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Color Space Choices for Nikon 5000 Scans

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  #1  
Old 07-23-2010, 10:25 PM
stlsailor stlsailor is offline
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Color Space Choices for Nikon 5000 Scans

Using Nikon Scan 4 on a Super Coolscan 5000, and assuming 16-bit scanning, there are several color space choices. The most likely choices seem to be Adobe RGB, Wide Gamut RGB, and Wide Gamut RGB (Compensated).

I'd think there are three objectives:

(1) Scan for archival purposes in a color space that most closely approximates the colors that the scanner can capture from the positive or negative.
(2) Work in a color space that is designed for neutral grays.
(3) Capture in a color space that is likely to be supported well into the future.

Beyond family record photos for which sRGB would probably be sufficient, it seems the most likely choices for color space for scanning and corresponding working space in PS CS5 are:

(1) Scan in Adobe RGB; work in PS in Adobe RGB. You have consistency and aRGB is good enough for many commercial processes.

(2) Scan in Wide Gamut or Wide Gamut (compensated); work in PS in Wide Gamut. It is not clear how Wide Gamut (compensated) maps to Wide Gamut in PS or how quickly Wide Gamut will be completely displaced by ProPhoto RGB.

(3) Scan in Wide Gamut or Wide Gamut (compensated), work in PS in ProPhoto RGB.

I am not actually yet convinced that any color space larger than aRGB is a necessity, but I've got several thousand photos to scan and don't want to have to redo it later, and will probably work in ProPhoto for DSLR RAW images, so I'd probably just scan in that if I could.


Dale
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Old 07-25-2010, 11:10 PM
stlsailor stlsailor is offline
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Re: Color Space Choices for Nikon 5000 Scans

An additional note:

I scanned a group of images four times -- (1) sRGB 8 bit, (2) Adobe RGB 8-bit, (3) Adobe RGB 16-bit, and (4) Wide Gamut compensated 16-bit. I viewed the images on a calibrated monitor.


STEP ONE: I looked at the histogram on all the scans.

aRGB-16 gave the widest range. sRGB-8 and aRGB-8 gave slightly narrower ranges. WGc/16 gave the narrowest range.


STEP TWO: I opened all four images in PS CS5, created a Curves layer, and hit the auto button.

The histogram for WGC-16 had banding in the extreme left side of the histogram. For aRGB-16 it had no banding in the histogram. The two 8-bit images had banding as expected.

aRGB-16 had the most accurate color based on the original transparency, followed closely by aRGB-8, though both were slightly oversaturated. WGC-16 were undersaturated. sRGB-8 was consistently worse.

WGc-16 had the most visible shadow detail without enlarging. However it also had significant noise in the underexposed shadow area whereas aRGB-16 and aRGB-8 had virtually no noise. I do not understand why the color space choice would affect noise.

The differences were very significant where color fading had occurred; otherwise they were much less significant.


STEP THREE: I scanned several of the transparencies at 16-bit with scanner RGB and created duplicates. I PS CS5 I assigned aRGB to one; WGc to the other. Again I hit the auto button on curves and the aRGB had significantly more accurate color.

My conclusion at this point is that with several thousand slides to scan, the least work to get the most accurate color would be to scan 16-bit using Adobe RGB.

Dale
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Old 07-26-2010, 08:45 AM
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Re: Color Space Choices for Nikon 5000 Scans

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Originally Posted by stlsailor View Post
(1) Scan for archival purposes in a color space that most closely approximates the colors that the scanner can capture from the positive or negative.
Then you’d want to scan into “scanner RGB”, its native color space, described by an input profile of that device. No such option in the software you’re using?

I can tell you that you absolutely want to scan high bit (16-bit although its unlikely that’s the bit depth of the scanner). And you want a working space if that’s the only option that’s wider than sRGB and probably Adobe RGB (1998). Its quite likely the scanner’s native color space is much larger than either of those two working spaces. Again, the native space is the “purest” capture of data at this stage. At some point, you’ll likely want to convert it into a working space for editing.
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Old 07-26-2010, 09:13 AM
stlsailor stlsailor is offline
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Re: Color Space Choices for Nikon 5000 Scans

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Then you’d want to scan into “scanner RGB”, its native color space, described by an input profile of that device. No such option in the software you’re using?
That is what I would have thought. However I'm thinking that's not true for two reasons. First, the Nikon Scan 4 manual says ""This profile replicates the color space achieved when scanning with Nikon CMS off. Its main purpose is to allow the LCH editor and Unsharp Mask tools, which are not available when Nikon CMS is off, to be used to edit the colors produced by the scanner. In order to produce the effect achieved by turning Nikon CMS off, the monitor profile is not used, nor is an ICC profile included with the image when it is opened in the host application." The second reason is that when I scanned in Scanner RGB and assigned either ProPhoto or Adobe RGB as the color space, the results were not nearly as good as scanning directly into Adobe RGB.

Quote:
I can tell you that you absolutely want to scan high bit (16-bit although its unlikely that’s the bit depth of the scanner).
Yes, after looking at the sample scans I'd have to agree. In some cases the 8-bit is almost as good as the 16-bit, but in other cases it's not. In any case the histogram makes the data loss fairly clear.

