Date: Fri, 31 May 2002 21:44:50 EDT
From: psthree@aol.com
Subject: CMYK JPEG Bug
Hello all
What do you folks think about this?
A lot of my customers are asking me about it
Peter Stema
> Photoshop CMYK to JPEG bug? A reader described a problem with CMYK images in
> Photoshop (see also previous related item): "I discovered that Photoshop 7
> after having saved a CMYK image to JPEG and then closing and reopening the
> file to examine it had converted the white areas from 0C,0M,0Y,0K to
> 1C,1M,1Y,0K. It does this regardless of color settings or JPEG settings and in
> OS 9 or OS X. Two of my associates who tried this found the same problem. The
> only way I could accurately save the file in JPEG format was to revert to
> Photoshop 6."> Update: Ken Harris replies: "Having been in the pre-press industry for far too
> many years, I can honestly say that I know of no press in the printing
> industry capable of printing a screen value of 1% and it's doubtful that these
> values would even be perceptible to the human eye. If the saved JPEG file is
> to be used for printing I can't see how the final printed image would be
> affected."> Update: However, another reader adds: "This could be part of a larger issue in
> Photoshop 7 and 6 in the changing of color modes. I have found that any
> conversion between RGB, CMYK, Grayscale, or LAB results in solid areas of
> color becoming dithered. Try this as an exercise:> 1. Create a new document (any size, any color mode except bitmap)
> 2. Fill the canvas with any color besides black or white
> 3. Now change the color mode (anything except bitmap)
> 4. Go to Select>Color Range and select the canvas with a fuzziness of 0
> 5. You'll find that Photoshop has changed your solid-colored into a dithered
> canvas.
>
> This but wasn't around in version 5, and is quite annoying for photo or design
> that contains a solid area of color."
Date: Sat, 01 Jun 2002 16:54:41 -0000
From: Stephen Marsh
Subject: Re: CMYK JPEG Scum White
There is a thread in the Adobe Photoshop user forum about this -www.adobeforums.com/cgi-bin/webx?50@105.SsAlaIgeCwG^1@.ef8db3d
The Adobe response so far seems to be that CMYK users should be thankful that Photoshop offers the support for CMYK JPEG.
CTP with 1% CMY whites next to clean paper white in various printing conditions might very well show this, where film would probably not hold this to plate.
Checking for scum dots is just one of those things you get used to - but it does not mean that you like it. This presumes that you actually have the opportunity to run your mouse/info palette over the final converted CMYK data, or perhaps inspect histograms or levels or whatever.
The dither issue is a different story to the JPEG problem. Unless high bit edits that are reduced to regular bit in Photoshop are used - the dither for mode transforms can be disabled under the Advanced colour settings options (high bit dither can't be disabled).
Stephen Marsh.
Date: Sat, 1 Jun 2002 12:46:18 EDT
From: Dan Margulis
Subject: Photoshop 7 CMYK JPEG bug
Peter Stema writes,>>"I discovered that Photoshop 7 after having saved a CMYK image to JPEG and then closing and reopening the file to examine it had converted the white areas from 0C,0M,0Y,0K to 1C,1M,1Y,0K. It does this regardless of color settings or JPEG settings and in OS 9 or OS X. Two of my associates who tried this found the same problem. The only way I could accurately save the file in JPEG format was to revert to Photoshop 6." >>
I've confirmed that this exists in Photoshop 7 and does not exist in Photoshop 6. For those affected, it's a serious bug.
What is happening is that there's a one-level, not one percent, difference. So, the file is actually calling for a half-percent dot in cyan, magenta, and yellow.
The quote that one percent dots aren't commonly held is completely wrong, more so today in the age of direct-to-plate than it was, say, five years ago. Today, most commercial printers at least have something there, and even some newspapers do. Worse, some poorer-quality firms, particularly flexo printers, have look-up tables that jack up all highlight dots to something their press can hold. So, the RIP of such a flexo printer is apt to interpret that one-level difference as a 5% dot.
The problem is not in unretouched pictures; nobody is going to care if zeroed-out areas are exactly zero. The problem is when an image is silhouetted and placed into a page layout program against an otherwise blank background. In that case, the invisible box holding the image won't be invisible any more. I'm aware of one newspaper that had to issue a very large credit for a full-page ad that had this effect--the client supplied an RGB file where the background was 255r255g255b, and the color management system that the newspaper was then experimenting with converted it to 1c1m1y just as here, and the newspaper press held the 1% dot.
This has been a major bug in certain iterations of color management engines. Generally, the ICC and the vendors haven't realized that this is not just an inconvenience but a crippling problem for those it affects. Chris Murphy, in particular, has been very strong in criticizing those who don't realize that a one-level difference usually isn't important, *except* when the user is expecting pure white, when it's critical.
Dan Margulis
Date: Sat, 1 Jun 2002 11:49:48 -0600
From: Chris Murphy
Subject: Re: Photoshop 7 CMYK JPEG bug
Dan Margulis writes:>This has been a major bug in certain iterations of color management engines.
