Dan Margulis Applied Color Theory

Eliminating Pepper Dots

Eliminating Pepper Dots
    Posted by: "leicamike2000"
    Date: Tue Jun 20, 2006 9:14 am (PDT)

I have a 35mm Velvia50 that has hundrers of black dots when viewed at 100%.I converted to LAB then tried to apply Dust&Scratches filter to A and B but this doesn`t do anything to the dots.When I apply Dust&Scratches to the L channel this eliminates them but it also softens the image.What should I do?Am I doing something wrong?
Mike Sellers
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Re: Eliminating Pepper Dots
    Posted by: "Greg Welch"
    Date: Tue Jun 20, 2006 9:55 am (PDT)

Sounds like it was scanned with anti-newton spray. This leaves a very fine dust and is not suitable for hiRez scans

Greg Welch
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Re: Eliminating Pepper Dots
    Posted by: "Maris V. Lidaka Sr."
    Date: Tue Jun 20, 2006 11:09 am (PDT)

What scanner are you using to scan the film?  If it doesn't have an IR channel for Digital ICE, which would be the ideal method, try Polaroid's freeware "Dust & Scratch Removal Utility" (Win & Mac)

http: //www.polaroid.com/service/software/poladsr/poladsr.html

Maris V. Lidaka Sr.
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Re: Eliminating Pepper Dots
    Posted by: "J Walton"
    Date: Tue Jun 20, 2006 11:10 am (PDT)

On 6/20/06, leicamike2000  wrote:

  I have a 35mm Velvia50 that has hundrers of black dots when viewed at
100%.I converted to LAB then tried to apply Dust&Scratches filter to A
and B but this doesn`t do anything to the dots.

That's because the dots aren't color noise.

When I apply Dust&Scratches to the L channel this eliminates them but it also
softens the image.

 You may be able to find a setting that minimizes the softening, but there's always a trade off when doing D&S.

What should I do?

I can think of two things to do off-hand. First, dup your layer before applying D&S. Add a filled layer mask, and with a small brush in the mask apply the correction only to the dots.

The other thing you could do is use the healing tool the same way. I'd go for option #1, though. It should take you no more than 10-15 minutes.

-----
J Walton
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 Re: Eliminating Pepper Dots
    Posted by: "Paul Marriner"
    Date: Tue Jun 20, 2006 11:15 am (PDT)

Try a technique I reread this AM. In RGB run a dust and scratches filter to clean up as much as possible. Now return to the spotted version but set the history brush to the filtered step. Set the history brush on lighten in blend mode. Brush away the spots with a large brush (100% opacity). Worked for me on a dirty slide trial. Doesn't work with the L channel (at least not for me) as the lighten and darken modes are greyed.

cheers
Paul
--
Paul Marriner
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Re: Eliminating Pepper Dots
    Posted by: "jimrich"
    Date: Tue Jun 20, 2006 11:18 am (PDT)

On Tue, 20 Jun 2006 12:24:17 -0400, Greg Welch wrote

Sounds like it was scanned with anti-newton spray. This leaves a
very fine dust and is not suitable for hiRez scans
 
If Greg is correct about the anit-newton ring spray, then one solution is rescan the 35mm slide by placing masking tape over the sproket holes areas that would be placed on the glass or drum. Then tape the 35mm slide back on the scanner. Of course before doing all of this you would clearn off the 35mm original. This method barely raises the 35mm original above the glass or drum of the scanner to avoid anit-newton rings.

And if you have followed by instructions use care when removing the tape from the sproket holes. If you pull the tape off too fast you can tear the 35mm easily. And if that happens it is not a pretty picture anymore.

Thanks

Jim Rich
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Re: Eliminating Pepper Dots
    Posted by: "George Machen"
    Date: Tue Jun 20, 2006 12:57 pm (PDT)

Here's a quick & dirty trick that may wipe-out all the pepper dots in less than a minute:

Make a duplicate layer or copy & paste just a selection of the offending area.
Set the mode of the new upper layer to Lighten.
Select the Move tool.
Nudge one or two times with an arrow key.
Voila! They're gone.

Sometimes this works perfectly, and other times it makes things look bad; depends on the image.

For white "salt dots," use the Darken mode.

Worth a shot.

George Machen
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Re: Eliminating Pepper Dots
    Posted by: "James Hylands"
    Date: Tue Jun 20, 2006 1:30 pm (PDT)

If you are going to the trouble of re-scanning the trans. Mount it in a thin layer of parrafin oil, under a sheet of mylar. This will also fill in and eliminate any flaws in the emulsion. Take it from an ex scanner operator!