Quote:
And you want a working space if that’s the only option that’s wider than sRGB and probably Adobe RGB (1998). Its quite likely the scanner’s native color space is much larger than either of those two working spaces. Again, the native space is the “purest” capture of data at this stage. At some point, you’ll likely want to convert it into a working space for editing.
sRGB was consistently the worst of all my sample scans, so I've ruled that out. I would have expected Wide Gamut or Wide Gamut compensated to have produce better results, but Adobe RGB seemed to. I thought, too, and still do, that the scanner's native color space is wider than Adobe RGB, but that is based on no evidence. I haven't been able to find an explicit comparison.

I went into this expecting that Wide Gamut compensated would produce the best results. So far Adobe RGB seems to, which was a surprise. It may be with extensive editing that I can get more out of Wide Gamut, but with several thousand slides there's not time for extensive editing.

Dale
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Old 07-26-2010, 09:19 AM
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Re: Color Space Choices for Nikon 5000 Scans

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Originally Posted by stlsailor View Post
The second reason is that when I scanned in Scanner RGB and assigned either ProPhoto or Adobe RGB as the color space, the results were not nearly as good as scanning directly into Adobe RGB.
You’d never do that. You’d assign the scanner profile. Ideally, the software would embed this. Ideally you’d build your own scanner profile too. Part of the issue may be the scanner driver (Nikon kind of sucks when it comes to color management). Assuming you don’t want to switch, might be best to use either Adobe RGB (1998) or maybe ProPhoto RGB which I know is vastly larger than the scanner native color space. The alternative is to find a driver that has a better COLOR MANAGEMENT idea of a workflow, something like SilverFast.
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Old 07-26-2010, 12:28 PM
stlsailor stlsailor is offline
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Re: Color Space Choices for Nikon 5000 Scans

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You’d never do that. <scan in scanner RGB and assign a color space in PS> You’d assign the scanner profile. Ideally, the software would embed this.
I tested it because on some forums it has been suggested. My results bear out what you're saying. It's not a good approach. It doesn't appear that NS4 embeds a scanner profile, though. So this option is off the table.

Quote:
Ideally you’d build your own scanner profile too. Part of the issue may be the scanner driver (Nikon kind of sucks when it comes to color management). Assuming you don’t want to switch, might be best to use either Adobe RGB (1998) or maybe ProPhoto RGB which I know is vastly larger than the scanner native color space. The alternative is to find a driver that has a better COLOR MANAGEMENT idea of a workflow, something like SilverFast.
I'm not ruling out VueScan or SilverFast. Some people who use them seem to like them. Others don't like them much at all. I'm willing to spend the money if I see a clear benefit. Vuescan doesn't seem to differentiate between Kodachromes and other positives in their ICE selections which NS4 does. I haven't been able to find a list of what color spaces it supports. Silverfast seems overly expensive.

Adobe RGB (1998) seems to produce better color than Wide Gamut compensated (which is probably NS4's closest equivalent to ProPhotoRGB). I'm not sure why. I haven't yet tried converting either one to ProPhotoRGB, but since at least Adobe RGB is a narrower color space, I don't know that there's any benefit to testing it other than for Wide Gamut.

Dale
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Old 07-26-2010, 01:09 PM
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TommyO TommyO is offline
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Re: Color Space Choices for Nikon 5000 Scans

Stlsailor,
It sounds like you have a good feel for what you're doing and a good working knowledge of color management. So, my 2cents would be.... I tend to look at past experiences to guide me on projects like this. When scanning large numbers of images simply for archival, I like to keep it somewhat simple. Scan at a reasonably high bit depth and in a large well supported color space. I know it's not likely I will ever access or edit very many of these images. But, I may chose to run some type of batch process on them 10-20 years from now and would prefer it run without any hiccups. At that point in time, who knows what technology will be available, but I'm confident it will be far superior to todays. Bit depth and color spaces from this era will be considered ancient if not irrelevant. If I were going to be editing these images in the next few years, I would be more concerned about the specifics. I often break out certain images I want to retouch soon and scan them differently, in effect doing two batches, one for archival one for retouch.

I would agree that the Wide Gamut color spaces are likely a Nikon creation and would avoid scanning in that space. Is ProPhoto RGB too broad?... not likely. In fact, Adobe engineers (whom have an excellent reputation) decided to use that as the working color space within Adobe Camera Raw. ACR works in ProPhoto RGB with a linear gamma prior to saving in your color space of choice.

So, I guess what I'm saying is... for archival, keep it simple, keep it accurate, keep it standardized. Focus more on your archival workflow so that all those scans will still be intact 20 years from now. Do a separate scan for any images you may choose to edit and print in the near future.
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Old 07-26-2010, 10:45 PM
stlsailor stlsailor is offline
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Re: Color Space Choices for Nikon 5000 Scans

TommyO,

I appreciate your thoughts, especially the philosophy of keeping it simple when you've got a big workload. I'm open ears.

