Color Space for scans

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NAwlins Contrarian Veteran Member • Posts: 5,310
Re: Need to know to convert! Also ...

In a similar way, an 8-bit TIFF is every bit as good as a 16-bit TIFF for printing. The extra bits are only helpful if you will perform edits that substantially change the color and/or lightness.

In fact the fastest route to 8 bit banding is to play with the contrast curve and compress it . Try Ctrl + L in Photoshop and bring in the low and mid sliders a tad. Save and reopen your 8 bit file. Now look at the levels ( Ctrl + L) and note that it has changed from a curve to a bar chart.

Those are edits that (if done to a significant degree) substantially change the color and/or lightness. The OP made it sounds like the only editing was spotting or similar.

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Ken60 Senior Member • Posts: 2,305
Re: Need to know to convert! Also ...

NAwlins Contrarian wrote:

In a similar way, an 8-bit TIFF is every bit as good as a 16-bit TIFF for printing. The extra bits are only helpful if you will perform edits that substantially change the color and/or lightness.

In fact the fastest route to 8 bit banding is to play with the contrast curve and compress it . Try Ctrl + L in Photoshop and bring in the low and mid sliders a tad. Save and reopen your 8 bit file. Now look at the levels ( Ctrl + L) and note that it has changed from a curve to a bar chart.

Those are edits that (if done to a significant degree) substantially change the color and/or lightness. The OP made it sounds like the only editing was spotting or similar.

If you consider altering levels the way to change the colour of an image, then all I can ask is " Do you use Photoshop and do you have a copy for editing " ?   I have never heard of anyone using a Levels adjustment for colour changes !   Manipulating the tonal range of the curve is a very common adjustment for preparing a file for print..... if this was a colour changer no one would produce a good print.   You do produce large inkjet prints do you ?

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Mark McCormick Senior Member • Posts: 1,458
Re: Need to know to convert! Also ...
2

Ken60 wrote:

Manipulating the tonal range of the curve is a very common adjustment for preparing a file for print..... if this was a colour changer no one would produce a good print. You do produce large inkjet prints do you ?

Actually, when working with RGB tone curves the chroma and to a lesser extent hue values do change as you increase or decrease the RGB tone curve(s). So, for example, when increasing the tonal contrast the image tends to saturate more as well, but many folks welcome that extra "pop" and think of it as part of the increase in visual contrast.

That said, Photoshop does offer a way to edit RGB curves while keeping the color values (hue and chroma) the same. In the curves dialog window, just change the the curve adjustment layer's setting from "normal" to "luminosity" mode. That tells PS to adjust the RGB numbers using a color managed shift in the RGB numbers such that the profile referenced L* values guide the RGB numeric changes while keeping a* and b* (hue and chroma content) constant. This approach can be very useful, for example, when skin tones are being rendered and you want to raise or lower the overall contrast of the scene without changing the current color appearance of the skin tones if they already appear to have pleasing color values.

cheers,
Mark

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NAwlins Contrarian Veteran Member • Posts: 5,310
Re: Need to know to convert! Also ...
1

In a similar way, an 8-bit TIFF is every bit as good as a 16-bit TIFF for printing. The extra bits are only helpful if you will perform edits that substantially change the color and/or lightness.

In fact the fastest route to 8 bit banding is to play with the contrast curve and compress it . Try Ctrl + L in Photoshop and bring in the low and mid sliders a tad. Save and reopen your 8 bit file. Now look at the levels ( Ctrl + L) and note that it has changed from a curve to a bar chart.

Those are edits that (if done to a significant degree) substantially change the color and/or lightness. The OP made it sounds like the only editing was spotting or similar.

If you consider altering levels the way to change the colour of an image, then all I can ask is " Do you use Photoshop and do you have a copy for editing " ? I have never heard of anyone using a Levels adjustment for colour changes ! Manipulating the tonal range of the curve is a very common adjustment for preparing a file for print..... if this was a colour changer no one would produce a good print. You do produce large inkjet prints do you ?

Since you've gotten rather snippy, I'll suggest: check your reading comprehension, regarding my earlier post quoted above: "if you will perform edits that substantially change the color and/or lightness." (Emphasis added.) Now, using levels or a unified curve to an appreciable extent will substantially change the lightness; using separately the R, G, and B curves to an appreciable extent will substantially change the color. If you do either of those with an 8-bit file, you may introduce visible banding or the like.

With that established, let's go back to the what OP is doing: it sounded to me like only spotting / dust cleanup / that sort of thing, i.e., not making global (or even sizeable-area local) adjustments to the color and/or lightness. It really doesn't matter what others commonly do, unless the OP is doing it.

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Ken60 Senior Member • Posts: 2,305
Re: Need to know to convert! Also ...

Sorry Nawlins to offer any more comment to clear up your misunderstanding, I need you to tell me the version of Photoshop you use to print with at home . ...,.,. I note you answered neither of my queries.

Once I know which version you are using I can post captures to aid your following.

I look forward to your reply to those questions.

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NAwlins Contrarian Veteran Member • Posts: 5,310
No misunderstanding on my part
1

Sorry Nawlins to offer any more comment to clear up your misunderstanding, I need you to tell me the version of Photoshop you use to print with at home . ...,.,. I note you answered neither of my queries.

Once I know which version you are using I can post captures to aid your following.

I look forward to your reply to those questions.

Okay, to orient and clarify: I am not the OP, I don't have a question, and I'm not misunderstanding anything. I am (was? we seem to have gotten sidetracked) here to try to help the OP. My response to the OP appears at https://www.dpreview.com/forums/post/64236744, and it was mainly about converting from one color space to another.