It may be a bug in the engines also, but I think it's also a bug in how the profile is built. In any event, that is definitely NOT the problem in this case. This is a file save bug that affects JPEG compressed files whether they are JPEG images or TIFF images with JPEG compression.
To test, you don't even have to convert an image to CMYK, just make a new CMYK document with whitebackground. Clearly this would be an image containing 0,0,0,0 CMYK values, and it does. But upon saving with JPEG, then reopening in anything that will let you read those values, they are now 1% each of CMY. If you save it as a TIFF with JPEG compression, you get 1% each of CMYK.
Basically you will need to avoid the JPEG format, and JPEG compression of any kind in Photoshop 7 in conjunction with CMYK images.
Chris Murphy
Color Remedies (tm)
Boulder, CO
303-415-9932
Date: Sat, 1 Jun 2002 11:55:45 -0600
From: Chris Murphy
Subject: Re: Photoshop 7 CMYK JPEG bug
Also, I am able to reproduce this bug in Photoshop 6 as well. It appears to be JPEG artifacting that's causing it, although I would expect a reasonable implementation of any lossless *OR* lossy (in the case of JPEG) compression to ensure certain values are retained exactly - 0% and 100% being one of them.Chris Murphy
Color Remedies (tm)
Boulder, CO
303-415-9932
Date: Sat, 1 Jun 2002 12:08:03 -0600
From: Chris Murphy
Subject: Re: Photoshop 7 CMYK JPEG bug
OK back the train up. It doesn't affect everything that uses JPEG compression. This problem does not occur with EPS files using JPEG compression with either High Quality or Maximum Quality. It does occur to some degree (1% in two channels) with Medium Quality and Low Quality.I don't understand how it's possible for Adobe to pin the blame on JPEG compression when it does not occur using High Quality or Maximum Quality JPEG compression with EPS files. Yet with the same quality setting, it does happen to both JPEG file format, and TIFF file format with JPEG compression.
Chris Murphy
Color Remedies (tm)
Boulder, CO
303-415-9932
Date: Sat, 01 Jun 2002 13:47:39 -0600
From: Andrew Rodney
Subject: Re: Photoshop 7 CMYK JPEG bug
on 6/1/02 11:55 AM, Chris Murphy wrote:> Also, I am able to reproduce this bug in Photoshop 6 as well. It appears
> to be JPEG artifacting that's causing it, although I would expect a
> reasonable implementation of any lossless *OR* lossy (in the case of
> JPEG) compression to ensure certain values are retained exactly - 0% and
> 100% being one of them.Just for grins I tried this using compression with MrSid (which is sooooo much better than JPEG). After decompressing the file from 15:1 compression, the numbers were identical to the original (0/0/0/0).
Andrew Rodney
Date: Sat, 01 Jun 2002 17:06:33 -0400
From: Joey Benton
Subject: Re: Photoshop 7 CMYK JPEG bug
Let me briefly weigh in on this. In Photoshop 6 the same thing happens- sort
of When correcting a photo I set the highlight to be 2,1,1,0 and shadow to
55,45,45,95. After saving and re-opening the file the highlight becomes
2,1,2,0 and the shadow 56,46,45,95. By in large it is not a big deal and
I've chocked it up to lossy compression.Joey Benton
Salisbury Post
Date: Sat, 1 Jun 2002 15:21:29 -0600
From: Chris Murphy
Subject: Re: Photoshop 7 CMYK JPEG bug
For some reason, I'm no longer able to reproduce this bug in Photoshop 6. I've tried about 5 times and cannot get it to happen. So at this point I'm going to consider the one time I think I got it to happen as a fluke or bad procedure until I can consistently reproduce it. So it seems to be unique to Photoshop 7 at this point.Also, Michael Ornellas reports that the bug only occurs with JPEG compression of certain quality settings. For example, I consistently can reproduce the problem with quality factor 12 but it never happens with quality factor 8. I'm also able to reproduce the problem with and without an embedded profile. Some are reporting different results depending on Color Settings, what profile gets embedded in the file, and whether profiles are preserved, assigned, or assigned and converted on open. I haven't been able to reproduce this - I get the problem with Color Settings set to Color Management Off, or U.S. Prepress Defaults, and whether or not the file has an embedded profile.
Chris Murphy
Color Remedies (tm)
Boulder, CO
303-415-9932
Date: Sun, 02 Jun 2002 15:56:10 +0000
From: deranian@att.net
Subject: Re: Photoshop 7 CMYK JPEG bug
I think Mr. Benton is missing the problem here. This bug is not about the highlights and shadows , in other words the parts of the images you want to keep. It's about when white MUST be zero'd out for placement on a pure white background. Something we deal with every day in my studio.My question to Dan or anyone that is more connected to the "powers-that-be" at Adobe: How seriously are they taking these bug discoveries and inconsistencies like the color management issue everyone was up in arms about a few weeks ago? Has anyone at Adobe made any noise that they're looking into it? That a PS 7.0.1 update fixing these issues might be imminent? We are still a PS6 house, but I had planned to update all our workstations to MAC OS10 in late July and simultaneously update to all the latest (and not so greatest) Adobe software, like Illustrator 10 and Photoshop 7. I'm sure many of you show dogs have done this already. Any comments good or bad about your experience doing this? Any major downtime? Are you all happy now that you're in the new OS and running the latest Adobe has to offer? The list has focused on many specifics, I thought it would be good to hear more general impressions as well.
