Color Space for scans

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hhhhhhhh Regular Member • Posts: 170
Color Space for scans
1

Hi,

As a photographer, I always work in ProPhoto 16-bit and I print all my photos that way and they came out fantastic.

Now, as a painter, I gave my paintings to the studio to scan it and they returned it in a high resolution (tens of thousands of pixels on each side), but the color space wasn't assigned, and it was 8 bit TIFF.

I want to clean it up a little bit, before I return them for printing, but I'm curious, should I continue working on these files as they are, or should I convert them to 16bit and assign them some color profile? I won't change too much, they are good as they are, but I'll do a little clean up from dust and scratches. Maybe a bit of levels and curves, but just a touch. I don't want to spend days working on dozens of paintings, with the wrong settings.

I have to mention that 8 bit, without color profile is close to the TIFF limit of 4GB file size. Converting to 16 bit or assigning ProPhoto profile, I have to convert files to PSB.

Ken60 Senior Member • Posts: 2,228
Re: Color Space for scans

Firstly NEVER assign a profile.   Always convert TO a profile.  I can not see why you would want such a high pixel count file for printing , I would think it could become more of a hassle than an advantage.... unless of course your prints are going over a very large hoarding.

If you intention is to work with " normal " size A1 or A2 sized prints , I would convert to 16 bit and convert to colour space,  dust spot the images then make any adjustments before resizing to the print size at no more than 600 ppi . ..... or 720 for Epson .  Keep your Originals backed up somewhere safe , but use your newly converted files for repro.

The conversion from 8 bit to 16 is a bit of a lie and you might still have to watch how far you go with big changes to contrast .

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OP hhhhhhhh Regular Member • Posts: 170
Re: Color Space for scans

Ken60 wrote:

Firstly NEVER assign a profile. Always convert TO a profile. I can not see why you would want such a high pixel count file for printing , I would think it could become more of a hassle than an advantage.... unless of course your prints are going over a very large hoarding.

If you intention is to work with " normal " size A1 or A2 sized prints , I would convert to 16 bit and convert to colour space, dust spot the images then make any adjustments before resizing to the print size at no more than 600 ppi . ..... or 720 for Epson . Keep your Originals backed up somewhere safe , but use your newly converted files for repro.

The conversion from 8 bit to 16 is a bit of a lie and you might still have to watch how far you go with big changes to contrast .

Thanks for the reply.

Yeah, I realized later there is a difference between assign and convert, so I converted

The original painting is 11x14in and I plan to print it at 60in, so I want to make sure all dust, hair and micro scratches are removed, as they'll become apparent once enlarged 5 times.

After my original post, I converted it to ProPhoto, 16bit, to make sure I get the maximum quality. The file size is quite big - around 50gb, but I'm afraid to sacrifice the quality over the file size, because the storage is the least problem. Also, my computer can handle this file fairly well. I disabled PSB compression in Photoshop, so it opens within 10-12 seconds, and saves in around 15-20.

No problems at all with this file, except I'm used to work with photos of max 2-3GB (when I'm doing something complicated that requires lots of layers), so it feels heavy just looking at that number.

Also, I want to have the max quality, because I think this will be the last time I'll digitize my old paintings. Last time I did it 10 years ago, with the scanner I had at home and it cannot compare to this one. I probably won't need anything larger than this ever.

Ken60 Senior Member • Posts: 2,228
Re: Color Space for scans

You will need someone more versed in print than I am to give you the finer details of technology, but when ink hits paper , even coated stock , there is what is called dot gain .

Think fountain pen  ink on loo paper !  This will eventually diminish detail and the creation of a theoretical " perfect print" in dots. Add to that the spray ability of the inkjet and you might offer a certain resolution .... but never see it .  I print A2 in either 300 or 600 DPI , and I manage to convince myself that there is an improvement in the higher res. Beyond offering my Canon 12 cartridge A2 inkjet 600 DPI files , I fear it is a lost cause.Your 5 x increase in image size combined with the concepts mentioned above would make me think you are shouting at thunder above 300 DPI.   I would suggest 18,000 pixels along the long end is about fine for your usage. .... ( AKA 300 DPI)  and you could survive quite well at half that.

