Need advice with 'Convert to profile' please

imonk

Hi all,
I took this picture of my friend's car the other night as part of a test shoot. I PPd in Capture NX 1.3 which applied my monitor colour profile (created using a Huey pro). I then took the file into photoshop CS2 for final contrast and sharpening (and some cloning of a cracked bumber).



Now at this point I always use 'convert to profile' and save a copy with sRGB for web viewing and I never really see any colour shifts but with this image (and others from the same shoot) the blue of the car turned more purple. It should be a nice blue.

Does anyone know if there's any steps I'm missing out or if I shouldn't be applying the monitor profile in Capture NX? I did try from RAW again but getting NX to apply aRGB but I still found the same colour shift at the end

I've looked up alot on these boards and others and can't find anything so I'm thinking there isn't any other options but I thought I'd try you guys before giving up

Any help/advice much appreciated.

Cheers
Ian

arodney

The first problem was assigning a display profile to the image. You don't want to do that! A display profile is only used for color management aware software to properly preview the RGB values based on the processing. I don't use NX so I can't tell you what to pick but I suspect you'd want something like sRGB, Adobe RGB (1998) or ProPhoto RGB since these are working spaces (color spaces for image editing).

See: http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf

imonk

Thanks Andrew,

That was my first thought also so I tried setting up NX to assign adobeRGB instead. What I found was that when I came out of NX it was slightly more purple already and then I still got the rest of the colour shift in PS when converting to sRGB.

Any other thoughts?
Ian

arodney

imonk wrote:

Thanks Andrew,

That was my first thought also so I tried setting up NX to assign adobeRGB instead. What I found was that when I came out of NX it was slightly more purple already and then I still got the rest of the colour shift in PS when converting to sRGB.

Any other thoughts?
Ian

I wish I could help you with NX but I've never used it. That said, products like Lightroom, Camera Raw, Bibble and other converters I've used show no difference in color inside the products and the colors when exported and brought into Photoshop match as well. The color space shouldn't matter here unless you're somehow getting untagged documents out of the converter, then Photoshop takes a guess, based on your color settings as to what the color space is. So say you export out in ProPhoto RGB which I use. IF Photoshop got that document but it had no embedded profile, Photoshop would not "know" its ProPhoto RGB and, unless my color settings were set for ProPhoto RGB, it would use another assumption for the data and this would result in a mismatch.

But if color management is properly setup, and say you export the document as ProPhoto RGB then decide you wish to have a copy in sRGB for the web, converting would not alter the color appearance. The RGB numbers would change, the color appearance would be honored. You can try this in Photoshop by opening a document in one RGB working space and convert to another, (ProPhoto to sRGB), and within Photoshop, the color appearance should remain nearly identical.

imonk

Aye that's exactly how it normally behaves. I used to use 'assign' to profile until someone pointed out that I should use 'Convert' which will retain the colour appearance and since then I've never had a problem. I use AdobeRGB for everything and usually convert to sRGB for web pics or for sending to clients. However, there must be something about these particular images that is fooling the colour settings because the blue really noticeably changes when I convert I'm a bit confused, which isn't hard!

arodney

imonk wrote:

Aye that's exactly how it normally behaves. I used to use 'assign' to profile until someone pointed out that I should use 'Convert' which will retain the colour appearance and since then I've never had a problem. I use AdobeRGB for everything and usually convert to sRGB for web pics or for sending to clients. However, there must be something about these particular images that is fooling the colour settings because the blue really noticeably changes when I convert I'm a bit confused, which isn't hard!

You use Assign IF the document has no embedded profile or, for some very odd reason, the wrong profile was assigned. It doesn't change the numbers, it changes the scale or definition of the numbers.

Convert changes the numbers.

I suspect the problems are some setting in NX but I can't help further not knowing what it does. If its embedding the correct profile, the color appearance should be the same as seen in Photoshop.

imonk

Hmm that's a good point. I should have thought about cutting NX out of the loop altogether to see if that makes a difference. I might try using photoshop to convert from RAW then pp and see what diff that makes.

Cheers
Ian