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Dear Roger,
If you’re going to pick nits (I can’t believe I just wrote that!) you really want CDT not CCT.
Keep in mind there are two white locii, which on the 1976 spectrum locus are offset by a consistent Duv.
Of course, targeting a specific xy is unambiguous, but xy measures is utterly non-intuitive numerically.
And what if you can’t quite hit your target white? DisplayCal’s white point calibration assistant helps finding the best visual fit to your target white by reporting a VDT (what Graeme terms “visual daylight temperature”) which is on the daylight locus and includes a helpful dE’00 distance (Macadams ellipse) around your target illuminant. In some cases the best visual fit will be a sacrifice of accuracy along the CCT yellow/blue longitude in exchange for better visual conformance by an move along green/magenta latitude. By seeking the lowest dE’00 at 5000 VDT, you get the best visual fit your HW can deliver.
You can see why this works with a tool like the OSRAM color calculator, which lets you project Macadams ellipses at points along the Planckian and Daylight locii.
Now, do keep in mind my main “application” is PrePress. By definition, I *don’t* live in a D65 world : if I can’t get decent *****D50***** White point out of this Dell monitor, whatever the price, $1,000, then I will quickly get it off my desk.
That’s another different story that you had not clarified before or what we may have misread.
D50 may be way off what OSD controls of a general purpose 43″ monitor can offer, and for its price & size… it is. Same for a similary priced TV.
Not getting D65 on such display will clasify it as faulty as I said previously, but aiming to D50… maybe off limits for a common display
Here is a lof of Gains / Chromaticities / CCT / Luminance :
1 Raised Red from 227 to 255 ; Y = 98 / CCT = 4028 K
x 0.3747
y 0.35912 Red 255 Green 173 Blue 153
Y = 100 / CCT = 4686 K
x 0.3494
y 0.32523 Decide to raise Green from 173 to 181
x 0.3476
y 0.335
CCT 4822 K4 Decide to raise Green again, from 181 to 191
x 0.3461
y 0.3473
CCT 49445 Raised the Green again from 191 to 195
x 0.3456
y 0.3501
CCT 4975
Y 1156 Raised Green from 195 to 200
x 0.3449
y 0.3546
CCT 5017
Y 1187 Increased Blue to 150
x 0.3462
y 0.3750
CCT 4979
Y 1208 Decrease Green from 200 to 197
x 0.3471
y 0.3549
CCT 4937
Y 1159 increase Blue from 150 to 152
x 0.3452
y 0.3521
CCT 4997
Y 11710 increase Green from 197 to 199
x 0.3447
y 0.3546
CCT 5028
Y 11810 Decrease Blue from 152 to 151
x 0.3463
y 0.3573
CCT 4977
Y 11611 Decrease Blue from 151 to 150
x 0.3462
y 0.3572
CCT 4981
Y 11912 Increase Green from 199 to 200
x 0.3462
y 0.3571
CCT 4979
Y 11913 Increase Green from 200 to 201
x 0.3451
y 0.3613
CCT 5034
Y 12114 Decrease Blue from 150 to 149
x 0.3491
y 0.3678
CCT 4918
Y 12015 Decrease Green from 201 to 200
x 0.3499
y 0.3630
CCT 4870
Y 11816 Increase Blue from 149 to 150
x 0.3460
y 0.3574
CCT 4988
Y 117I stopped at step 16.
But this is not what I asked you.
If this device may get D50 without clipping green to 50% gain OSD RGB controls (a big if for a common display) and just happend that you did not find the proper RGB gain combination (this is what we are searching for), it may be caused by OSD RGB gains misbehavior. On my previous note I assumed this for D65, but same apply here:
From *native white point* (RGB gain 100%, after lowering brightnes to target + some big headroom, bigger for D50 target) you start lowering gains. You start from 255, not from you are now.