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OP hhhhhhhh Regular Member • Posts: 170
Re: Color Space for scans

I agree and I print all my photos in 300 or 600dpi on my home Epson P800 and can't see any difference.

But I got these scans in 2400dpi for 11x14in size, so I understand it should work perfectly for 60in in 600dpi, without losing quality.

technoid Senior Member • Posts: 2,276
Ask the studio what colorspace the scan is in
1

hhhhhhhh wrote:

Hi,

As a photographer, I always work in ProPhoto 16-bit and I print all my photos that way and they came out fantastic.

Now, as a painter, I gave my paintings to the studio to scan it and they returned it in a high resolution (tens of thousands of pixels on each side), but the color space wasn't assigned, and it was 8 bit TIFF.

A scan in RGB will be in some sort of colorspace most likely sRGB if untagged and not otherwise specified. But it could be something else. It might even be in native scanner RGB space like a raw desktop scan that hasn't internally been converted to something else like Adobe RGB. If the latter (in some sort of raw rgb) then the studio should have a profile you can first attach to the image from which you can then convert to a standard working space like ProPhoto. If the former then you need to find out from the studio which one and assign that colorspace to the image. Then you can convert it to whatever you desire assuming the gamut is sufficient.

NAwlins Contrarian Veteran Member • Posts: 5,181
Need to know to convert! Also ...
2

Firstly NEVER assign a profile. Always convert TO a profile. I can not see why you would want such a high pixel count file for printing , I would think it could become more of a hassle than an advantage.... unless of course your prints are going over a very large hoarding.

Yeah, I realized later there is a difference between assign and convert, so I converted

You cannot properly convert to a color space without first knowing (or having the scan file tell the software) what color space it's in to start with, that is, from what color space you're converting. 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.

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.

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.

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mike earussi Veteran Member • Posts: 8,711
Re: Ask the studio what colorspace the scan is in

8 bit can cause banding if you plan on doing any heavy manipulation. If I sent one of my images out to be scanned and was sent back a 8 bit file I'd be dissatisfied. If you payed for a high quality scan you should be getting a 16 bit tiff back.

Ken60 Senior Member • Posts: 2,228
Re: Color Space for scans

1) When you open your images in Adobe Photoshop, do you consider the colour ( as the original artist)  to be similar or the same as the original ?

2) When you look at your image on screen in Photoshop, go to the bottom left tool bar on screen where you can show file size/scratch size etc and scroll to image profile and what does it say ?

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technoid Senior Member • Posts: 2,276
Re: Need to know to convert! Also ...

NAwlins Contrarian wrote:

Firstly NEVER assign a profile. Always convert TO a profile. I can not see why you would want such a high pixel count file for printing , I would think it could become more of a hassle than an advantage.... unless of course your prints are going over a very large hoarding.

Yeah, I realized later there is a difference between assign and convert, so I converted

You cannot properly convert to a color space without first knowing (or having the scan file tell the software) what color space it's in to start with, that is, from what color space you're converting.

Exactly so.

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.

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.

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.

True for scans. Sensor noise is typically higher than 8 bit resolution with a reasonable gamma. At least for tiff files. Jpegs are more problematic as their lossy compression effectively reduces the resolution bits. Even so, jpegs are usually adequate.

A bigger issue with scans is metameric failure. That's a real issue as artwork can have quite diverse spectra. There really isn't much that can be done about that with normal commercial processes and it's rarely discussed outside of museum art archivists but is a real issue in precision reproduction work.

OP hhhhhhhh Regular Member • Posts: 170
Re: Color Space for scans
1

Ken60 wrote:

1) When you open your images in Adobe Photoshop, do you consider the colour ( as the original artist) to be similar or the same as the original ?

2) When you look at your image on screen in Photoshop, go to the bottom left tool bar on screen where you can show file size/scratch size etc and scroll to image profile and what does it say ?

1. It's very similar, in fact, looks perfect to me. I was just worried because it's 8-bit and if one day I want to do with it something more aggressive with the image and be limited.

2. Untagged RGB.

OP hhhhhhhh Regular Member • Posts: 170
Re: Need to know to convert! Also ...

