who want to up-rez
the files to match their print
dimensions. This makes for softer
images and cumbersome file
sizes. Has anyone else had this problem sending work
to print?
Certainly. This goes hand in hand with Terry’s
post yesterday. There are some very knowledgeable printers who hang out on
this list and elsewhere who know most of what there is to know about
prepress. As I remarked yesterday, however, the chances of finding a
printer who knows what his own dot gain is or has any idea of what black
generation to use are not high. Similarly, few printers have any clue as to
what resolution is necessary.
What you get, therefore, is some minimum-wage person
who runs the incoming job through FlightCheck or something similar and
demands that whatever the program thinks it requires be complied with.
Since this is the kind of treatment that *I* often get
from printers (who often get all huffy when I say that the resolution is
sufficient, and tell me I should go off and read a book called
“Professional Photoshop” before having the gall to challenge a
printer on what they do best), I can only imagine what a PITA it is for
other people.
Unfortunately, there’s nothing for it but to
improve one’s own knowledge—if you don’t know more about
image prep than the typical printer does, there’s a problem. In the
this-is-hard-to-believe department, I offer just three examples:
*******************************
1) My publisher calls me up asking how to deal with
another author’s book. The book is about Excel or some other
non-graphics software. There are no color images other than screen grabs,
and there are about 500 of them. It’s on press, but the printer says
it won’t print the book unless each and every one is upsized to 300
ppi. Author refuses. Publisher being berated by printer for providing
inadequate files. It actually takes a call from me explaining what the
purpose of resolution is, and why 300 ppi is three times higher than what
you need for a screen grab, before the printer will relent.
*******************************
2) I get a call in the middle of the night during the
REPRINT of one of my books—that is, after the book has already
printed successfully, using the same exact files. Following dialog ensues:
Printer’s CSR: Sir, I’m sorry to wake you,
but we’ve had to stop the pressrun because there’s a problem
with one of your files. It doesn’t have enough resolution and the
pressman is saying that it looks like [doo-doo] in print.
DM: What picture is it?
CSR: It’s the one on page 147, top left.
DM: I do love my book but not quite enough to have a
bleeping copy of it here with me in bed. What is the picture of, please?
CSR: I don’t know. The pressman didn’t
tell me.
DM: Well, do you have the bleeping dyluxes in front of
you?
CSR: Yes, sir.
DM: What does the caption for that picture read?
CSR (reading): “This image illustrates the
perils of printing with inadequate resolution.”
*******************************
3) The following is unsolicited correspondence:
Subj: Question concerning Levels.
Date: Friday, February 21, 2003 10:48:15 PM
To: dmargulis@aol.com
Hello Dan,
I just purchased your 4th edition of Professional
Photoshop. It is just as friendly and wonderful to read as the first one. I
work in a Screen print shop and rarely get to use a majority of your cool
moves. Earlier today, while studying your book and duplicating your moves,
the Production Manager tried to explain to me why the moves wouldn’t
work for high end printing. His evidence laid in the levels dialog box.
After the moves, the levels would show up spiky and with gaps. He insisted
the image would print like crap. He had me enlarge the image by one pixel
and upon checking the levels, they were now smoother. I looked at him like
he was crazy and muttered that I would look into it. My question to you, is
he crazy or does he have some sort of valid point?
*******************************
You can’t make this stuff up.
Dan Margulis
___________________________________________________________________________
Date: Sat, 13 Nov 2004 19:22:38 -0000
From: “Bob Frost”
Subject: Re: Evolution and color spaces
Mike,
Looking at our retinas under a microscope, cones come
in three colors, cyan,
magenta, and yellow. Rods, which are the more
primitive sensor, are
senstive to monochrome only, and used for edge
detection at normal light
levels. So, it may be argued, with anatomical
support, that we are CMYK
creatures, with sharpening in the K channel, not RGB
ones.