Then you try to find the minimum GB gain modification that moves native whitepoint to less than X dE radius to target. Lets say 10, 6, 4dE radius…
If after you past the first boundary, moving from one boundary to the next one, *not to your target, just pass the next radius* forces you to push back GB gains waaay down your previous settings, hence destroying brightness more that you’ll want, *don’t do it*. Do not use RGB gains to do this final jump. Such distance, this last step to your actual target (6-4 dE) can be done in GPU VCGT… since it seems that this display on that situation we are describing (moving from radius A to radius B forecs you a HUGE green RGB gain modification) is not capable of doing this kind of jump without messing things.And if moving from native white to less than 10-6dE, I repeat it: not to your D50 target, just getting less than XdE, is forcing you to move G down so much that at 50-70% OSD brightness you cannot get 120nit… then such white is off limits of that display, bc it is forcing you to this abnormal configuration with destroyed contrast & gains.
Third, keep in mind that I use “Black point correction = 100%” under Calibration settings. That is why I get such a relatively “poor” black Luminance. For the work I need to do now, Vincent, that is *fine*. It’s a trade off, right? Remember, my “native” (aka ‘As meaured’) Black chromaticity is blue, like 10,000K blue.
This is solved ot at least improved using RGB offset controls in OSD, if that display has them.
If you aim to D50 white and want some near black white control, then a general purpose monitor (that $1000 43″ is one of those) may not be a good choice.
I’ve used older LED backlit dell ultrasharp widegamut displays aimed towards photography ($450-800 24″-27″), not a general purpose display like yours, and they have OSD RGB offset and do not need to push RGB gains way down 80% for get paper whte in D55-50 range.********
TLDR;
As explained before try to check the boundary where RGB gain controls starts destroying so much brightness, way before reaching desired white, *if it exists*.
If it exists and it is caused by RGB gain misbehavior after you pass some 10-6-4 dE radius to target, try to use VCGT GPU to get that last jump to your deired white, like in a laptop… since RGB gains control cannot do it properly.
If it does not exists, if to get around 6dE to D58, D55 has forced you to move GB waay down so at 100% OSD brightness (350nit native) you are getting 120nit, then such white is off limits of a common general purpose monitor.Vincent,
You wrote :
This is solved ot at least improved using RGB offset controls in OSD, if that display has them.
Obviously, this Dell U4326Q does *not* have “RGB offset controls in OSD”. I wish it had them…
Also, you wrote:
If you aim to D50 white and want some near black white control, then a general purpose monitor (that $1000 43″ is one of those) may not be a good choice.
Remember my NEC PA270 I used for years? With my loss of eyesight (aging and other factors), this screen size became too “small” for every day use. I looked at 32″ offers like the NEC PA301 which I used at Transcon, and some 32″ ASUS / BenQ but those were still too “small” for my eyesight. The best compromise I could find was this 43″ Dell.
Dear Wire,
You wrote :
Of course, targeting a specific xy is unambiguous, but xy measures is utterly non-intuitive numerically.
Not at all! xy numbers are perfectly meaningful for me 🙂
I think that some Benq in PD series for 32″ (P3) may offer this while keeping affordable price (no UC, no HW cal).
Edit: just checked PD3225U, its manual says no RGB offset 🙁Regarding the Dell, as sais before, try to find if RGB gains are misbehaving past some % value, old U2410/PA246Q where known for that.
If it misbehaves but just before that limit you get somewhere 10-6-4dE close to your target => last step for whitepoint done in GPU VCGT.
If it is not misbehaving (if it has some predictable behavior from native to near D50) but it still drops brightness from 350 to 120 when you drop G gain… bad newsI will take a look at “CDT”.
For the record, as I was adjusting xy chromaticities numerically with the help of my trusty, old Minolta CS-200, as I was iterating / agonizing over hitting the exact 0.3457 0.3585 D50 spot, I saw my monitor white suddenly becoming “green”? Yes, “greenish”?
That y adjustment is very sensitive, at least to my eyes.Glad the final xy combination did NOT yield a “greenish” white appearance.
What a relief!Vincent,
The next time I revisit my monitor White point adjustment, I promise I will start “fresh” and follow your suggestions of putting all the gains at maximum, and experiment with lowering G and B down until I hit my desired chromaticities.