Warm Regards, to All,
-David Deranian
--
Digital Arts & Sciences, Inc.
Communication Arts for
the Digital Age
Date: Sun, 2 Jun 2002 08:48:41 EDT
From: Dan Margulis
Subject: Re: Photoshop 7 CMYK JPEG bug
Chris Murphy writes,>> I don't understand how it's possible for Adobe to pin the blame on JPEG compression when it does not occur using High Quality or Maximum Quality JPEG compression with EPS files. Yet with the same quality setting, it does happen to both JPEG file format, and TIFF file format with JPEG compression. >>
By now you should be aware that no matter how egregious the programming, no matter how naive the assumptions about real-world practices, no matter how sloppy the testing, no matter how poor the research, Chris Cox will find a way to blame it on everyone but the real culprit. The thing works in Photoshop 6. His programming team broke it in Photoshop 7. Simple as that.
>>Also, I am able to reproduce this bug in Photoshop 6 as well. It appears to be JPEG artifacting that's causing it, although I would expect a reasonable implementation of any lossless *OR* lossy (in the case of JPEG) compression to ensure certain values are retained exactly - 0% and 100% being one of them.>>
I can't reproduce it in Photoshop 6. BTW, this is *not* an artifacting problem. A pure white picture converts to 0c0m0y in PS6 and 1c1m1y in PS7.
Dan Margulis
Date: Sun, 2 Jun 2002 08:48:19 EDT
From: Dan Margulis
Subject: Re: Re: CMYK JPEG Scum White
Stephen writes,>>There is a thread in the Adobe Photoshop user forum about this - The Adobe response so far seems to be that CMYK users should be thankful that Photoshop offers the support for CMYK JPEG. >>
I checked the thread, and that's about the gist of it. The argument is as I described before: since you can't be sure that *any* color is going to be portrayed accurately you shouldn't be surprised that 0=1, and if you don't like it you shouldn't use JPEG.
Unfortunately, this is par for the Adobe course. There's no real-world experience on the programming team, and they won't listen to the experts, and so they really have no clue that it's an issue that silhouetted areas can't have any dot, or that doubling file sizes in Photoshop format is a major minus, or that if unsophisticated users start employing unusual TIFFs it's likely to blow up in their faces, or that having to respond to hundreds of bogus Save Changes warnings a day is a problem.
The arrogant response to something that is so obviously a programming flaw is only another symptom. There is plainly talent on the programming team: this is a bad bug, but still, Photoshop releases typically have fewer bugs than those of say, Illustrator or QXP.
This fish, however, stinks from the head down. The Photoshop development team has lost its customer orientation, and the program quality has suffered. That's not the fault of the programmers but of the head or heads of the team. It is time that Adobe get rid of the management that allowed this to happen and put in more quality-conscious and customer-oriented supervision.
Dan Margulis
Date: Sun, 2 Jun 2002 11:05:54 -0600
From: Chris Murphy
Subject: Re: Photoshop 7 CMYK JPEG bug
deranian@att.net (deranian@att.net) writes:>My question to Dan or anyone that is more connected to
>the "powers-that-be" at Adobe: How seriously are they
>taking these bug discoveries and inconsistencies like the
>color management issue everyone was up in arms about a
>few weeks ago?There is no evidence that is going to change even though it benefits maybe 10 people's workflows, 8 of whom work at Adobe. While it's consistent behavior philosophically from one perspective, it's not consistent with most people's expectations or needs. Anyway, unless Adobe gets a bunch of tech support calls complaining about it, it's not going to change.
> Has anyone at Adobe made any noise
>that they're looking into it? That a PS 7.0.1 update fixing
>these issues might be imminent?There will be a 7.01 update sometime this summer I expect.
> We are still a PS6 house,
>but I had planned to update all our workstations to MAC
>OS10 in late July and simultaneously update to all the
>latest (and not so greatest) Adobe software, like
>Illustrator 10 and Photoshop 7. I'm sure many of you
>show dogs have done this already.Like maybe 5%. You'd definitely be on the bleeding edge. If you're going to wait until July, I'd wait a little longer. A major major update, "Jaguar" is due in early to mid-September that will bring tons of fixes (and no doubt a few problems as well). So I would be looking at early to mid-October for transitioning, and do it with that version of OS X. If you want to do it sooner, then I wouldn't wait for July. There's nothing special happening in July. You might as well just start transitioning the truly early adopters now and see how things go - or postpone until a month after Jaguar is released. That's my opinion.
