soft proofing for a canvas print

[stuck]

I am editing an image with the intention of getting it printed as a 80 x 40 cm panorama canvas print. The company I intend to use is one I've used once before, for a large B&W canvas. That B&W image came back a bit more contrasty than I expected but it was still acceptable. In light of that experience, this time I asked the company about the ICC profile they use for printing. They replied, "...use the Adobe RGB 1998 colour space and to check the colour reproduction with Forga 39."

So far so simple, my image was already in Adobe RGB and it was easy to add a soft proof layer set to FOGRA39. Then I realised I needed to know the rendering intent. Their reply to that question was not straightforward. They said, ''We use a specific mixture of different colour intend rendering methods. For colours in the middle of the spectrum, we use RELATIVE COLOURIMETRIC and for colours on the borders of spectrum we use PERCEPTUAL.''

Given that I suppose that in order to get some idea of what the end result might look like I need to add a second soft proof layer and have one set to Relative and the other Perceptual and then compare the image with only one soft proof layer active at a time.

Thoughts please!

[Manfred M]

Their answers are quite confusing as they have effectively told you to use two difference colour spaces; Adobe RGB (which is a RGB colour space) and Forga 39 which appears to be a CMYK colour space. The answer on rendering intents is quite strange too because in general, we tend to use either relative colorimetric or perceptual, but not both and in fact,I have trouble seeing how you can emulate what they are suggesting in soft proofing. Relative colorimetric preserves the integrity of the colours that are in gamut and changes the colours that are out of gamut so that they match the colours on the "hull" of the colour space. The perceptual rendering intend evenly distributes both the in gamut and our of gamut to preserve tonal distribution, but by doing so, the colours that are in gamut may be changed.

My suspicion is that they are using a RIP (Raster Image Processor) to map from Adobe RGB to Forga 39 and are doing something weird and wonderful with the rendering intents. While the way that Relative Colorimetric behaves is pretty consistent throughout most RIPs, the way that Perceptual is handled is not.

Most custom printer makers I have used provide me with test prints to review before they run the main job. These are generally a part of the image and printed much smaller than the full-size print and in my experience, that is the only way to judge what the final product will look like. Soft proofing is not necessarily going to give you a good view of what the final print will look like.

I would soft proof with the Forga 39, not the Adobe RGB. I would run a check to see how much of the image is out-of-gamut (OOG). If nothing is OOG, then the rendering intent is irrelevant. If there are some OOG areas, try soft proofing in both Relative Colorimetric and Perceptual to see what the difference is between these two approaches. I find often the differences are fairly minor, especially if the OOG colours are fairly minimal and either works. I have also run into cases where one can see a major difference and that is more challenging to deal with.

[stuck]

Thanks, that was helpful.

The company is not a custom print maker, it's a (mass market) website so I was surprised to get any sort of reply from them when I asked about an ICC profile. I think I've now got a version of the image that will come back near enough to be good enough for me.