Can't figure out how to tweak an existing profile

[Gregg]

I am trying to create a CMYK profile for our jacket files. They all print on sheetfed presses, so I planned on starting with the U.S. Sheetfed Coated v2 profile that is already in Photoshop and then slightly edit it. That profile has a total ink limit of 350 which is too high for the printers I use. What I can't figure out how to do is edit that profile to create my own.

If I have that profile established as my working space and then go to Color Settings - Working Spaces - CMYK - Custom, I was asuuming that it would bring up the specs of that profile and then I could make eidts and save out as something different. But when I go to custom it just always defaults to SWOP (Coated), 20%, GCR, Medium, which an ink limit of 300, so I know it is not the same profile.

Can anyone offer some advice?

[clod]

If I have that profile established as my working space and then go to Color Settings - Working Spaces - CMYK - Custom, I was asuuming that it would bring up the specs of that profile and then I could make eidts and save out as something different. But when I go to custom it just always defaults to SWOP (Coated), 20%, GCR, Medium, which an ink limit of 300, so I know it is not the same profile.

Can anyone offer some advice?

ICC proflies can only be edited in a specific profile editor. When you go the route of custom CMYK as you mentioned above, you are dumping your current profile and using Photoshop's own antiquated CMYK engine to create a new profile, which is not based on press characterization data at all...neither is the Sheetfed profile, which actually is based on Commercial Matchprint data. The US Web Coated SWOP v2 profile if built from the TR001 data set collected from a series of SWOP press runs , and also widely adopted in the sheetfed community (watch for updates to both SWOP and TR001 coming soon). But anyway, if you want to edit any existing ICC profile, you need a separate, 3rd party profile editor...maybe in a future version of Photoshop.

[Gregg]

Thanks, clod. Great info.

I do have a follow-up question I was hoping you could help with.

I feel like I have a general understanding of color management, but this is one thing that I cannot get my head around.

Say I have an image that was converted from Adobe RGB to US Web Coated v2. So the image is now CMYK and the darkest shadows are in the 280 range. Where I get confused is that I can now make a curves adjustment and blast those shadows to well over 350 and there is no sort of gamut or ink limit warning in my info palette. And then when I re-save the file (embedding the US Web Coated profile) it does not bring the numbers down under the specified ink limit. So now I have a file with an embedded profile that has an established ink limit of 300, but my shadows are 350.

Am I wrong when I thought that once the image was mapped to the proper CMYK profile that it would not allow the numbers to go higher than the profile dictates?

[Damo]

Originally Posted by Gregg

But when I go to custom it just always defaults to SWOP (Coated), 20%, GCR, Medium, which an ink limit of 300

Hi Gregg,

Clod is right, Photoshop's profiles are very simple compared to true ICC profiles.

If I can attempt a clumsy explanation ...

Imagine a hexagon drawn on a page, and a dot in the middle. If you draw a straight line from the dot to each of the six corners of the hexagon, that's a simple Photoshop profile. The dot is neutral, and each of the six points are the saturated C, M, Y, CM, CY & MY.

However, a complex ICC profile is more like a spider's web. No straight lines between neutral and saturated, and lots of points along the lines with specific values that form the LUT (look-up table), and can only be edited with a specialised profile editor.

(Gee I hope that makes sense!!!)

However, don't give up on Photoshop. It is capable of creating very accurate profiles for you if you are in a closed-loop environment. It's tricky to get them right, but hey! You own Photoshop already, so you don't need to pay a cent for new stuff. Worth a shot.

So now I have a file with an embedded profile that has an established ink limit of 300, but my shadows are 350.

Yes, it's one of those funny things about Photoshop. It's true that it's a bit dangerous to be able to over-ride ink limits. If there's any doubt, always check your shadow values in the Info palette.

But at the same time, it's important to have that freedom and control. If I have a logo converted to SWOP CMYK, and the brightest blue it gives me is 92C 94M, I can add the extra 14% of colour to achieve 100C 100M.

That's one example ... I'm sure there's many others. Frankly, we have that flexibility because we're professionals working with an Adobe product. If Microsoft made Photoshop, it would be aimed at plebs, and you can bet that the limits would be rigidly maintained!

All the best,

Damo.

[clod]

Say I have an image that was converted from Adobe RGB to US Web Coated v2. So the image is now CMYK and the darkest shadows are in the 280 range.

US Web Coated should be about 300 actually...

Where I get confused is that I can now make a curves adjustment and blast those shadows to well over 350 and there is no sort of gamut or ink limit warning in my info palette.

Indeed. Curve adjustments in CMYK will allow adjustments up to 400% (100% of each channel). Its quite logical, but it can be quite problematic in the wrong hands (or even in experienced hands...I've seen 20 year veterans hose an image this way). This is one of the benefits of editing in RGB. No matter how far you crank the curves, upon conversion, you'll never be over the total area coverage of the CMYK profile you're converting to. Not only that, but making simple overall contrast moves to CMYK will quickly alter color no matter if you want it to or not, potentially causing gray balance issues, where as the same contrast move done in RGB will not alter gray balance. Try it yourself by creating two identical RGB images with a white to black gradation. Apply an "s" shaped curve to one of them and convert to CMYK. For the other, convert to CMYK, then apply the curve. The image whose adjustment was done in CMYK is much more apt to impart a color cast to the gray balance.

[Gregg]

[quote="clod"]

Try it yourself by creating two identical RGB images with a white to black gradation. Apply an "s" shaped curve to one of them and convert to CMYK. For the other, convert to CMYK, then apply the curve. The image whose adjustment was done in CMYK is much more apt to impart a color cast to the gray balance.

Wow, very noticeable color shift with the pre-converted CMYK file. Man, I feel like I learned a great deal from this post alone. Thanks alot.

I really never thought about the ink limit issue as another benefit of doing all color work in RGB. Makes total sense though.

[dimitri]

now the question is, why does "assign profile" or "convert to provile" not do the job. I would expect this. however, when i tweak curves and i get too dark, i do the same thing, back to RGB and then i convert again to CMYK. you don't loose anything, as rgb should be a bigger color space.
the question is, which RGB profile do you use for that?

and i agree, photoshop should have a feature like indesign to highlight areas over your desired inklimit. often i place a photoshop image in indesign, just to check if it goes over my inklimit.

dimitri

[wally]

Originally Posted by dimitri

and i agree, photoshop should have a feature like indesign to highlight areas over your desired inklimit. often i place a photoshop image in indesign, just to check if it goes over my inklimit.
dimitri

Make a black adjustment layer set to solid color, above your image with your maximum black color. Create another adjustment layer as threshold above the black layer.
When you move the threshold slider right up to the threshold of your black, it will be set to your max ink.
Discard the adjustment layer with your black solid and now whenever you click the threshold adjustment layer you can see if your edits are going over your max ink.
It won't matter if it's a different color that goes higher than your max because threshold is now set for max ink.