Luminous Landscape Forum

Raw & Post Processing, Printing => Colour Management => Topic started by: bns on March 28, 2013, 03:09:42 pm

Title: No perceptual rendering in Ilford profiles?
Post by: bns on March 28, 2013, 03:09:42 pm

I am using Ilford Galery Prestige Smooth Gloss, Smooth Pearl and Gold Fiber Silk in combination with an Epson R3000. I have the Ilford provided profiles for these combinations installed.
While softproofing in LR4.3 (W7-64) I do not see any difference at all between using relative or perceptual  rendering, even for images that contain plenty out of gamut colors.

It looks like the Ilford profiles simply do not support perceptual rendering. Why would they do this? Or am I missing something?

Boudewijn

Title: Re: No perceptual rendering in Ilford profiles?
Post by: digitaldog on March 29, 2013, 09:26:54 am

I've never heard of such a thing but I suppose it's not impossible. Are you on a Mac? You can check out the tags using the ColorSync utility. Or just convert two images using both options for rendering intent then use this technique to subtract and examine:

http://digitaldog.net/files/Apply_Image.pdf

Title: Re: No perceptual rendering in Ilford profiles?
Post by: bns on March 30, 2013, 08:49:59 am

Hi Andrew, thanks a lot for your reaction. I have a Windows 7 machine, but I followed your suggestion as outlined below.

In Lightroom I used an image of a bunch of color patches and printed this image to a jpeg file using different profiles and both relative and perceptual rendering intents.
The profiles I used as examples are:
- Ilford: n_GPSGP12_EPSr3000_EPGn
- Epson: SPR3000 Epson Premium Glossy
- Home made profile for Epson R3000 and Ilford GPSGP12 paper (Colormunki + ArgyllCMS)

A single example of the resulting 'JPEG prints' is attached (Ilford profile).

The differences between the 'prints' made with relative and perceptual intent are also attached (subtracted perceptual from relative). The Epson profile, as well as my home made profile, does show clear differences between the two rendering intents. In the case of the Ilford profile differences are present, but they are very small indeed.

So, I was wrong in the sense that the two rendering intents of the Ilford profile are not identical, but the difference is extremely small. One could say that this analysis illustrates the rather significant differences in algorithms used by different companies, or methods, for color 'compression' in the perceptual rendering intent.

Boudewijn

Title: Re: No perceptual rendering in Ilford profiles?
Post by: mac_paolo on March 30, 2013, 12:57:27 pm

I custom profiled the GF Silk for my R3000.
For the most of non hypersaturated shots, the difference is minimal between the two intents.
You have to have a very good display to appreciate that.

With oversaturated greens and reds (Ultrachrome K3 VM doesn't have them), the difference between the intents is more than evident.