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Old photo restoration - Bridge or Photoshop, RGB or Grayscale?

Enthusiast ,
Aug 10, 2019 Aug 10, 2019

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Hi guys,

I Have an old photo and I scanned it in 200% and 600 ppi, saved as Tiff.

Got a few questions I always wondered about:

1. I was wondering, if I want it to be Black/White, where is it best to do. Bridge or Photoshop?

2. Is it better first to change it to Black/White and then retouching, or the opposite?

3. What is best: Black/white Grayscale or RGB? Or shall I first do the Gray scale and than back to RGB?

Thank you very much

Shlomit

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correct answers 1 Correct answer

Community Expert , Aug 11, 2019 Aug 11, 2019

Without seeing an example it's impossible to give specific advice. But generally you will have more flexibility working in RGB. Don't throw away information before you have to.

I'd also avoid grayscale as an output from Photoshop for other reasons. Grayscale is subject to standard color management, and it makes a huge difference what grayscale profile is used. This is all correctly handled inside Photoshop - but grayscale support outside Photoshop is mostly non-existent, and the final result ther

...

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Community Expert ,
Aug 11, 2019 Aug 11, 2019

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Without seeing an example it's impossible to give specific advice. But generally you will have more flexibility working in RGB. Don't throw away information before you have to.

I'd also avoid grayscale as an output from Photoshop for other reasons. Grayscale is subject to standard color management, and it makes a huge difference what grayscale profile is used. This is all correctly handled inside Photoshop - but grayscale support outside Photoshop is mostly non-existent, and the final result therefore totally unpredictable.

Grayscale data very often don't have an embedded icc profile to determine the tone response curve. Inside Photoshop that means the working gray gets assigned. The Photoshop default working gray is a dot gain profile with little practical relevance. You're much safer changing your working gray to Gray Gamma 2.2, which roughly corresponds to Adobe RGB, or sGray, which corresponds to sRGB.

The problem is that other applications mostly don't know what to do with Gray Gamma 2.2, or sGray. So that profile usually gets thrown out, and the data just treated randomly. An RGB file with sRGB or Adobe RGB embedded has a much higher chance of being correctly treated.

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Community Expert ,
Aug 11, 2019 Aug 11, 2019

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You don't mention whether the photograph is a color print or vintage black & white, or sepia image. Assuming it is a color photograph, Photoshop's Mode > Grayscale is not recommended.

To quote from Dan Margulis'* "Professional Photoshop", when referring to Mode > Grayscale "... no matter what color space the file is currently in, Photoshop creates an idealized version of it, and from that a weighted average to make a single channel. The formula is 3-6-1, three parts red, six parts green , one part blue." Margulis goes on to demonstrate why this formula "doesn't work."

Depending upon the actual image, adjacent colors and their intensity, you may find that Image > Adjustments > Black & White presents useful starting options. In addition, if the image displays scratches, dust specks, lack of image sharpness and other distractions, there are several tools available to deal with them. If you run into a problem, post the image and ask for help.

*Margulis is more widely known for his groundbreaking books related to Lab Color.

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Community Expert ,
Aug 11, 2019 Aug 11, 2019

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As mention above rgb is best even for grayscale. You can often enhance a particular channel in rgb to give better contrast and detail, even if you want a grayscale image.

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Community Expert ,
Aug 11, 2019 Aug 11, 2019

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norman.sanders  wrote


a weighted average to make a single channel. The formula is 3-6-1, three parts red, six parts green , one part blue.

I don't believe there is such a formula. That notion probably stems from the fact that a bright yellow remains bright in grayscale, instead of turning muddy gray as it would be with averaged RGB.

The grayscale image is not derived from RGB, but from a modified Lab L version. They're not identical, but exactly what that modification is nobody knows. We've had numerous discussions about that, with no conclusion. In Photoshop it's just known as "luminosity", a term not used anywhere else to my knowledge, and which is probably proprietary.

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Community Expert ,
Aug 12, 2019 Aug 12, 2019

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https://forums.adobe.com/people/D+Fosse  wrote

norman.sanders   wrote

To quote from Dan Margulis'* "Professional Photoshop", when referring to Mode > Grayscale "... no matter what color space the file is currently in, Photoshop creates an idealized version of it, and from that a weighted average to make a single channel. The formula is 3-6-1, three parts red, six parts green , one part blue.

I don't believe there is such a formula.

I'd believe Dan Margulis on that, and in addition, that 3-6-1 formula is corroborated on pages 17 and 31 in a document by Jeff Schewe (In Search of the Perfect B&W Print), linked from the answer to an Adobe Forums discussion from 2015 (Mode > Convert > Greyscale RGB %s). I'd believe Jeff too.