Chris Murphy
Color Remedies (tm)
Boulder, CO
303-415-9932
Date: Sun, 2 Jun 2002 10:59:54 -0600
From: Chris Murphy
Subject: Re: Photoshop 7 CMYK JPEG bug
Dan Margulis writes:>I can't reproduce it in Photoshop 6. BTW, this is *not* an artifacting
>problem. A pure white picture converts to 0c0m0y in PS6 and 1c1m1y in PS7.I'm not having a conversion problem. Just make a new document, CMYK mode, white background and save it with anything using JPEG compression except for EPS and you get the problem, but apparently only in Photoshop 7. The only time I can successfully reproduce something like this in Photoshop 6 is with really low quality compression.
Chris Murphy
Color Remedies (tm)
Boulder, CO
303-415-9932
Date: Sun, 2 Jun 2002 17:17:36 -0400
From: "Preston Earle"
Subject: Re: Photoshop 7 CMYK JPEG bug
"Chris Murphy" wrote:
"To test, you don't even have to convert an image to CMYK, just make a new CMYK document with white background. Clearly this would be an image containing 0,0,0,0 CMYK values, and it does. But upon saving with JPEG, then reopening in anything that will let you read those values, they are now 1% each of CMY. If you save it as a TIFF with JPEG compression, you get 1% each of CMYK."
-------------------I can't duplicate this on my system (WinME, PS7). When I save the 0cmyk document as any level jpeg and reopen it, it is still 0cmyk. What am I missing? Is this a Mac-only phenomena?
If I save a 1c1m1y0k document at Level 0 jpeg compression, it becomes 2c2m2y0k, but at Level 6 compression it is 1c1m1y0k.
Preston Earle
PEarle@triad.rr.com
Date: Sun, 2 Jun 2002 16:43:37 -0600
From: Chris Murphy
Subject: Re: Photoshop 7 CMYK JPEG bug
Preston Earle writes:>I can't duplicate this on my system (WinME, PS7). When I save the 0cmyk
>document as any level jpeg and reopen it, it is still 0cmyk. What am I
>missing? Is this a Mac-only phenomena?It might be. I don't have access to a Windows version of Photoshop 7. One apparent Mac user on the Adobe forums can't get it to occur either.
Chris Murphy
Color Remedies (tm)
Boulder, CO
303-415-9932
Date: Sun, 2 Jun 2002 22:09:06 -0400
From: "Russell Proulx"
Subject: Re: Photoshop 7 CMYK JPEG bug
On 2 Jun 2002 at 17:17, Preston Earle wrote:> I can't duplicate this on my system (WinME, PS7).
I too see no evidence of the problem on my Win2000, PS7 system.
CMYK files containing a 0.0.0.0 value and saved in every compression value of JPG format I've tried are still 0.0.0.0 when reopened.
ie: file is unchanged
Russell Proulx
Date: Mon, 3 Jun 2002 00:25:21 -0700
From: Rick Gordon
Subject: Photoshop 7 CMYK JPEG Bug Tests
Testing in PS 7 running on OS X 10.1.3, I find an interesting pattern. Saving an image at levels 6 or 4, with either baseline standard or baseline optimized produces no scum dots but saving at levels 7 or 5 does produce scum dots. I haven't yet one further with this, but wonder if there may be a pattern of problems related to saving at odd-numbered levels.Any corroboration?
Rick Gordon
___________________________________________________
RICK GORDON
EMERALD VALLEY GRAPHICS AND CONSULTING
___________________________________________________Date: Mon, 03 Jun 2002 07:17:54 -0600
From: Ron Kelly
Subject: bad programming
Dan and All:
I've made comments before about the dangers of having all the eggs in one basket.It seems that people are reluctant to admit this. Why? Because they fear raising the hackles of Adobe? Who knows.
The digital universe seems to snuff out all evolutionary competition in favour of one option only. Just look at desktop operating systems.
Well, this list is supposed to address specific issues and not just general problems, and so here is my specific question: what is the best program OTHER than Photoshop for doing color correction/output?
Or is this list indeed joined at the hip to these arrogant managers?
Ron Kelly
Dan Margulis wrote:
>This fish, however, stinks from the head down. The Photoshop development team
> has lost its customer orientation, and the program quality has suffered.
> That's not the fault of the programmers but of the head or heads of the team.
> It is time that Adobe get rid of the management that allowed this to happen
> and put in more quality-conscious and customer-oriented supervision.
Date: Mon, 3 Jun 2002 07:42:22 -0600
From: Chris Murphy
Subject: Re: Photoshop 7 CMYK JPEG Bug Tests
Rick Gordon (rick@rickgordon.com) writes:>Testing in PS 7 running on OS X 10.1.3, I find an interesting pattern.
>Saving an image at levels 6 or 4, with either baseline standard or
>baseline optimized produces no scum dots but saving at levels 7 or 5 does
>produce scum dots. I haven't yet one further with this, but wonder if
>there may be a pattern of problems related to saving at odd-numbered levels.
>
>Any corroboration?Yes. 4, 6, and 8 do not have the problem. 9, 10, 11, 12 have the problem. Below 4 I'm not sure what the pattern is, but others have experienced it as well. The same pattern doesn't apply to PDF and JPEG. So I'm convinced this is a Mac only bug with a certain aspect of JPEG implementation in Photoshop 7. It's not a JPEG artifact or compression issue.