The actual peak response of the three types of cones
in our eyes is in the violet, green and yellow regions, so that perhaps
makes us VGY creatures!. The rods also have peak response in the green
region. Fish apparently do have cones that peak in the red region, but we
don’t.
But it is not so simple since each cone has a very
broad response to light. The longwavelength (or ‘Blue’) cones
peak in the magenta but respond over the range from UV to green. The middle
wavelength (or ‘Green’) cones peak in the green but respond
over the whole visible range of UV to red, as do the shortwavelength (or
‘Red’) cones which peak in the yellow but respond more strongly
in the red than do the middlewavelength cones. This means we can’t
tell anything about the color of the light from the response of a single
cone type. Only by comparing the ratios of the responses of all three cone
types can the brain work out what wavelengths of light have stimulated
them.
It would not take much, just the presence of a fourth
type of cone, for a
person to have multi-spectral vision - and such people
may be walking among
us in small numbers.
In a way, rods are our fourth type of color receptor!
Which is why colors seem different at dusk when the rods come into play and
our cones become less efficient. During the daytime when we are using
mainly our cones for color and luminance detection, if we look at a blue
bowl with red cherries in, it appears that the cherries are brighter than
the bowl. But at dusk as our rods play a greater part in detecting
luminance, the blue bowl becomes brighter than the red cherries, because
the rods are more sensitive to blue light than to red!!
Bob Frost.
___________________________________________________________________________
Date: Sat, 13 Nov 2004 16:18:59 -0500
From: todie
Subject: Re: Evolution and color spaces
On Nov 13, 2004, at 11:41 AM, Mike Russell wrote:
Looking at our retinas under a microscope, cones come
in three colors, cyan,
magenta, and yellow. Rods, which are the more
primitive sensor, are
senstive to monochrome only, and used for edge
detection at normal light
levels. So, it may be argued, with anatomical
support, that we are CMYK
creatures, with sharpening in the K channel, not RGB
ones.
This is fun and instructive, but how come we can see
way outside the current CMYK spaces?
(I’m aware that “current” may be
part of the answer)
Laurentiu Todie
___________________________________________________________________________
Date: Sat, 13 Nov 2004 17:08:05 -0600
From: “Mike Davis”
Subject: RE: Color bit depth
Backing away from the trees here a minute and looking
at things as a relative novice, I seem to recall that the ability of the
human eye and brain to recognize (perceive) adjacent similar color
differences is quite limited. If one uses 8 bit colors and generates
sufficient adjacent color differential as the direct result of an edit,
then there may be a case for the use of 16 bit color. However, at the
pixel level, one cannot discern close adjacent color differences without
extreme magnification and an electronic meter. The eye blends colors
quite well and uses a built in AWB to compensate for what we
“think” the right color is or should be. Even at 72 ppi
on a decent monitor, adjacent pixels are blended, thus leaving the 8 vs. 16
argument moot for the most part.
Having said that, I can also imagine an image with an
incredibly narrow density range being artificially expanded with a curve
(Dan’s fans don’t use levels :-)) which would stretch the gaps
between colors and create a wider range between adjacent pixels (black cat
in a coal bin, polar bear on ice), which in turn would show up in favor of
the 16 bit camp after some extreme editing to prove a point. I
suspect that, mathematically, one could crunch some numbers to make a case
for 16 bit under extreme editing conditions. I also suspect that in
the real world, 8 bit is indistinguishable from 16 bit with
“normal” images. I have tried some tests similar to
Dan’s and have yet to “see” anything that would encourage
me to change to 16 bit files. I’m still testing. In the
real world, I don’t stretch black objects from black thru gray to
white.
Mike Davis
mldavis2 AT sbcglobal DOT net
___________________________________________________________________________
Date: Sat, 13 Nov 2004 23:36:37 EST
From: Dan Margulis
Subject: Re: Evolution and color spaces
David Tighe writes,
Awhile back I was reading something about
color-blindness (specifically what
is called red-green color blindness). I recall the
article said it should
more accurately be called “magenta-green”
color blindness. This explanation
made color blindness sound like it was occurring in a
LAB model.