I hadn't thought of differentiating archival from current images in the way you suggest. It makes sense. Given that, here's what I'm seeing as a high level archival workflow omitting metadata and cataloging considerations for simplicity.

1- Standard archival scan at 2400 dpi 16-bit in Nikon Adobe RGB with only Digital ICE creating TIFF_TEMP.

2- Open in PS, convert color space to standard Adobe RGB, then save as archival image TIFF_ARCHIVE for later offline storage. The temporary image in the above step is no longer needed.

3- Do basic editing in PS as needed (capture sharpen, tonal, color, noise), but don't do intensive editing now. Save the layered TIFF as the new TIFF_MASTER.

4- Pick/Reject/Rate in LR3. Delete rejects. Put an image on a list to rescan with different parameters (e.g. 4000 dpi) if
  • it is going to be worked on any time soon
  • is a high star rated image with intrinsic value beyond being simply a family snapshot
  • is likely at some point be enlarged greater than 8 x 10
  • will have a small portion cropped and enlarged.
A few thoughts.

Most scanned images appear to need some PS work, even if only auto. That's why I haven't put a Lightroom step in the workflow.

Always scanning at 16-bit simplifies the workflow and considers your comments about the future. (A friend cautioned me, though, whatever we do today will look quaint in the future just like old images do today, so don't cause myself too much work.)

I expect to use ProPhoto RGB for DSLR RAW (I recently upgraded to PS CS5). But scanning in Wide Gamut and converting to ProPhoto didn't seem to capture color as accurately and simply as Adobe RGB. Nikon Adobe RGB (1998) is almost identical to Adobe RGB (1998) based on the histograms, but perhaps standardization is still worth the conversion step. Perhaps I could automate it in PS?

I'm also considering whether to leave the master image in TIFF format or convert to PSD (or to DNG but I haven't seen a reason for that)?

I'd rather do the scans (steps 1-2) independently of steps 3-4. But until I've done basic tonal corrections and color restoration I don't know if they are picks or not, or if I want to rescan them with different parameters. I guess I still could do the two functions as independent workflows though.

Given that as the strawman, does that accurately capture your thoughts on color space and bit depth, or is there something you'd suggest considering changing?

Dale
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Old 07-27-2010, 12:18 AM
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Re: Color Space Choices for Nikon 5000 Scans

Stlsailor,

I like the fact that the workflow is defined, and that it is fairly strait-forward. I'm in agreement that you should focus on steps 1 & 2 independent of 3 & 4.

And, of course, some other modifications could depend on how many scans we're talking about. You can add up the time spent per image and let that influence the workflow as well, versus what you really want to spend per image. I like the workflow for small numbers of scans, but think it could be lengthy for large numbers.

For example, step 2: if doing a large number of scans, I wonder if step 2 should only be performed if it can be run as a batch command.

Also, step 3: I know you mentioned this would allow you to make some decisions about the image. However, if it cannot be automated with a script, it could also be quite time consuming. Hence, possibly you may have to use your eyes during step 4 to make some judgments. (It doesn't take many scans before the brain works better than Photoshop in predetermining what can be done with an image.)

I would look at standardizing on AdobeRGB if you can automate it, as you suggested.

I'm on the fence regarding TIFF, PSD or DNG. I'm thinking PSD, until at some point in the future it is not supported (not likely). At that time run a batch conversion to the latest format. We could see newer versions of PSD require some conversion of older versions; again a major batch convert and your done.

Again, it boils down to the quantity. The times I have scanned 100's of images, I've been glad I simplified the workflow. I have not gone back to very many of those to edit... maybe 2 per 100 at the most. The rest just sit there for safe keeping. It's easy to see that if I ever wanted to restore one today, I'm confident today's software could do a much better job than what I had 7 years ago. So, looking ahead, I can't imagine your regretting not doing more restoration of them now. Ten years from now it may be you can batch restore nearly all of them with one click.

Hopefully, Andrew or others will chime in and give their thoughts as well. Otherwise, best of luck and let us know your final thoughts.
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Old 07-27-2010, 11:54 AM
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Re: Color Space Choices for Nikon 5000 Scans

Quote:
Originally Posted by stlsailor View Post
I expect to use ProPhoto RGB for DSLR RAW (I recently upgraded to PS CS5). But scanning in Wide Gamut and converting to ProPhoto didn't seem to capture color as accurately and simply as Adobe RGB. Nikon Adobe RGB (1998) is almost identical to Adobe RGB (1998) based on the histograms, but perhaps standardization is still worth the conversion step. Perhaps I could automate it in PS?
Its pointless to go “Wide Gamut” (not sure what that is) to ProPhoto RGB. I’m assuming Wide Gamut is an RGB working space like ProPhoto but with different primaries defining it and hence its gamut. Again, the best archival approach would be to scan and tag in the native color space of the scanner. Its not too large or too small, it IS what the scanner is producing. Then, tomorrow or in 20 years, you can convert to a working space. Keep color conversions to a minimum. There’s really no conversion when you scan into the space of the scanner at this point.
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