James Hylands
Research and Development
Photographic Technical Support
Pi Media
15 Benton Road
Toronto,ON M6M 3G2
{416} 248-5500 Ext. 599
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1b. Re: Eliminating Pepper Dots
    Posted by: "leicamike2000"0
    Date: Tue Jun 20, 2006 6:03 pm (PDT)

Greg,

It was scanned by me with a Leaf45.This is the only piece of film that I have that has this problem.

Mike Sellers
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Re: Eliminating Pepper Dots
    Posted by: "leicamike2000" msellers1@sbcglobal.net leicamike2000
    Date: Tue Jun 20, 2006 6:10 pm (PDT)

Maris,

It was taken about 1991.I thought it was Velvia but I just looked at
it and it is Kodak EPX-Ektachrome?I use the Leaf45.

Mike Sellers
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Re: Eliminating Pepper Dots
    Posted by: John Castronovo
    Date: Wed Jun 21, 2006 1:22 am (PDT)

If you rescan it, why not fluid mount it? One question though, are these dots not visible on the film at all, even with a sharp light source rather than on a light box?

john castronovo
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Re: Eliminating Pepper Dots
    Posted by: Stephen Marsh
    Date: Wed Jun 21, 2006 1:49 am (PDT)

Mike Sellers wrote:

I have a 35mm Velvia50 that has hundrers of black dots when viewed at
100%.I converted to LAB then tried to apply Dust&Scratches filter to A
and B but this doesn`t do anything to the dots.

As previously noted, luminance (black) will not be found in the AB channels - only colour noise.

When I apply
Dust&Scratches to the L channel this eliminates them but it also
softens the image.What should I do?Am I doing something wrong?

Are you running the filter globally to the whole image?

The D+S filter is usually best used with a selection, feathered (usually a loose natural freeform shape rather than say a rectangular marquee). From an article I wrote on spotting for my old website (I have not updated this article yet so no link, only the old text):

Dust & Scratch Filtering

* Small Spots - The Dust and Scratches filter is well suited for the task of removing small spots and specks and is far less destructive to image detail and grain than the despeckle filter.

* Avoid Global Filtering - The Dust and Scratches filter is not suited for global filtering and produces the best results using a subtly feathered selection area which contains both damaged and clean data.

* Filter Settings - Often a radius of 1-2 pixels is more than sufficient to remove small spots, with moderate to high value threshold settings such as 24 levels or higher - so that image detail or grain is not harmed and only the very small spots are removed.

* Add Noise - The add noise or other grain addition filters are run to separate or composite channels to subtly restore 'life' to the filter corrected area. Note that in CMYK mode small amounts of K noise may be added where no K currently exists, as the filter is not tied to the image profile or current work space settings. It is a simple matter to apply CMY noise if this is the case.

* Dedicated Hardware & Software - Some scanner hardware/software combinations have dedicated dust and scratch removal solutions, such as Applied Science Fictions 'ICE' software.

* PolaDSR Software - Mac and PC users have the option of using the free Polaroid Dust & Scratch Removal software which comes as a stand alone application and as a Photoshop plug-in. The stand alone application has many options and seems worthy of deeper exploration.

* Wacom PenTools - Wacom graphics tablet users also have the option of using the free Wacom PenTools plug-in which contains a 'Pen Duster' filter (similar in many ways to using history brush techniques as described below).

<Snip>

 History Brush & Layer Mask Techniques

* History Snapshot & Brush - Using a corrected filtered history snapshot as the source for the history brush, corrections are applied to a new transparent layer.

* Alternate Method - A duped filtered layer with a layer mask can yield the same results as the history brush technique. Using a layer and layer mask can be more flexible, although the file size will be larger.

* Remaining Damage - Often cloning or healing will be used to quickly clean up any left over spots that the history technique fails to address.
 
Offset Technique

* Float/Offset/Move - Another approach is to use duplicated layer content and the offset filter or the move tool and arrow keys to offset the duped layer content slightly to cover the underlying dust. Best used for large low frequency areas which do not contain important detail.

* Blend Modes - For light dust on dark backgrounds the layer could be set to darken mode, while for dark spots on lighter backgrounds lighten mode could be used.
 
