I have been trying out various different printing companies for printing out different things, many indicate that the image/pdf should be provided with an embedded CMYK profile but dont seem to care what CMYK profile is used as they say CMYK just says the level of ink to be used.
Some background:I've done some playing with RGB profiles and think I have the gist of it, that no (8bit) colour model can represent all colours and therefore different colour models can map the values in your image to slightly different colours. So for example using adobeRGB instead of sRGB allows the mapping to brighter colours, i.e 255 Red represents a more vivid red then 255 Red in sRGB but at the expense of having less values to match more muted reds, so the reds are spread more thinly. And Ive done soft proofing in Lightroom to see when images are out of gamut for a particular profile.
Then I tried softproofing to the CMYK profile my printer company uses and see if I can make adjustments in original image to remove all Out of Gamut and if I cannot without severely altering the image i would then compare relative and perpetual rendering and provided the image with the CMYK profile using the rendering method (perceptual or relative) I preferred. This way I control the rendering used, I would not have this control if I just provided the company with a sRGB profile
But other companies just say provide it as CMYK, and don't care to tell me what CMYK profile the printer uses. My original thought was if I provide it as CMYK profile 1 and they are using CMYK profile 2 then I could have a problem because they will convert it again, in which case colours would change. Or is CMYK non negotiable and I can actually experiment with any CMYK profile and use the one that does the best translation because the printer is just concerned with the final C, M, Y and Black values for each pixel ?