Chris Murphy
Color Remedies (tm)
Boulder, CO
303-415-9932
Date: Mon, 3 Jun 2002 10:48:13 -0400
From: "Pylant, Brian"
Subject: RE: Photoshop 7 CMYK JPEG bug (Windows)
> I too see no evidence of the problem on my Win2000, PS7 system.
>
> CMYK files containing a 0.0.0.0 value and saved in every
> compression value of
> JPG format I've tried are still 0.0.0.0 when reopened.Definitely happens here (PS 7, Win2K). I created a new CMYK image @ 300ppi, filled with c0 m0 y0 k0, saved as a JPEG at level 7, reopened and got c1 m1 y1 k0.
Now, I do have question: perhaps I'm old-fashioned (imagine that, I'm only 30!), but I never (EVER!) use a JPEG for print output (even at the highest quality settings), so this problem would never affect me or my workflow at all. Are more people moving towards using JPEGs for print output? I was always taught, and always advise my clients, that this is a BIG no-no; in these days of dirt cheap storage, high-bandwidth transfers and CD-Rs in nearly every machine, using JPEG compression for non-web purposes seems irrelevant IMO.
Of course a bug is still a bug, and a poor response from Adobe (which is sadly becoming more and more frequent) is still irritating at best and their lack of concern is appalling, but that's a different discussion altogether.
Brian
Date: Mon, 03 Jun 2002 11:39:01 -0400
From: "Owen Colborne"
Subject: jpeg numbers in PS&, OSX
I just ran a series of saves in OS 10.1.4 and PS7 with the following
results
jpeg compression
level cmyk values
0 0 0 0 0
1 0 0 0 0
2 1 1 10
3 0 0 0 1
4 0 0 0 0
5 1 1 1 0
6 0 0 0 0
7 1 1 1 0
8 0 0 0 0
9 1 1 1 0
10 1 1 1 0
11 1 1 1 0
12 1 1 10I also ran eps with jpeg compression as follows
jpeg low 0 1 1 0
jpeg med 1 0 0 1
jpeg hi 0 0 0 0
jpeg max 0 0 0 0Owen Colborne
Digital Photography Specialist
Que-NET Mediaª
a Member of the Quebecor World Group
Date: Mon, 3 Jun 2002 11:50:56 -0400
From: "Preston Earle"
Subject: JPEG compression Was: Photoshop 7 CMYK JPEG bug (Windows)
"Pylant, Brian" wrote:
"Now, I do have question: perhaps I'm old-fashioned (imagine that, I'm only 30!), but I never (EVER!) use a JPEG for print output (even at the highest quality settings), so this problem would never affect me or my workflow at all. Are more people moving towards using JPEGs for print output? I was always taught, and always advise my clients, that this is a BIG no-no; in these days of dirt cheap storage, high-bandwidth transfers and CD-Rs in nearly every machine, using JPEG compression for non-web purposes seems irrelevant IMO."
-----------------
Brian, as you get older (I'm almost 60), I think you'll find the "dangers" of JPEG, like many other "dangers" (you fill in the blanks) are over-rated. For offset print images with adequate resolution (>1.5 pixels per halftone-dot), I don't believe you will ever see and effects of JPEG compression for Photoshop JPEG's saved with Level 6 or higher compression, this current debate not-withstanding. There is an issue of whether RIP's can process JPEG's, and there may be older RIP's in the field which have a problem with JPEG's, so from that perspective, TIFF's are saver.My rule of thumb is based on the "value" of the image. For High Value images, I'd keep everything in TIFF format, "just to be safe". For Low Value images, I'd save the storage space and go with medium JPEG compression. Of course, what's High Value and what's Low Value is up to you.
Several years ago, when storage space was more expensive, a company I was associated with need to provide an image database on CD of more than a thousand high-resolution images for a major furniture manufacturer. We did considerable testing and found no one could tell Level 6 JPEG's from TIFF's (based on Matchprint proofs of each). We decided that getting 320 JPEG's on a CD was better than getting 32 TIFF's. YMMV.
I'm interested to see what other tests have been done in this area and want they showed.
Preston Earle
PEarle@triad.rr.com
Date: Mon, 3 Jun 2002 13:09:47 -0400
From: "Russell Proulx"
Subject: RE: Photoshop 7 CMYK JPEG bug (Windows)
On 3 Jun 2002 at 10:48, Pylant, Brian wrote:> Definitely happens here (PS 7, Win2K). I created a new CMYK image @
> 300ppi, filled with c0 m0 y0 k0, saved as a JPEG at level 7, reopened and
> got c1 m1 y1 k0.Oops... my apologies. Yes, I did the above and YES it did occur
ie: saving cmyk 0.0.0.0 in jpg-7 DID become 1.1.1.0 upon re-opening.
I spoke too soon ... what else is new ..<g>
Russell
Date: Mon, 3 Jun 2002 10:36:27 -0700
From: David Cardinal
Subject: JPEG compression Was: Photoshop 7 CMYK JPEG bug
> Several years ago, when storage space was more expensive, a
> company I was associated with need to provide an image
> database on CD of more than a thousand high-resolution images
> for a major furniture manufacturer. We did considerable
> testing and found no one could tell Level 6 JPEG's from
> TIFF's (based on Matchprint proofs of each). We decided that
> getting 320 JPEG's on a CD was better than getting 32 TIFF's. YMMV.
