Hi Doug,
I had nothing clear about the use of M0 or M1.
But it seems more consistent the use of M1 through the entire process of creating the profile and softproof, measuring at 5000ºK (M1), use of 5000ºK for illuminant (CIE D50), and setting the monitor color temperature to 5000ºK for printing.
Another thing is to use specifics lightings depending on where shows the print.
This was my thinking when choosing M1, but at anytime I can change if I understand and share the reasoning, because I own all the measurements (M0, M1, M2).
You can expand the comments about this question?
Regarding the list, I find a little unexpected the results of Hanemuhle Photo Rag 308. Your results for this paper are similar or different?
Last, all the paper on the list are Hahnemuhle, unless otherwise stated.
Thanks!
Hi Nick,
Well, this is quite an interesting topic and one that, I'm afraid, is not well understood even by many folks that are quite expert at color and printer profiling.
Here's what the M0, M1, and M2 is in a nutshell. M0 represents measurements where the illuminant has a bit of uV and approximates the uV from a tungsten lamp which is less than the uV from daylight or D50. M1 represents typical daylight proportions of uV and M2 cuts off uV.
Let's look at the issue of D50. D50 is more than a "White Point," or x,y coordinate in CIE 1931's two degree colorspace though it is also that. It's a slightly ragged spectral distribution that includes uV light that isn't, itself visible. All ICC colorimetry uses D50 as a reference illuminant and combines this with the reflectance spectrum of the print medium in order to create profiles. This is true for M0, M1, and M2 measurements. They all use D50 but for media that has no fluorescent components the uV portion of D50 makes no difference at all and M0, M1 and M2 would produce identical results. What happens with uV (wavelengths below 400 nm) is that it isn't reflected but absorbed by the paper's surface and re-emitted in longer wavelengths. This process is called fluorescence. Most paper with OBs will have significant bluish tints as the invisible shorter wavelengths that comes back as visible "blueish" wavelengths around from 400 to 450 or so causing a blue shift and making the paper "brighter" as well.
Outside of B&W prints there is relatively little difference in how prints will look with one big, but rarely used, exception. It makes a great deal of difference in Absolute Colorimetric Intent. For Perceptual, Relative, and Saturation Intents profiles follow the White Point of the paper and Lab 100,0,0, or RGB values of 255,255,255 will lay down no ink. You just get whatever the paper "white" is and you see other colors in that context. Paper Whites with OBs typically will have a Lab "b" value of between -5 and -10. If the print has OBs and is viewed outside, it will look more bluish than it will inside but so will the overall print. This is because the ink coverage is only partial, some uV leaks through, and some of the bluish fluoresced light comes back to the viewer. The lighter the color the more fluoresced light comes back. It isn't perfectly in proportion but the effect is gradual and more likely to only show up only in B&W prints where small coloration change can be more easily seen.
Absolute Colorimetric Intent is a different kettle of fish. Selection of "M" mode makes a huge difference because this mode attempts to adjust the colors printed to match the Lab values without scaling it to the paper's White Point. As a result if you print Lab=80,0,0, a very light gray, a bit of yellow will be added to the gray to bring the "b" from its negative value to 0. This might work in sunlight but inside the print will look rather yellowish. The only way to use Absolute Colorimetric Intent correctly is on paper w/o OBs or on paper that is displayed with a museum quality uV blocking glass. Still, Absolute Intent is not commonly used because it will block fine gradations from L=that of the paper white to L=100. It's really only for either accurate reproduction work where you are working with colors that are exactly that of the thing you are reproducing, or creating exact colors - usually an industrial process. So, for AI, you want to make profiles using M2 to eliminate the fluorescing component then use a uB blocking coating or glass.
But back to normal photos and display. The effects are more subtle than AI but still there. For instance if you have a profile made with M1 or, to a lessor extent M0, then print a light gray and it lays down a thick light, light gray pigment you can see a blue shift indoors. This is because the pigments used don't fluoresce but they do block the uV light from reaching the paper when making the profile. The profile tries to shift the colors in these gray areas toward the blue to match the bluish white point created by the uV in M1 or smaller M0.
So, in summary, if you make profiles with M1 then display indoors or under museum glass or use a uV blocking coating then you can see some color shifts. Especially in B&W prints. It's a smaller effect with M0 and if you show under tungsten with normal light indoors it will appear correctly w/o a color shift. So stay away from M1 unless you are showing outdoors.
OTOH, if you do want to use a uV blocking museum glass or coating then make profiles using M2 which blocks uV from and fluorescence when making profiles. The profiles will then match the actual paper white when viewing w/o any uV.
As for making profiles with other illuminants than D50 such as LED lights or some of the fluorescent lamps, the profiles will be adjusted so the colors will appear correctly under those illuminants. Whether M0, M1, or M2 should also be chosen depends on how much uV is coming out of the lamp. This is best tested experimentally.