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.

OP hhhhhhhh Regular Member • Posts: 170
Re: Ask the studio what colorspace the scan is in

mike earussi wrote:

8 bit can cause banding if you plan on doing any heavy manipulation. If I sent one of my images out to be scanned and was sent back a 8 bit file I'd be dissatisfied. If you payed for a high quality scan you should be getting a 16 bit tiff back.

I don't plan to, but I prefer having the max quality scans. I'm satisfied with the results and how it looks on my screen right now (didn't print it out yet), but still, number 8 bothers me

These guys are highly reputable studio specialized in fine art, and I guess they know what are doing. My paintings are almost monochromatic, so that might be one reason. Another reason is that I opted for flatbed option, which was 10x cheaper comparing to artwork capture with their 400mpx Hasselblad. So, I guess with artwork capture it will be 16-bit. Third reason might be that they tried to get the optimal file size for the print size I told them I'll be doing, because they sent me the files over the internet, so the speed might be the issue if they had to attach 50GB file.

technoid Senior Member • Posts: 2,276
Re: Need to know to convert! Also ...

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.

Well then if it's in sRGB that's actually a good fit for images that don't have colors outside of sRGB's gamut and it makes better use of the 8 bits than larger gamut colorspaces.

If your file is a tiff file, not jpeg, then you will not see any difference between 8 bits and 16 bits even when printed large. I've only very rarely seen an issue with jpegs which are effectively about 7 bits or less due to lossy compression. So doubt there is in issue even then. It is a good idea to convert to 16 bits prior to doing significant editing. You can induce artifacts with heavy editing of 8 bit files though it's often not an issue. You really have to work at it to see differences between 8/16 bits.

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 no such thing as an image in no color space. If an image is untagged it is usually displayed as if it was sRGB or whatever the default working space of the application is. Photoshop, for instance lets you set the default working colorspace which defaults to sRGB. Since your image is near monochrome sRGB is actually a good fit and it's likely the image was rendered in sRGB.

Mark McCormick Senior Member • Posts: 1,457
Re: Color Space for scans

If you are working on a properly color calibrated display and the untagged image color reproduction looks good to you in Photoshop, you are seeing the image being rendered by photoshop as if it is tagged with your photoshop default RGB working space color profile. Photoshop assumes untagged RGB images are encoded in Photoshop's RGB default working colorspace. In Photoshop, go to edit>color settings and see what the chosen default RGB working color space is set to. Typically, if you've never changed it from Adobe PS default setting, it's sRGB. Again, if the untagged image is rendering on your monitor with acceptable color accuracy (and your monitor is properly calibrated) then that is probably the color space the lab should have assigned/embedded during scanning, but regrettably failed to tag the file that was provided to you.

You can next use Edit>assign profile to embed this working space color tag so that it is saved during the next file save from photoshop. That fixes the issue of the file being in an "unknown" colorspace. You have essentially assigned it one you believe to be reasonably accurate in the absence of actually knowing what the lab really used when scanning the image. It's this very mystery meat untagged image file situation we are discussing that's a key reason Photoshop even has an "assign" rather than "convert" option in its color settings menu.

All that said, a pro lab offering pro level scans failing to provide the file with an embedded ICC profile is sooooo 20th century. No excuse for that sloppy technique nowadays. You should ask the lab to confirm the colorspace which they were using when they scanned the image and saved it. It could be a native scanner colorspace, if so, the scanner profile should have been embedded, but more than likely it was sRGB.

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Mark McCormick

OP hhhhhhhh Regular Member • Posts: 170
Re: Color Space for scans

Mark McCormick wrote:

If you are working on a properly color calibrated display and the untagged image color reproduction looks good to you in Photoshop, you are seeing the image being rendered by photoshop as if it is tagged with your photoshop default RGB working space color profile. Photoshop assumes untagged RGB images are encoded in Photoshop's RGB default working colorspace. In Photoshop, go to edit>color settings and see what the chosen default RGB working color space is set to. Typically, if you've never changed it from Adobe PS default setting, it's sRGB. Again, if the untagged image is rendering on your monitor with acceptable color accuracy (and your monitor is properly calibrated) then that is probably the color space the lab should have assigned/embedded during scanning, but regrettably failed to tag the file that was provided to you.

