Converting RGB to CMYK

[David Milisock]

@David Milisock OK, I can agree that sRGB isn't the ideal capture space for golf (or swimingpools or other holiday resort promotion).

For images where there is a choice in workflow, I usually go CameraRaw => AdobeRGB (since the choice in ACR is very limited) => Add HSB adjustment layer while toggling Proof Colours to deal with tricky out-of-gamut colours (Using relative and BCP enabled). I leave the the images in RGB, mainly for possible cross-media re-use and it also gives the possibility to repurpose for alternative production workflow (and smaller file sizes).

Sure sRGB is fine for many jobs but the issue is this if you capture with a wide gamut you can always go to a smaller gamut and it takes nothing extra.

 

[David Milisock]

the beauty of color management: once you chop space off, you can't bring it back. Simply converting EVERYTHING first to CMYK (often using such silly defaults as AdobeRGB to US Web Coated v2) and only THEN starting retouching in CMYK (because they don't understand RGB) is a clear path to disaster - or should we say 'common practice'?

While those dark greens might be tricky in sRGB to start with, I believe that many processing tools / options are ultimately responsible for the loss you experience.

I suffer natural curiosity and would love to see what your experienced losses are and if improvements could be made (using alternative settings / tools - not hours of manual labor). So if you're up for it, drop me a line (off-list) and I'll give it a shot

The most prominant example of this affect was with a clients product shots so I will ask if I can get then and send them to you. It was a global manufacturere of childrens products. Their product was littel plastic storage bins that were multi shaded many diffeent greens. In sRGB he just couldn't get them in Photoshop to convert to CMYK with very much distinction, I suggested he try getting Adobe RGB captures ad he did. Th process was smoother and easier for him.

Myself I only use RAW and archive as 16bit ProPhoto RGB.

Attached is a 3d gamut vire of adobe RGB, sRGB and my standard CMYK overlapped on one another you'll see whay the greens arre an issue. You can't conver what you don't have.

 

[dmrivet]

Have you tried PitStop Pro?

 

[David Milisock]

Have you tried PitStop Pro?

For color conversion from RGB to CMYK?

If so yes and I prefer using either Corel Photo-PAINT, Adobe Photoshop or Paintshop Pro. The former two have better curve control but the latter will do in a pinch.

 

[dmrivet]

What I like about PSP is you can set up actions to manipulate specific areas. But yeah Photoshop has better management.

 

[David Milisock]

What I like about PSP is you can set up actions to manipulate specific areas. But yeah Photoshop has better management.

It's clear that Photo-AINTY X5 and Photoshop CS5 are more complete in terms of color editing but PSP does have som einteresting features and with a color calibrated display you can do good work.

PSP is applicationcolor managed and that has it's requirements.

 

[juergenroesch]

Attached is a 3d gamut vire of adobe RGB, sRGB and my standard CMYK overlapped on one another you'll see whay the greens arre an issue. You can't conver what you don't have.

true - but in the upper section are areas that are out of gamut already to your CMYK space. So if you do some curve reductions to get the bright greens in you usually also affect the dark greens and shrink them to where you actually really see the lack or rather loss of gamut.
Which is exactly what I meant with the squeeze ball example. Curves are like a metal ruler between your fingers ensuring that even areas get squeezed in where the destination space would allow sufficient room - example: solid GRACoL / ISOcoated YELLOW, which is already outside the AdobeRGB gamut (and not the other way round).
And in 8bit any edit will suffer quantization issues later, so a conversion sRGB to AdobeRGB or to ProPhotoRGB should always use 16bit for the destination during the color retouching / correction stage to avoid steps

 

[David Milisock]

true - but in the upper section are areas that are out of gamut already to your CMYK space. So if you do some curve reductions to get the bright greens in you usually also affect the dark greens and shrink them to where you actually really see the lack or rather loss of gamut.
Which is exactly what I meant with the squeeze ball example. Curves are like a metal ruler between your fingers ensuring that even areas get squeezed in where the destination space would allow sufficient room - example: solid GRACoL / ISOcoated YELLOW, which is already outside the AdobeRGB gamut (and not the other way round).
And in 8bit any edit will suffer quantization issues later, so a conversion sRGB to AdobeRGB or to ProPhotoRGB should always use 16bit for the destination during the color retouching / correction stage to avoid steps

Your concept sound good but when working with a catalog that has 3 or 4,000 images the need something a bi tmore automated, so RAW prophoto to Adobe to CMYK worked.. The end result was always debatable but the different green bins looked different to one another.

 

[gcplau]

What is it?

What is it?

I know of only ONE system that can do what you say (variable gamut mapping/rendering intents).



Regards,
Terry

Hi Terry,

What's the ONE system that can allow user to manipulate gamut mapping?

Thanks for sharing
gcplau

 

[TerryWyse]

Hi Terry,

What's the ONE system that can allow user to manipulate gamut mapping?

Thanks for sharing
gcplau

Just to clarify, I'm not saying there's only one system that allows adjustable gamut mapping, just that there's only "one that I know of". That system is GMG. If there's others, I'm not aware of them.

Terry

 

[gcplau]

Tks

Tks

Tks for the info, which module of GMG product do this?

Don't mean to question if it's the only one, but just happen to quote your say and your say make the "ONE" all cap.

Cheers

 

[TerryWyse]

Tks for the info, which module of GMG product do this?

ColorProof and ColorServer will do it. The real power of their gamut mapping and "variable rendering intent" (my term, not theirs) is when creating RGB-to-CMYK MX4 profiles. Keep in mind that these are "proprietary" device links that can only be used within GMG's software products.

Terry