Automating the Spotting Process

There can be times when you are presented scans that require major spotting - but there may not be the time or budget to give the images your best attention. Automating the spotting process can be the answer in these less than ideal situations. Some manual cleanup and editing will still be required, these techniques are used to reduce the total spotting work - not totally remove it. The addition of some minor sharpening after the automated spotting process can restore some of the appearance of sharpness that has been lost. Remember, this is not an ideal situation and the usual quality expectations do not apply.

Method 1 - Difference Masking:

This technique uses a difference mask in an attempt to isolate the dust spots, without filtering more critical image detail. Corrections are applied to a new layer for easy evaluation and editing.

* Dupe the background layer and filter the small dust spots while attempting to preserve image detail.
* Change this layer to difference blend mode.  
* Create an alpha channel based off the result of this difference data and refine the mask so that the white dust spots are approximately x1.5 - x2 the size of the original spots.
* Delete the difference blend layer as it is no longer required.
* Dupe the background layer and load the difference mask as a selection, perhaps hiding the selection edges. Run the dust and scratches and other filters as required to remove the dust spots. * The selection can be inverted and the excess layer data deleted before the selection is dropped, or a layer mask can be applied to reveal the corrections within the selection.
* Deselect, merge the spotting layer down into the original background layer and delete the alpha channel when you are finished.

Method 2 - Targeted Blending:

An excellent technique demonstrated by Dan Margulis at a Seybold seminar and on his Applied Colour Theory list can be modified for dust spotting. Variations on this technique are applicable to many retouching situations - including cosmetic smoothing of skin tones, grain or noise reduction and recovering overly sharpened images.

* Duplicate the background layer and filter to remove the lighter coloured dust spots found in the darker tones.  
* Change the layer blend mode to darken, this restricts the edits to the lighter artifacts in the darker tones.
* Next apply a level or curve which slightly lightens the midtones - the more you lighten the less of an effect there will be. Due to the lightening edit, most of the filtering will be cancelled out - the result should be a reduction of the light spots in the darker tones.
* Dupe the background layer and apply slightly more filtering if needed than in the previous layer, to remove the darker spots found in lighter tonal areas.
* Change the layer blend mode to lighten, this restricts the edits to the darker artifacts in the lighter tones.
* Curve this layer so that it is slightly darker in the midtones, opposite to the edit in the previous layer. Due to the darkening curve, most of the filtering will be cancelled out - the result should be a reduction of the dark spots in the lighter tones.
* These corrections can be selectively layer masked into the original background layer to restrict the corrections to non critical image content, while critical areas of interest are hand spotted.

Both of the above dust/spot correction methods can be automated into a Photoshop action.

Software for removing grain/noise such as Neat Image, Noise Ninja or Grain Surgery etc may be of great help.

Don't forget to work on a duped, resampled down to the appropriate repro size to save work (unless you have to spot the original).

Also, as these are dark, perhaps some sort of K channel move might isolate them for blending or masking etc (max GCR or heavy GCR). Can blend if isolate the crud?

Can you post a hi res crop in the files section of this Yahoo group, of a small section showing both good and bad areas so that interested parties can experiment?

Best,

Stephen Marsh.
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Re: Eliminating Pepper Dots
    Posted by: "Greg Welch"
    Date: Wed Jun 21, 2006 6:27 am (PDT)

One other possibility is that the stabilizer and or last washes left a residue on the film. You could rewash film in dilute photo-flo solution. After film has been soaking for a few minutes gently and smoothly run the film between your fingers while wet then dip and hang to dry by one corner. Just a thought!

Greg Welch
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Re: Eliminating Pepper Dots
    Posted by: "leicamike2000"
    Date: Wed Jun 21, 2006 10:34 am (PDT)

George,
This worked great-thanks.I don`t understand why it worked but that`s ok.Thanks for all the replies.

Mike Sellers
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Re: Eliminating Pepper Dots
    Posted by: Stephen Marsh
    Date: Wed Jun 21, 2006 8:57 pm (PDT)

Mike, why not try to learn from the experience, read up on lighten and darken blending modes, consider the image content and what you are doing... there is a valuable opportunity for a quantum leap in your Photoshop work here... if only you would take those little extra steps to satisfy the curiosity, rather than just accepting that things work.

Time permitting of course.

Stephen Marsh.
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Fw: [colortheory] Re: Eliminating Pepper Dots
    Posted by: " fernchaves
    Date: Wed Jun 21, 2006 2:13 pm (PDT)

Hi,

I've read this article some time ago. It can probably help you:

http: //www.luminous-landscape.com/reviews/film/fuji-pepper.shtml

Best regards,

Fernando Chaves