>
> I'm interested to see what other tests have been done in this
> area and want they showed.Preston--Your results are very similar to what we have found as well. In writing an article on file formats for the BT Journal I tried hard to demonstrate what it would take to cause JPEG artifacts that are noticeable in a 4-color press output. I found I had to re-save an image about 8 times and then magnify it for production to create a situation where the artifacts were obvious.
Clearly I could have used Low quality JPEG settings and gotten this effect much more quickly, but the article was for photographers and the assumption was that they would be using either Fine mode on the camera or 8 or better in Photoshop.
I'm going through the process again for an eBook we're doing, and find that I have to use test targets and then amplify the "noise" caused by JPEG compression to get any visible artifacting at the higher (10-12) levels.
--David Cardinal
http://www.nikondigital.org
http://www.proshooters.com
Date: Mon, 3 Jun 2002 11:55:06 -0600
From: Chris Murphy
Subject: Re: jpeg numbers in PS&, OSX
Owen Colborne (owen.colborne@quebecorworld.com) writes:
>I just ran a series of saves in OS 10.1.4 and PS7 with the following
>results
>jpeg compression
>level cmyk values
>0 0 0 0 0
>1 0 0 0 0
Yes for JPEG. No for TIFF with JPEG compression. I get scum dots with Quality value 0 and 1; also OS 10.1.4, and PS 7, with color settings set to U.S. Prepress Default (except I doubt that has anything to do with it).
The values common to JPEG and TIFF with JPEG compression that don't exhibit the problem are 4, 6, and 8.
Chris Murphy
Color Remedies (tm)
Boulder, CO
303-415-9932
Date: Mon, 03 Jun 2002 12:06:42 -0700
From: Kevin Connery
Subject: JPEG for press usage
"Pylant, Brian" wrote:> Now, I do have question: perhaps I'm old-fashioned (imagine that, I'm only
> 30!), but I never (EVER!) use a JPEG for print output (even at the highest
> quality settings), so this problem would never affect me or my workflow at
> all. Are more people moving towards using JPEGs for print output? I was
> always taught, and always advise my clients, that this is a BIG no-no; in
> these days of dirt cheap storage, high-bandwidth transfers and CD-Rs in
> nearly every machine, using JPEG compression for non-web purposes seems
> irrelevant IMO.Given that JPEG was a compression method designed to permit transferring and storing large photographic files--primarily expected to be used for print output--this is a bit of an over-reaction.
It's only been recently (~5-7 years) that it's been mostly a low-resolution tool for the web; the originally intended use of JPEG was exactly what you're advising people against.
Whether it's still appropriate is a different question.
--kdc/Kevin Connery
Date: Mon, 3 Jun 2002 15:28:35 -0400
From: "Pylant, Brian"
Subject: RE: JPEG compression Was: Photoshop 7 CMYK JPEG b ug (Windows)
> Brian, as you get older (I'm almost 60), I think you'll find the
> "dangers" of JPEG, like many other "dangers" (you fill in the blanks)
> are over-rated. For offset print images with adequate resolution (>1.5
> pixels per halftone-dot), I don't believe you will ever see
> and effects
> of JPEG compression for Photoshop JPEG's saved with Level 6 or higher
> compression, this current debate not-withstanding.Agreed, of course - I guess my basic feeling is that any sort of file compression is unnecessary given today's storage medium, network capacities and 'net connections, especially lossy compression (whether you can see the loss or not). Not counting distributed image libraries, of course (stock photography, etc.) - that is a situation where you need to keep a high files-per-disc count (note that when I use one of these images in a layout one of the first things I do is resize/crop and save as a TIFF!).
Good point about the RIPs, too -- I know ours (Artwork Systems/PCC Pageflow) chokes on any JPEG compression so we've definitely gotten in the habit or resaving supplied files as TIFFs or EPSs before output.
Brian
Date: Mon, 3 Jun 2002 15:02:17 -0500
From: "Broudy, David"
Subject: RE: Photoshop 7 CMYK JPEG bug (Windows)
yep, same thing here w/PS7 and Win2k, level 5 jpeg crunching w/defaults, doesn't matter if a cmyk profile is embedded or not. whee!
--
David Broudy
Jostens R&D
11300 Rupp Drive
Burnsville, MN 55337
952.882.3617
> Oops... my apologies. Yes, I did the above and YES it did occur
>
> ie: saving cmyk 0.0.0.0 in jpg-7 DID become 1.1.1.0 upon re-opening.
Date: Mon, 3 Jun 2002 16:12:45 EDT
From: jtytel@aol.com
Subject: eps or tiff
If I may, I need some input on providing tiff or eps files.I shoot digital commercial work and I handle all the conversions for pre-press and I provide my clients with eps or tiff files. In the past when clipping paths for Quark were needed we always provided eps files. I understand that Quark can also utilize tiff files with a clipping path. So, I have been providing eps files in the following instances:
1) When there is a clipping path needed for outline
2) When there is a gradation or vignette in the photograph
3) For sending eps (with jpeg compression) over the web
Is there any other reasons for providing an eps file that anyone may suggest.Thank you for your answers.