That would be me. I tested a group of color-blind
people and found that their condition could best be approximated as an
extreme inability to perceive variations in the A channel. The group
appeared to be at least as sensitive as normally-sighted people to changes
in the B channel (further testing needed to say this for sure) but even the
ones with the closest to normal vision could not see a difference in the
image when 50% of the contrast in the A channel was removed. The ones who
were most spectacularly colorblind could not see a difference even when the
A channel was inverted, i.e. magenta objects turning green and vice versa.
Dan Margulis
___________________________________________________________________________
Date: Sun, 14 Nov 2004 00:17:56 -0500
From: David Deaubrey Tighe
Subject: Re: Evolution and color spaces
That would be me. I tested a group of color-blind
people and found that their
condition could best be approximated as an extreme
inability to perceive
variations in the A channel.
Dan,
Yes, now I recall you discussing that. Sorry I
couldn’t give you attribution in my original paraphrase.
Was that in your book or from online? I was going
through some old files this week from CompuServe’s Pre Press Forum
and perhaps you mentioned it there?
My graduate advisor, a painter, is color blind.
I’ve also discussed some of these interpretations with him. FYI, I
used to be a commercial pre press guy, now I am an artist/printmaker and
mixing the old world methods with today’s high tech.
David
___________________________________________________________________________
Date: Sun, 14 Nov 2004 09:23:38 EST
From: Dan Margulis
Subject: Re: Evolution and color spaces
David Tighe writes,
Was that in your book or from online? I was going
through some old files
this week from CompuServe’s Pre Press Forum and
perhaps you mentioned it
there?
It was in a column in Electronic Publishing.
Dan Margulis
___________________________________________________________________________
Date: Sun, 14 Nov 2004 10:03:21 EST
From: Dan Margulis
Subject: Re: Color bit depth
Mike Davis writes,
Having said that, I can also imagine an image with an
incredibly narrow
density range being artificially expanded with a curve
(Dan’s fans don’t
use levels :-)) which would stretch the gaps between
colors and create a
wider range between adjacent pixels (black cat in a
coal bin, polar bear
on ice), which in turn would show up in favor of the
16 bit camp after
some extreme editing to prove a point.
I thought that such a thing would happen myself, which
is why I included exactly such images in my tests. To my surprise, there
was no advantage to editing in 16-bit even in such an extreme case. If
anybody else has tried a side-by-side test on such an image and gotten a
different result, I’d be happy to hear about it.
Dan Margulis
___________________________________________________________________________
Date: Sun, 14 Nov 2004 10:00:52 EST
From: Dan Margulis
Subject: Re: 16 Bit images only into LAB color space
Andrew Rodney writes,
This appears to be one of the first or original sets
of discussions (including
the bit about recreational users). You1ll find no
posts by yours truly.
You1ll also find some sensible advise from Bruce
Fraser such as:
The argument concerns Andrew’s revisionist
claims that he has never heard anyone (like, for example, his own
business partners) say that correction in 16-bit creates a night-and-day
difference, or that anyone who doesn’t work that way is a
recreational as opposed to a professional user. I posted two lengthy
quotes showing that he had in fact heard exactly those things from
his friends. Now, we get the above—a reference to an unrelated
group posted a year after the one I cited, where the poster has already
changed his mind considerably.
Because of the possibility that the group may be
misled by this obvious red herring, I reluctantly post the complete,
unedited text of the 2001 posting by the person Andrew now quotes as
taking a soft line on the issue. A reminder that this individual was only
one of several persons posting substantially similar comments at the
time. And, as Andrew’s later post shows, neither this person nor
anybody else in their right mind would say such a thing today. I trust this
brings this episode to a close.
