VueScan/Color management question

[whitestone]

I purchased VueScan and used it to profile my scanner and the output looks

great. Just for kicks, I decided to try to do manually what VueScan is doing

with the color spaces. I made a raw scan (Media set to Image, Color Balance set

to None, and Output color space set to ScannerRGB). I took the resultant Tiff

file, which had no embedded profile, and loaded it into PS. I then assigned the

scanner profile (the icc file made by VueScan) and then converted to AdobeRGB,

and the result looks completely different from what I get directly from VueScan

when VueScan is using the scanner profile. I must be missing some fundamental

concept. I thought I could take a raw scan, assign the scanner profile, and then

convert to AdobeRGB. But it doesn't work for me. Or maybe I don't know how to

make a raw scan file. Any suggestions?

[roger_smith4]

Vuescan deals with profiles differently than Adobe. If you use VS to profile the scanner and then assign it in Photoshop results should be identical. If you use a more sophisticated program to create the profile and then assign in in VS and Photoshop, results are different. Because of this I stopped assinging profiles in Vuescan, and instead output in "device RGB" and assign in Photoshop.

 

There's no real need to scan in linear raw but with slides I do suggest scanning with color balance "none" and output space "device RGB" and let Photoshop do the rest. I recommend the free program Scarse for profile creation- once you figure out the command line interface it works great and you can create custom profiles for different scanner exposure settings.

[davem1]

I also experimented with VS and PS assigning profiles.

 

I made my profile using Profile Maker Pro and I let Vuescan assign it.

 

I also find that it offers more of an accurate color match to the slide than assigning it in PS...

[Tim_Lookingbill]

Great, I guess all this CM technology still remains a tower of

color Babel.

 

So when you open the already assigned correct looking in

Vuescan image in PS, you still have to edit it to get it back to how

it looked in Vuescan? Or is it the assigning process in which

image program chosen that changes the preview?

 

So much for setting up automated workflows.

[peter_langfelder]

Vuescan appears to do some internal color processing when it outputs regular tiff/jpg output. The processing is not done on raw files, of course. I complained about this several times, to no avail. I guess it's Vuescan's "interpretation" of what the scanner (with a profile or without) sends it.

[william_john_smith1]

Did you try it using Vuescan's "Raw DNG" format?

[roger_smith4]

"So when you open the already assigned correct looking in Vuescan image in PS, you still have to edit it to get it back to how it looked in Vuescan?"

 

No, it's essentially identical (althought Vuescan's not properly color managed, so what it shows you visually isn't quite accurate).

 

I believe Vuescan works with simple non-exposure dependent profiles and does strange things when reading more sophisticated LUT-based profiles. The sophisticated profiles are slightly more accurate in my experience (but the VS-created ones aren't bad for a starting point).

 

I don't really trust VS's color processing and do trust Photoshop so I do as much in Photoshop as possible.

[mendel_leisk]

Roger, I think Rob's output is 16bit, not the darker "linear" you mentioned, aka Vuescan Raw File. He says "raw", and then describes it as having the Color Tab's None setting.

 

Anyone know: is there a difference between setting output color space to ScannerRGB (as Rob describes) and not assigning anything? I do the latter, just to avoid issues in Photoshop or whatever, but am totally clueless.

[roger_smith4]

Hi Mendel, I tested it both ways to see if there was any point to doing linear RAW with Vuescan versus "scanner (or device) RGB". There wasn't a significant difference in my testing having created profiles for a given exposure with Scarse for linear RAW and deviceRGB.

 

I stick with 16 bit non-linear gamma output where the scanner color space is set to built-in, color balance is set to "none", output color space is Device RGB, so it is not converted to any profile like Adobe RGB within Vuescan.

 

I then apply the right profile and convert to a working space in Photoshop and it works fine.

[mendel_leisk]

My second paragraph is a little bizarre (long week, need more sleep): ScannerRGB should have read DeviceRGB, and now that I'm home, and looking at Vuescan, I see *something* must be assigned for Output Color Space, default being sRGB.

 

Looks like the helpfile does not clarify what DeviceRGB is, and how it would vary, say from sRGB.

 

Out of my depth a bit here, will bow out and read up ;)

[roger_smith4]

DeviceRGB is just whatever the scanner outputs. Profile that with LCMS or Scarse (or a pay program) and then convert to a working space like AdobeRGB or Ektaspace.

[whitestone]

In my original post I should have said 'Device RGB' instead of 'Scanner RGB'.

 

Mendel - With VueScan, a scan to Device RGB has no embedded profile. (Although, I'm not convinced that it isn't doing some sort of conversion.)

 

Roger - I think I'm doing just what you are doing - color balance is set to "none", output color space is Device RGB, assign the correct profile and convert to a working space in Photoshop - but it just isn't working for me.

[roger_smith4]

Do you have other color problems with Photoshop? Photoshop is ICC aware and will convert the image on the fly to your monitor profile which is set in Windows OS. I don't think Vuescan does this.

 

Does the file with a profile applied in Vuescan look identical in Vuescan and Photoshop?

 

My only last thought is that Vuescan's profiles seem to work best with Vuescan and you might try using a program like Scarse or LittleCMS to create profiles for use in Photoshop- compare them and see which approach you like best.

[whitestone]

Roger-

 

No problems in Photoshop. My monitor is profiled, and everything seems OK.

 

When VueScan does the color management, the image looks correct and it looks basically the same in VueScan and Photoshop.

 

I tried LittleCMS and got the same results: after assigning and converting in Photoshop the image is a disaster.

[Greg Fight]

Where in Vuescan do you set the output color space? In my version (8.4.25 Standard Edition)

I don't see a menu for output color space. There is a check box for TIFF profile/no profile

(same for jpg).

[whitestone]

Under the Color tab. Maybe you need the Professional edition.