Jeff Tytel
Date: Tue, 4 Jun 2002 09:25:25 EDT
From: Dan Margulis
Subject: Re: JPEG compression
Preston writes,>>I think you'll find the "dangers" of JPEG, like many other "dangers" (you fill in the blanks) are over-rated. For offset print images with adequate resolution (>1.5 pixels per halftone-dot), I don't believe you will ever see and effects of JPEG compression for Photoshop JPEG's saved with Level 6 or higher compression, this current debate not-withstanding. There is an issue of whether RIP's can process JPEG's, and there may be older RIP's in the field which have a problem with JPEG's, so from that perspective, TIFF's are saver... I'm interested to see what other tests have been done in this area and want they showed.>>
All tests reported so far don't show a significant quality difference on output, but then again they all test by making the JPEG directly from the final output file. If the JPEG is made early in the process and there is then extensive correction, for sure one can't use the yellow channel for blending any more, and there may be other consequences as well.
But, so many files come in as JPEGs now that there isn't much that can be done about it.
Dan Margulis
Date: Tue, 4 Jun 2002 09:26:05 EDT
From: DMargulis@aol.com
Subject: Re: Photoshop 7 CMYK JPEG bug
Brian writes,>>Are more people moving towards using JPEGs for print output? I was always taught, and always advise my clients, that this is a BIG no-no; in these days of dirt cheap storage, high-bandwidth transfers and CD-Rs in nearly every machine, using JPEG compression for non-web purposes seems irrelevant IMO.>>
Not if you have to transmit lots of big files to and from clients. Bandwidths aren't *that* high.
Also, a number of larger operations JPEG their CMYK files before archiving them, at least if they doubt that they'll ever use them again. Sure, storage is cheap, but backup time isn't, and setting up ten times as many directories as needed to hold terabytes of unnecessary information isn't efficient.
Dan Margulis
Date: Tue, 04 Jun 2002 10:44:48 -0600
From: Ron Kelly
Subject: Re: Re: JPEG compression
Dan Margulis wrote:> All tests reported so far don't show a significant quality difference on
> output, but then again they all test by making the JPEG directly from the
> final output file. If the JPEG is made early in the process and there is then
> extensive correction, for sure one can't use the yellow channel for blending
> any more, and there may be other consequences as well.Hi Dan:
Let me ask you this: do you have your digital camera set to write in "RAW" mode or jpeg? I haven't used one of these units yet but I will make the change soon. I'm trying to understand how important it may be to have lots of storage in the camera (I'm interested in the highest possible quality, even at the expense of speed to write to the storage media.) Many camera salesmen will say that there is virtually no need to use RAW format as a print will not show any difference vs. a "fine" jpeg.Ron Kelly
Date: Tue, 4 Jun 2002 14:46:36 EDT
From: Dan Margulis
Subject: Re: bad programming
Ron Kelly writes,>>It seems that people are reluctant to admit this. Why? Because they fear raising the hackles of Adobe? Who knows.>>
That's one of the problems with the field generally, and does not pertain exclusively to Adobe. The most vocal people are "independent" consultants who can have rather incestuous relations with the vendors. This is particularly true on the ColorSync list, where one really can't tell who is taking money from whom to say what.
We've already had at least one outright shill defending Photoshop 7 here, but really everybody, even me, wants to be on Adobe's good side, whether we take money from them or not.
Fortunately, there are limits. You will observe that *nobody* outside of Adobe defends that stupid warning that they've imposed on users of layered Photoshop files, or the enticement of novices to use TIFF options they don't understand. And nobody outside Adobe is going to suggest that this JPEG thing is anything other than the bug it is.
>> Well, this list is supposed to address specific issues and not just general problems, and so here is my specific question: what is the best program OTHER than Photoshop for doing color correction/output?>>
Corel's PhotoPaint, which is now available for the Mac, has most of Photoshop's significant features and is designed with Photoshop users in mind.
>>Or is this list indeed joined at the hip to these arrogant managers?>>
First, I think the idea that I am joined at the hip to Adobe would come as a surprise to many people. Second, the key word is "arrogant." Nobody should be shocked that software as complex as Photoshop should ship with an esoteric bug like this, serious though it may be. If Adobe had just said, "We run an extensive beta program to catch stuff like this, but obviously it didn't do so in this case. We're really sorry. We will have this fixed in the next maintenance upgrade," I don't think anybody would have been upset.
Similarly, that Photoshop 7 has fewer new features than past versions would not cause much annoyance, except for the coercive changes, and the repetition of the arrogant attitude of the past that Adobe can dictate workflows to the market. One would have thought that the team leadership would have learned from the Photoshop 5 experience that this is not true. Since they are apparently incapable of learning from their mistakes, replacing them would be the sensible move for Adobe to make at this point.