You disagreed with my comment about whether the OP working with 8-bit TIFFs is a problem. Although I agree that working with 8-bit files can be a problem, I think that based on what the OP claims to be doing to the 8-bit TIFFs at issue, it probably won't be a problem.

FWIW, since you seem set on finding out what software I use to print at home, recently I've switched from generally printing with Lightroom to generally printing with Qimage.

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Ken60 Senior Member • Posts: 2,305
Re: Need to know to convert! Also ...

Thats a lot of words to hide the fact that as per usual, the guy that does not use Photoshop ( other than an old copy of Elements) is trying to offer me advice on how to use Photoshop. Unbeknown to you I  have used the software professionally since version 2 , and taught college students to use it.  Add to this the same guy that prints max 8"  wide at home spends time contradicting posts by users of machines he has never owned,  or used.

My best advice to you is to try and refrain from comments in areas where you have no active  participation , and stick to the things you use and know.  Passing along information from LULA and reading other peoples advice on forums only goes as second hand information.

When you pull an area of a curve in Photoshop "upwards, the only part of the image that is lightened is that where the curve is lifted. In Photoshop you can offer the curves layer adjustment from the bottom of the layers toolbox ..... here select the hand pointer and in the image go to a mid tone and whilst clicking and dragging on the screen image you will lift the mid tones related in the curve.  Now some of the image might be a tad lighter , however the numeric values for lightness and colour in both the shadows and the highlights will be the same.    The "image " as a whole is NOT lightened , only a select part is.  If as some suggest that the entire colour balance of the image is poisoned , or the global image is lightened , then Adobe would never have become the global leader in image manipulation.

Now we have cleared this up perhaps you can pop off to the medium format area and offer advice to the users of high end digital medium format cameras , not that you own or use one of these either.

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NAwlins Contrarian Veteran Member • Posts: 5,310
[EDITED] Completely misdirected?
1

Ken60 wrote:

Thats a lot of words to hide the fact that as per usual, the guy that does not use Photoshop ( other than an old copy of Elements) is trying to offer me advice on how to use Photoshop.

No, I'm not trying to offer you, Ken60, advice on how to do anything! I wonder whether possibly you have me confused with someone else, or you've misread this thread. The OP here is hhhhhhhh, not Ken60, and hhhhhhhh is the person to whom my suggestions are mainly directed.

I thought you and I have what I still think is a minor disagreement about the significance or lack thereof to hhhhhhh working with artwork scans that are 8-bit TIFFs instead of 16-bit files, given the edits that the OP is performing (and in light of the the complication that the OP raised, that these 8-bit TIFFs are already close to the format's 4 GB limit, meaning there could not be a full-resolution 16-bit TIFF, which would mean that to use 16 bits, the files would have to be PSBs). I think that if the OP is basically only spotting the scans, which is what I thought the OP had indicated, then 8 bits is okay.

Beyond that, if you can quote something I've posted that is substantively wrong (and not merely contrary to your opinion), then by all means please do so because sometimes I'm wrong and I like to learn. But please don't misrepresent or assume what I've written or think. The rest of your post certainly attributes to me things I did not write.

[EDIT]

I went back and re-read the posts, to see whether I missed something. In the very first post, the OP wrote:

I'll do a little clean up from dust and scratches. Maybe a bit of levels and curves, but just a touch.

So in fairness I glossed over the "[m]aybe a bit of levels and curves" more than I should have. For cleaning up dust and scratches, starting with an 8-bit TIFF should not be a substantial issue. For levels and curves--if the OP actually does what's presented as a maybe--whether starting with an 8-bit TIFF is a significant problem depends on what the OP means by "a bit". To me, that means a very subtle change, and that sort of very subtle change is unlikely to induce visible banding. But in fairness, I've seen people make changes to things that they'd called 'a bit' of a change or similar, that I thought were more substantial.

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pixelgenius
pixelgenius Senior Member • Posts: 4,228
Re: Color Space for scans
1

Ideally you want the scans in the scanner color space, 16-bit. Any decent scanning software should have a profile for that scanner and embed it from that color space.

If you got an untagged document, that's bad! You need to know it's color space and assign it to that untagged data.

pixelgenius
pixelgenius Senior Member • Posts: 4,228
Re: Need to know to convert! Also ...
2

hhhhhhhh wrote:

IMO the must-do item is to ask the service that scans your art what color space they're saving it it. If they aren't aware of color spaces, then IMO look for a new service.

Also good advice. There is a slim chance it's in the native camera/scanner colorspace. Sort of like one of the options dcraw.c has for raw images. But you then need an input profile attached to it so it can be converted to a standard colorspace. So I suspect it's already converted to some standard colorspace. Odd that they haven't tagged it so it may be just sRGB which is not adequate for scanning artwork that has highly saturated colors. Depends on the artwork.

Actually, my paintings are very desaturated, almost monochromatic. But still, even if it's B&W, I'd prefer 16, over 8-bit.

Assuming that they are saving it in a color space that the service that prints it can use, I see no reason to convert to a different color space unless you're performing edits that will substantially change the color. If they scan to sRGB and that clips your art's colors, then your converting from sRGB to e.g. ProPhoto RGB is not going to restore those colors.

Yep.

I see no color space assigned to the files. It says "Untagged RGB", which I assume it's no color space at all.

There is always a color space, assumed or otherwise. So in this case, it's assumed even though you're told 'Untagged RGB" . Photoshop will use whatever RGB Working Space is selected in Color Settings as the assumption for untagged data (RGB Working Space). That assumption may be wrong hence the reason Assign Profile command exists.

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