Questions on Change Profile

[Robert Schleif]

In the Change Profile transformation in addition to names of profiles like Adobe 1998, I find a number of Canon papers listed, e.g. Canon PRO-1000/500 Photo Paper Pro Premium Matte. (I have installed a Canon Pro-1000 printer.)
1. Is the information on the Canon papers in the printer drivers, or rather, where did the information come from?
2. When selecting a paper output in the transformation, does the transformation try to mimic what the input image will look like on the selected paper? At least that is what a simple test suggests. With the working space and monitor profiles set at Adobe RGB 1998 a magenta color (R=200, G=0, B=200) is brilliant on my monitor, but prints as a dull sort of pink where other colors print correctly. The change profile with the output profile set for the printer paper very closely reproduces the dull pink.
3. In general, it seems like the printer drivers tell the printer how much ink to use to make the print "match" the image profile, but the Change Profile seems to do the reverse in that it seems to calculate what the printed image will look like with some fixed allocation of ink amounts. What is really going on or what should I read to understand?
4. What is the relationship between Proofing as described in Color Management and what the Change Profile transformation is doing?

[jsachs]

When you install printer drivers, typically printer profiles are installed at the same time.

To preview what the image will look like when printed, you set the Proofing profile in PWP's color management settings. You can also set a gamut alarm which will warn you when colors you see on your screen are outside the printer's color gamut. I do not recommend using Change Profile to change to the printer profile which is only intended for use while printing images. There is some additional information on this in Color Management.pdf.

There are several problems that make prints not match the screen:

1) If your monitor brightness is too high, the prints will be too dark. Prints also look very different depending on the brightness and color of the light they are viewed under.

2) Printers have much lower contrast between pure black and pure white than monitors.

3) There are colors the monitor can display than can be printed and also colors that can be printed but not displayed. Generally monitors are better at bright RGB primaries and printers are better at dark CMY secondary colors.

[Robert Schleif]

Thank you. What you wrote plus additional reading answers my questions. Trying to print a beautiful Impatiens flower brought on this study and the eventual discovery that the flower's color and intensity are far out of gamut for the Canon P-1000 printer using any Canon paper. It seems like it would be useful if the print preview button on the main tool bar had the option of turning the gamut alarm on and off rather than having to go through File Color Management to do this. It might also be useful to have a new transformation "Gamut" which combines the paper choices of "Change Profile" with the ability to turn the gamut alarm on and off.

[jsachs]

There is a button on the main tool bar that toggles proofing if a proofing profile is defined. There could potentially be another button to toggle the gamut alarm if you think that is useful.

As you probably already know, you can achieve a much wider color gamut and contrast range if you print on glossy paper.

[Robert Schleif]

After experimenting for a while with a number of old images, I'm finding that I would rarely use the gamut alarm, and instead, I will toggle back and forth between the monitor image and proof image. Therefore, in the interest of a clean screen, I, myself, do not now
advocate for an additional button on the main tool bar.
I find that the ability to preview images printed on different paper types that is possible using Change Profile is quite useful. I stumbled upon this by accident. Possibly there is a way to make this capability more apparent by changing its name? (Without, of course, adding another icon to the main tool bar.)
Thank you for the reminder that glossy papers have a wider gamut than matte papers. Canon paper Pro Crystal Grade does the best a displaying the color of the impatiens flower that started me on the gamut path.

[jsachs]

I already added a gamut alarm button for the next release.

I also added a new section at the beginning of Printing.pdf that discusses some of these issues.