Dan Margulis
Date: Tue, 4 Jun 2002 12:22:07 -0700
From: David Cardinal
Subject: RE: Re: JPEG compression
> Let me ask you this: do you have your digital camera set
> to write in "RAW" mode or jpeg?Ron--This is an incredibly disputed topic with lots of opinions. What we have seen (from using and writing about the D1/X/H, D30/60 and 1D, and corresponding with hundreds of owners) is that Raw mode is most important if you need to correct the exposure or white balance later.
If you have nailed the exposure & WB in the captured image then you can make large display quality prints from JPEGs, as the gamma/tone encoded 8-bits in the JPEG are quite effective in representing the important information from the 12-bit linear space.
However, if you really need to massage the exposure, WB, or the tonal range, then you have lost some of that flexibility with the JPEG encoding, so you tread on increasingly thin ice when you make those corrections later.
In many cases, wedding pros are using Raw because of tricky lighting and as insurance that they can print their key shots. Sports seems to be split depending on volume of images and timeframe (Raws of course take more space & require post-processing). Nature/Wildlife is mostly JPEG to capture fast action (although there is a vocal Raw minority there as well). Fine art photographers tend to use Raw because they can. Studio shooters are split, depending on client requirements.
That said, like all photo statistics or advice, whatever works for each individual is the right solution for them!
--David Cardinal
http://www.nikondigital.org
Pro Shooters LLC
http://www.proshooters.com
Date: Tue, 4 Jun 2002 12:28:15 -0700
From: Jan Steinman
Subject: Re: JPEG compression Was: Photoshop 7 CMYK JPEG bug (Windows)
>"Pylant, Brian" wrote:
>"Now, I do have question: perhaps I'm old-fashioned (imagine that, I'm
>only 30!), but I never (EVER!) use a JPEG for print output (even at the
>highest quality settings)...
>
>"Preston Earle" wrote:
>Brian, as you get older (I'm almost 60), I think you'll find the
>"dangers" of JPEG, like many other "dangers" (you fill in the blanks)
>are over-rated...I'll split the difference between you two, since I'm 46. :-)
I avoid JPEGs for more pragmatic reasons. They are often poorly handled in different workflows, and they do tend to have a "crud build-up" problem if repeatedly edited and saved, especially when re-sized, which one tends to do in multi-purpose workflows. (My tests show that, contrary to popular belief, minor editing and re-saving of an un-resized JPEG does little additional damage.)
I'll agree that a one-time compressed, high-quality JPEG is very fine indeed, and often "good enough" for a single purpose print output, but using these puppies for multiple purposes is just asking for trouble!
-- : Jan Steinman
: Bytesmiths
: 19280 Rydman Court, West Linn, OR 97068, 503.635.3229
Date: Tue, 04 Jun 2002 18:27:54 -0500
From: Bob Smith
Subject: Re: Re: JPEG compression
Ron Kelly wrote:> Many camera salesmen will say that there is virtually no need to use
> RAW format as a print will not show any difference vs. a "fine" jpeg.The difference lies in how much more you can alter the RAW file. If you process the RAW file to the exact same specs that the camera uses to produce a JPEG then yes, the difference is minimal. On the other hand, if you miss exposure by a couple of stop in either direction; or shoot in tungsten light with daylight balance selected, the RAW file is a major blessing. Having a JPEG file is much like having a good print to scan whereas having the a RAW file is like having the original negative. All of this of course is predicated on how good the camera's raw processing software is. JPEG workflow is ideal for speed. Its widely used in photojournalism applications. A RAW workflow is far more versatile at the expense of speed.
Bob Smith
Date: Wed, 5 Jun 2002 10:21:00 EDT
From: Dan Margulis
Subject: Re: JPEG compression
Ron Kelly writes,>>Hi Dan:
Let me ask you this: do you have your digital camera set to write in "RAW" mode or jpeg?>>JPEG, because I think there's little loss and because my personal style is to shoot lots of exposures and not care that most of them have to be trashed. I shoot in the field; I don't have unlimited storage space and I don't like to waste the battery of my laptop by spending many times longer than necessary downloading the images.
A studio photographer, OTOH, might well take a different view. A much higher percentage of his images will be usable; he has essentially unlimited storage space and battery usage is not an issue. He may or may not gain anything from using the raw setting but he certainly isn't hurt by using it.
Dan Margulis
Date: Wed, 05 Jun 2002 09:06:45 -0700
From: Kevin Connery
Subject: Re: JPEG compression
Expected post-processing of the image also has an impact. Even the best quality JPEG compression has some artifacts that can make certain selection steps less accurate. If the image is expected to be post-processed as a composite image, that can be an issue that can increase the manual work involved in post.
For global processing it's rarely an issue; for edge details, invisible-to-the-eye or not, it can be.
--kdc/Kevin Connery
> JPEG, because I think there's little loss and because my personal style is to
> shoot lots of exposures and not care that most of them have to be trashed. I
> shoot in the field; I don't have unlimited storage space and I don't like to
> waste the battery of my laptop by spending many times longer than necessary
> downloading the images.
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