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Community Expert ,
Aug 12, 2019 Aug 12, 2019

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I make it a point of principle to never trust authorities   They are sometimes wrong too.

But that's not why I doubted it. It's more that it a priori seems needlessly convoluted and complicated - and arbitrary: why that ratio and not another?

It seems infinitely much simpler to just take the Lab L channel, and get the same result. After all, Lab is a profile connection space (with CIE XYZ) and Lab is always in the background in Photoshop. The numbers are readily available without any extra calculation.

The point of the whole exercise, by whatever method, is to retain the inherent brightness of individual colors. Average out a bright yellow, R+G+B/3, and you get middle gray. You don't want that. Lab keeps the brightness because the luminance component is separate.

Anyway, I'll make a few tests one day when I have time.

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Community Expert ,
Aug 12, 2019 Aug 12, 2019

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D Fosse your comment about needlessly convoluted and complicated made me chuckle. I've took a black and white conversion class with a very well known instructor. His methods were so convoluted and complicated! The whole time I was in the class, I kept thinking, why doesn't he just do it like this and be done with it? The results IMO were mostly subjective anyway.

With the OP's image, since it's already monochrome, just looking at the channels will give a good idea on which one(s) to use. Obviously the red channel will have little contrast.

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Community Expert ,
Aug 12, 2019 Aug 12, 2019

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https://forums.adobe.com/people/Chuck+Uebele  wrote

just do it like this and be done with it

My philosophy exactly You can't go wrong...

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Community Expert ,
Aug 11, 2019 Aug 11, 2019

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Save it as a PSD (and what the others state).

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Enthusiast ,
Aug 11, 2019 Aug 11, 2019

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Dear All,

Thank you so much for your advices. Here is the photo I want to work on.

Although I'm not familiar with all the deep Photoshop options, I get help from tutorials and all your advices will help me on that.

I wish you all a very good day...

Shlomit

Childhood0001-Step01sw.jpg

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Community Expert ,
Aug 12, 2019 Aug 12, 2019

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Here is the photo I want to work on.

You haven't mentioned what the intended output will be—composite color printer or offset printing? Your scan obviously has color in it, are you trying to convert the original scan color so that the output is perfectly neutral, or are you trying to reproduce the original color? If the output is offset and you are looking for neutrality, RGB mode will convert to 4-color CMYK, while Grayscale mode will output to the black plate with no CMY.

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Community Expert ,
Aug 12, 2019 Aug 12, 2019

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https://forums.adobe.com/people/rob+day  wrote

Grayscale mode will output to the black plate with no CMY.

Yes, and that's a perfect example of the problems you can get with grayscale. You get the CMYK profile's black ink assigned to the data - but that's not the profile used when creating the file. So the tone response curve comes out all wrong.

Unless you're prepared for that, and set your working gray up accordingly, so that you can assign that to the file and work with that:

black_ink_1.png

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Community Expert ,
Aug 12, 2019 Aug 12, 2019

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It looks to me like the OP wants to reproduce the color original, but the grayscale question makes that a bit ambiguous.

The reason I brought up the print destination is, RGB might have its own set of problems in offset output. As you point out, with a composite printer like inkjet, there would be no point in converting to grayscale because the printer very likely will have an RGB driver with an RGB output profile as the final destination.

If the output is offset, and you leave the neutral color as RGB in the layout, it will get converted to 4-color on export or print. Unless the press is running exactly to the document’s assigned profile with perfect gray balance, there will likely be some kind of color cast on press.

If the goal is maintaining neutrality one could do a custom CMYK conversion with heavy or maximum black generation, which would lower the relative amount of CMY and do a better job maintaining neutrality on press. Or, the output could be grayscale, which obviously has no color cast problem, but may not have as much dynamic range (the shadows would have no CMY boost).

InDesign, for good reason, has no grayscale space, and uses the document’s assigned CMYK black ink profile for the grayscale preview when Overprint is turned on. So if the destination is offset, and you want black plate only output, the ideal would be to use a matching Black Ink Gray profile in Photoshop, and not a legacy curve based dot gain or gamma profile, which will likely change the grayscale’s appearance in the layout.

If you want to control tonality of the color conversion into grayscale, it would just be a matter of using a Black & White layer on the RGB document (or some other preferred technique), followed by a Convert to Profile with the Black Ink profile as the destination grayscale. In that case the intended tonality wouldn’t change on the Photoshop conversion, or over in the page layout.

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