Visual white point and PCS behavior

Home Forums Help and Support Visual white point and PCS behavior

Viewing 5 posts - 1 through 5 (of 5 total)
  • Author
    Posts
  • #141348

    Guillaume
    Participant
    • Offline

    In fact I’m asking if using a visual white point could potentially change the behavior of the PCS. If I want to softproof at D50 with a monitor calibrated at the visual white point, with absolute colorimetry, would the PCS take into account the deviation from D65 ? Or will it force the D50 and distort the colors without the adjustments of the visual white point ?

    #141352

    Vincent
    Participant
    • Offline

    softproof is relative whitepoint to monitor. On that whitepoint a white paper correction (relative to current white) is applied because white point monitor is expected to visually match reference ambient lit for printed copies. The rendering intent you see on some image viewers is about printer profile to image, not display.

    An example: a -7b* paper on a D50 printer profile softproofed on a D65 monitor will show an even bluer (an additional -7b*) than D65 white.

    If you want to softproof at D50 whitepoint you need to calibrate to D50 or use some 1D calibration or 3DLUT. Remember that most suits only check whitepoint and app startup, so changing display profiles implies app restart (unless both profiles match at gamut & TRC)

    #141355

    Guillaume
    Participant
    • Offline

    I understand that relative colorimetry or perceptual is the best. But if I want to check how it will look under a D50 light booth, without changing the profile from visualy matched D65 to visualy matched D50, an absolute colorimetry intent is better. But yes, here, the color profile switching method seems to be an even better approach, less easy but better. I already thought about it in fact. How would it works on MacOS as the OS is color managed ? Should perceptual intent looks like the same as Windows ?

    #141362

    Vincent
    Participant
    • Offline

    If you want D50 use D50 as calibration target.

    If your display has only 1 “custom/user” slot/preset and no hardware calibration, so you are forced to share settings, calibrate to D65, then try an absolute colorimetric LUT3D+DWMLUT on Windows, simulating a synthetic ICC profile with same primaries as your custom profile, same TRC (beware on balck level if it is not BPC) and D50 white. Use no embeded VCGT in LUT3D.
    You open Photoshop , edit as usual on your cutom D65 calibration on user mode. Then when trying to simulate D50 load LUT3D in DWMLUT. Since TRC is the same, black level is teh same, gamut is the same and rendering intent from image to screen (not form image to paper) is always whitepoint relative, color maths in Photoshop should be close enough to use with your custom ICC D65 profile on OS… but with a LUT3D to D50 on top of it running on GPU shaders.
    Of course D50 will be simulated at the expense of unique grey levels, since white is D65. DWMLUT uses dithering so it should be no noticeable on a well behaved 8bit or better display

    AFAIK there is no tool like DWMLUT on macOS. Adobe suite will use its own ACE engine on macOS so the same “always whitepoint relative” will apply for rendering image to display. You won’t simulate D50 that way.
    You may try to switch to a custom D50 calibration on D65 OSD settings, so whitepoint will be corrected through VCGT… but if you wish to not re open Photoshop that 2nd display profile must have the same gamut TRC & black level.

    • This reply was modified 1 month, 2 weeks ago by Vincent.
    #141396

    Guillaume
    Participant
    • Offline

    Sorry for the very late reply, I was busy and I didn’t want to make big posts.

    So I don’t really need to bother as long as I do a relative or perceptual softproof. The only thing I need to do is to calibrate a monitor, that doesn’t make a too big eye metameric failure, to D50 and visualy match the CCFL one.

    The main advantage with MacOS is that it applies the profile system wide so using 3D LUTs is not necessary.

    What does TRC stand for ? I knnow it’s gamma related but knowing it would be nice.

Viewing 5 posts - 1 through 5 (of 5 total)

You must be logged in to reply to this topic.

Log in or Register

Display Calibration and Characterization powered by ArgyllCMS