I will take a look at “CDT”.
For the record, as I was adjusting xy chromaticities numerically with the help of my trusty, old Minolta CS-200, as I was iterating / agonizing over hitting the exact 0.3457 0.3585 D50 spot, I saw my monitor white suddenly becoming “green”? Yes, “greenish”?
That y adjustment is very sensitive, at least to my eyes.Glad the final xy combination did NOT yield a “greenish” white appearance.
What a relief!That description looks like RGB gains misbehaving past some value.
Obviously, this Dell U4326Q does *not* have “RGB offset controls in OSD”. I wish it had them…
The offset control has been eliminated because it’s about CRT tech and it’s not practical for an LCD to simulate the control. If the designers can’t keep grey tracking correct with simple RGB gain controls, getting an RGB offset control simulation to work properly is even harder!
The RGB offset controls only ever existed because old video technicians expected to find them, not because they made sense for the newer technology.
Programmable display LUTs or VCGT are the right places to handle grey tracking.
Would you find the suggestion to use “calibration curves” to get the desired chromaticities out of a monitor like mine? I guess you would say “it depends what the starting point is”.
I just don’t see why I could NOT try to dial D50 chromaticities myself on the OSD?
Obviously, this Dell U4326Q does *not* have “RGB offset controls in OSD”. I wish it had them…
The offset control has been eliminated because it’s about CRT tech and it’s not practical for an LCD to simulate the control. If the designers can’t keep grey tracking correct with simple RGB gain controls, getting an RGB offset control simulation to work properly is even harder!
The RGB offset controls only ever existed because old video technicians expected to find them, not because they made sense for the newer technology.
Programmable display LUTs or VCGT are the right places to handle grey tracking.
it’s like a cheap version of 2 point control in TVs, this 2nd “gain” for dark greys. Now they offer 10-20 point control in TV even on models without HW cal but this is missing in monitors without HW cal.
I won’t ming that general purpose monitors offer 20-10-2 point controls instead of 1 (RGB gains). It will help with all these problems in Wayland that uers are reporting here were no VCGT is available…. but for common montors they just offer one (RGB gain)Would you find the suggestion to use “calibration curves” to get the desired chromaticities out of a monitor like mine? I guess you would say “it depends what the starting point is”.
Yes, but I have not said to do the full jump from native whitepoint to D50 in VCGT. Not even close.
I’ve said jus to the final approach to D50 in VCGT when your tweaked whiteopoint is around 10-6dE in 5800-5500 range maybe.
This would be an hybrid RGB gain – VCGT approach.I just don’t see why I could NOT try to dial D50 chromaticities myself on the OSD?
You can try the full journey from native to D50, but … do you really do not find strange that you had to push down G so much that at 100% brightness (350nit) you got about 120nit?
Other dells (higher end than this one but on affordable side, manual cal on OSD, 2013 series) do not struggle so much with RGB gains, hence the importance to find if there is a value in RGB gain controls when they go wild (like in 2010 widegamut models), when brightness drops at higher pace or other misbehavior happens.
IF this happens it may be wise to do not push gains into de wild behavior zone bc you get what you have know. Just modify gains to get closer to target white but “outside” the wild zone.I am glad you cleared up the “Starting point” issue. I was under the impression that you advocated using calibration curves to get to the desired white point chromaticities alone, without the intervention of any “hardware” calibration — would you agree to this terminology, btw?
350 cd/m2 is way excessive for my applications, Vincent. The first time I ran into 350 cd/m2 was on an Apple Cinema Display 10 years ago. I thought that was “brutal” but then again, it was using right next to a window, in almost “broad daylight”.
In the end, EVEN if I find a G+B gain combination that preserve much of the original brightness on this monitor, do you really think I am going to “keep” whatever resulting Luminance level that way?
Right now, there is 21 Lux illuminance falling on my screen from the window behind me while the monitor Luminance is 118 cd/m2 : why would you want me to push the Luminance further up? To get the “best” contrast ratio?