NOTE: With respect to the first paragraph, the poster
was immediately corrected publcly by the person providing me with many of
the raw scans used in my book. The originals *were* untouched, *were* in
16-bit, and had not been toned in any way, whether by setting white and
black point or any other modification. Some of the tested moves were almost
inconceivably extreme, far more than would be encountered in any plausible
real-life scenario. Therefore, they are precisely the kind of files that
the speaker then thought would be so much better in 16-bit that “the
difference really is night and day” and “it’s totally
obvious to anyone who looks.” As those who have read my book know, it
is in fact extremely difficult to tell the two sets of images apart, even
at high magnifications.
My apologies to the group for the waste of bandwidth.
Dan Margulis
*********************************
Bruce Fraser - 02:58pm Aug 12, 2001 Pacific (#46 of
52) I think a lot of people are overlooking the fact that Dan is playing
with a stacked deck here. I very much doubt that his “tests”
start out with a raw scan from an 8-bit capture device. At very least,
black and white points are probably being set in the scanner, probably in
12-bit space. Maybe some rough tonal shaping too.
In which case, the debate simply becomes one of
whether it’s advantageous to do gross corrections in the scanner
software or in Photoshop.
I started using a primarily 16-bit workflow primarily
because most scanner software did such an abysmal job of transferring color
correctly to Photoshop, and because I don’t like making critical
image decisions on a postage-stamp-sized prescan.
From a quality standpoint, it makes little difference
whether you carry out the manipulations on the high-bit data in the scanner
software or in Photoshop. I prefer doing it in Photoshop because it gives
me more control than most scanner software (or maybe, honestly, because I
know Photoshop’s controls better than I know any scanner software),
and because I can see every pixel in Photoshop.
If you really start out with a RAW image in high-bit
form and a raw image downsampled to 8 bits, the difference really is night
and day. But very few people do anything of the kind.
Those of us who have adopted a 16-bit workflow in
Photoshop have done so because we’re less likely to make dumb moves
based on the postage-stamp preview, and because high-bit files in Photoshop
give us much more editing flexibility and headroom than an 8-bit file
produced from manipulating high-bit data on a scanner or digital camera.
But if someone prefers to do the gross manipulations in the scanner or
camera software, I won’t argue with them. It doesn’t really
matter, beyond personal preference and skills, where one manipulates the
high-bit data.
But it’s totally obvious to anyone who looks
that it’s very advantageous to do the big moves on high-bit data.
*********************************
___________________________________________________________________________
Date: Sun, 14 Nov 2004 10:29:59 -0500
From: “Iliah Borg”
Subject: Re: Color bit depth
On Sun, 14 Nov 2004 10:03:21 EST
Dan Margulis wrote:
I thought that such a thing would happen myself, which
is why I included
exactly such images in my tests. To my surprise, there
was no advantage to editing
in 16-bit even in such an extreme case. If anybody
else has tried a
side-by-side test on such an image and gotten a
different result,
I’d be happy to hear about it.
I’m afraid that rather crude math used in some
image editing programs may be one of the reasons.
Best regards,
ib
___________________________________________________________________________
Date: Sun, 14 Nov 2004 10:22:18 -0700
From: Andrew Rodney
Subject: Re: 16 Bit images only into LAB color space
on 11/14/04 8:00 AM, Dan Margulis wrote:
The argument concerns Andrew’s revisionist
claims that he has never heard
anyone (like, for example, his own business partners)
say that correction in
16-bit creates a night-and-day difference, or that
anyone who doesn’t workthat
way is a recreational as opposed to a professional
user.
No, I said I never said that and challenged you to
quote me on saying that. Big difference.
And, as Andrew’s later post shows, neither
this
person nor anybody else in their right mind would say
such a thing today. I trust
this brings this episode to a close.
That1s an assumption only Dan would make. I suggest
you contact Mr. Schewe and see if indeed he1s of that belief or not. I
posted a reasonable and rational response from Bruce Fraser from that 2001
post. But again, you1ll have to ask Bruce if he still feels that way or
not. Unlike some, I try not
to put words in other people1s mouth or misquote.
