ColorSpace Question

[IanBarber]

For simplicity, assume I working in Lightroom which is more or less ProPhotoRGB ( Melissa) to be precise. Assume I am using a paper ICC profile, when I hit the print button, does the colorspace get changed as hit reaches the printer at all ?

[howardm]

Yes.  No printer is even vaguely capable of ProPhoto so the function of the profile is to transform/map the data from ProPhoto to whatever the printer can do (it's own personal output space).  ProPhoto is just a working space and LR is doing a conversion from ProPhoto into L*a*b* (called the PCS printer connection space) and then the ICC profile takes that PCS space data and converts again to the printer space,

[IanBarber]

Thanks for the explanation.


I am assuming that with the Advanced Black and White driver which is not ICC managed, all bets are off and the test is what pops out of the printer based on the settings we have available in the driver settings.

[Jim Kasson]

Yes.  No printer is even vaguely capable of ProPhoto so the function of the profile is to transform/map the data from ProPhoto to whatever the printer can do (it's own personal output space).  ProPhoto is just a working space and LR is doing a conversion from ProPhoto into L*a*b* (called the PCS printer connection space) and then the ICC profile takes that PCS space data and converts again to the printer space,

Andrew will correct me if I get this wrong, but I believe in some ways you have oversimplified things and in one way overcomplexified them. I will assume an Epson inkjet printer and color mapping outside the printer driver (not "printer picks colors"). Lr (possibly with some support from the OS) maps the colors in the images using an ICC profile to an RGB representation that is sent to the printer driver. The printer driver takes the RGB representationn, halftones the image using error diffusion plus added noise, maps it to CMYK, CcMmYKk, CcMmYGOKk, or some other printer colorant representation.

Although the transform from Lr's native color space to the RGB space that the printer driver takes is dependent on separate ICC-mediated transforms from Lr's space to Lab and from Lab to the printer driver's RGB, once those are known, a 3D loolup table can be constructed to take the image directly from Lr's working space to the RGB space the printer driver will accept, without going through Lab.

Jim

[howardm]

I'm sure many colors were harmed in the construction of that posting

I was just trying to clarify that the data goes through several transformations on it's way from ProPhoto to the printer data.  I thought it was clear that the OP was interested in 'Photoshop (LR) Manages Color' kind of work, not having the printer control the colors.

Isn't what you're referring to in your second paragraph what is known as a 'device link' profile?  Seems to me that the tradeoff is possible (very small) numerical resolution/conversion errors vs. trying to create a profile that does 2 conversions.  I think the difference is something like N^2 vs. 2*N in the number of profiles that would have to be made so that isn't really super-scalable.

[digitaldog]

Assume I am using a paper ICC profile, when I hit the print button, does the colorspace get changed as hit reaches the printer at all ?

Not sure I understand the question. ProPhoto RGB (or the unnamed internal LR processing color space that has ProPhoto RGB primaries and thus it's gamut) is converted to the output color space of the profile you selected. IOW, there's no such thing as a ProPhoto RGB (or sRGB) printer.
FWIW, MelissaRGB is the color space used for the Histogram and RGB  percentage values outside of soft proofing. It does use ProPhoto RGB primaries but it's not using a linear TRC. That's the differences between it and the unnamed internal color space that's actually used for processing.

[IanBarber]

I was just unsure what happened when it left LR in this case or id could be Photoshop for that matter. Now I understand that ICC profile maps the colors in accordance with what the printer is capable of producing.

[Mark D Segal]

The gamut volume of ProPhoto RGB is 2.5 million and that of an Epson 4900 printer using Ilford Gold Fibre Silk paper (the widest gamut I have achieved with a printer) is 977,000; therefore to the extent the image file has values reaching somewhere in ProPhoto space beyond the gamut volume of the printer profile, there will be gamut compression, the nature of which depending on the Rendering Intent. As for the internal algorithms, my understanding is that there are two profiles at play - the colour space embedded in the image file and the printer profile. The two talk to each other through the Profile Connection Space in the operating system's Colour Management System and this talking is done using L*a*b* values. We work the image in RGB, it gets translated under the hood into L*a*b*, then connects to L*a*b* values in the printer profile, which then get translated into RGB values that the printer space can accommodate, the manner depending on the Rendering Intent. The printer driver than takes those RGB values and converts them into the colours of the inks (CMYK plus others depending) that will be used in print.

[Schewe]

For simplicity, assume I working in Lightroom which is more or less ProPhotoRGB ( Melissa) to be precise.

Actually, you are wrong (don't assume anything dooode). ACR/LR works with ProPhoto RGB in a linear gamma space (Melissa is PP RGB in an sRGB gamma).

Sorry, the rest of your question is pretty much blown out of the water by your innate lack of understanding of Color Management. Of course what you set in the print settings impacts what you get out of the backside–DOH...you didn't need to ask, you really already knew the answer.

[IanBarber]

Actually, you are wrong (don't assume anything dooode). ACR/LR works with ProPhoto RGB in a linear gamma space (Melissa is PP RGB in an sRGB gamma).


–DOH...you didn't need to ask, you really already knew the answer.

Not quite sure what dooode means but its sounds trendy. Sometimes it's nice to have the reassurance from other people with knowledge in the area, so I guess I did need to ask.

[Ferp]

I am assuming that with the Advanced Black and White driver which is not ICC managed, all bets are off and the test is what pops out of the printer based on the settings we have available in the driver settings.

I addition to any other points raised in this thread, ABW requires "Printer Manages Colours" to be set.  This has implications on Windows, as any image with an embedded profile will first be converted into sRGB.  This issue was discussed by Adobe engineer Dave Polaschek in the comments section to a couple of threads on The Online Photographer

http://theonlinephotographer.typepad.com/the_online_photographer/2015/07/andrew-rodney-on-the-importance-of-custom-printer-profiles.html
(note the featured comment at the beginning of the comments.  There is a shorter reply from Dave about 3/4 down the page)

http://theonlinephotographer.typepad.com/the_online_photographer/2015/10/photoshop-vs-printer-managed-color-printing.html
(note final comment at the end of the comments section.  Good luck in understanding it!)

I've read these several times, and I *think* it applies to both PS and LR on Win, but not to OS X, provided that there's an embedded profile.   The situation reverses if there isn't an embedded profile, as I understand it.  I.e. it will work on Win, but I believe that on OS X you will get a profile conversion.  All this complicates ABW printing considerably, IMHO.   I assume that most people ignore all this and just live with the results.