You can next use Edit>assign profile to embed this working space color tag so that it is saved during the next file save from photoshop. That fixes the issue of the file being in an "unknown" colorspace. You have essentially assigned it one you believe to be reasonably accurate in the absence of actually knowing what the lab really used when scanning the image. It's this very mystery meat untagged image file situation we are discussing that's a key reason Photoshop even has an "assign" rather than "convert" option in its color settings menu.

All that said, a pro lab offering pro level scans failing to provide the file with an embedded ICC profile is sooooo 20th century. No excuse for that sloppy technique nowadays. You should ask the lab to confirm the colorspace which they were using when they scanned the image and saved it. It could be a native scanner colorspace, if so, the scanner profile should have been embedded, but more than likely it was sRGB.

It is a properly calibrated monitor, but it looks good only because it has not much colors in it. If it's a photo portrait, I'd probably see the difference in skin tones, or if it's a landscape photo with lots of greens or blues. This is an abstract painting with lots of dark tones, blacks, grays and blues, so whatever color space I assign, it looks very, very similar and good to me.

I agree it's strange to provide files like this, especially for the lab known to work with well established artists and galleries. I also worked with them in the past, but I only printed my photos, never scanned before. I contacted them, but the guy who was actually scanning my photos was out for a day and he'll get back to me on Monday.

Until then, I'm working on my oversized files

Mark McCormick Senior Member • Posts: 1,457
Re: Color Space for scans
2

hhhhhhhh wrote:

It is a properly calibrated monitor, but it looks good only because it has not much colors in it.

Be aware that sRBG and aRGB color spaces have similar tone curves (not exact but close) with an approximately 2.2 gamma. ProPhotoRGB has a 1.8 gamma. Scanner profiles may be linear or something else.

Anyway, try this experiment, it will cost you only a few minutes of your time. Open the untagged file in Photoshop, and simply try assigning different colorspaces, e.g. sRGB, aRGB, proPhotoRGB using the Edit>assign profile menu in PS. As you switch between different assigned profiles, neutral will indeed stay neutral, but near neutrals and anything moderately saturated should shift in color. Also, switching from sRGB or aRGB to ProPhotoRGB should shift the mid tones and shadow values noticeably with respect to visual contrast even if hue and saturation isn't changing dramatically due to the low chroma nature of your image. Pick the colorspace that you think is closest to being correct in both color and tone reproduction. My guess is that it will be sRGB, but which ever one you like best is the one to permanently assign to the file in the absence of any proper guidance from your service provider.

cheers,
Mark

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Ken60 Senior Member • Posts: 2,228
Re: Color Space for scans

Great to see that as photoshop opens your file in its native space it looks good to you ..... just goes to show the difference between empirical theory and practical usage. As others have said it seems it may be sRGB 8 bit.

Luckily you have the original and the eye that created the artwork , so judging visually is most probably good enough. No shadow casts and a clean white with good contrast , you might have to play with your 16 bit file to get a printing file, obviously quite different from the screen file you like to see. Depending on the paper you select , the image will be flattened and require help to match the "look" of the screen image. It is at this point of playing with the tone curve , possibly darkening the low tones and lifting the midds, that you would encounter problems with an 8 bit file.

I had a friend that sold paintings in the USA and Germany ( mostly)  and before her paintings , pastels or screen prints  left I would capture them on a Sinar for all the catalogue and promotion work.   Going from Art, to film, to scanning, to 4 colour press, is a horror trying to get an exact replica..... But ultimately its an aesthetic judgement  that decides success.

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Ken60 Senior Member • Posts: 2,228
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.

Printing , especially to large dimensions  where all sins show, often requires exactly this manipulation of the tone curve more notably on art papers.

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Gear ... what I need to get the job done , after all you don't see mechanics listing their brand of spanner as a qualification .

Petruska Veteran Member • Posts: 8,932
What does your home Epson P800 print look like?

If good then you should be good at larger sizes from the lab...……..

Bob P.

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