This debate which has gone on for years in this and
other forums is simply getting to the point that it1s like a religious
belief of both parties. It1s pointless.
Here are some facts and some color theory:
Fact. Nearly all tone and color corrections (color
space conversions included) cause data loss. It1s simple math. This can1t
be disputed. The question becomes can anyone see this data loss? See it
where? On what output device? At one point in the editing process? The fact
that data loss happens is not something that should keep users awake at
night worrying about but it should be something they recognize.
You1re taking an image and printing out to a halftone
dot once (as far as you1re concerned). Should you be alarmed that editing 8
bit data will cause data loss and be seen? From some or the more open
minded users who have posted on this subject, the answer based on their
experiences is clearly no. They point out that 16 bit files take up double
the file size and slow down processing and workflow and demand more storage
space. Now space isn1t a big issue for some, it is for others. Processing
speeds are getting faster all the time but none the less, that cost money
and takes time. Some have pointed out that the editing options in 16 bit
are less then 8 bit. True indeed. Not theory, fact. Photoshop CS opened up
a lot more options in respect to what users can do in 16 bit. That doesn1t
alter the facts about workflow, speed and storage.
Now despite the fact that some only view the world in
CMYK ink on paper, it1s a fact that some users have far greater needs from
their data. There are users who like Mr. Schewe will not only be doing on
going editing to images and printing them out to all nature of devices we
have today, but devices that are now in the lab. In 2001, when the quotes
above were made, there were few devices that would actually accept and use
16 bit data at print time. Today I can drive my 2200 with a RIP
(ImagePrint) that supports, uses and produces better results from 16 bit
files. I didn1t know this would be possible in 2001. I don1t know what will
be possible in 2006. IF my goal is to have a file that retains as much
useful data today and in the future (which is far cry from the service
bureau or print shop), my needs are vastly different.
Let1s not forget what1s coming (very soon) for some
users. HDR! An example can be seen here:
http://www.ict.usc.edu/graphics/HDRShop/
Some users produce imagery that requires by their
choice the least amount of data loss in order to keep the data as pristine
as possible for present and future uses. Others don1t care and have to
handle data quickly and move on. NEITHER is right for the other user. One
does paint the user into a lesser corner then the other. That1s not a color
theory, that1s a color fact. This argument over bit depth is like the
current argument now in vouge (shoot RAW or let the camera process the RAW
data on the fly and toss the RAW away).
The latest take on high bit editing I1ve seen from
Bruce Fraser is in his fine book “Real World Camera RAW2 page 8. It
takes both debates and puts them into a useful perspective:
3Don1t be overly afraid of losing levels-it1s a normal
and necessary part of image editing, and it1s effect can be greatly reduced
by bringing images into Photoshop in 16 bit/channel files rather then 8
bit/channel ones-but simply be aware of the destructive potential Photoshop
edits.2
Andrew Rodney
http://digitaldog.net/
___________________________________________________________________________
Date: Sun, 14 Nov 2004 10:19:08 -0800
From: Paul DeRocco
Subject: RE: Color bit depth
From: Dan Margulis
I thought that such a thing would happen myself, which
is why I included
exactly such images in my tests. To my surprise, there
was no
advantage to editing
in 16-bit even in such an extreme case. If anybody
else has tried a
side-by-side test on such an image and gotten a
different result,
I’d be happy to hear
about it.
16 bits allows you to pile more changes on top of each
other without accruing round-off errors. You can make some global edit
(e.g., Curves, Levels, Hue/Sat, etc.), then decide it’s not quite
right so make another edit, then another, then another, without worrying
about the fact that in 8-bit mode, each tweak can add up to half an lsb
worth of quantization noise in some areas. In most images it won’t
matter, but it frees you from worrying that you’re approaching the
point where you’re v