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My question was more meant in a way, if it could be that DisplayCAL asks me in the calibration step to adjust luminance to 130 but then calibrates to the white point of the display which obviously was at 180.
And then, being at 130 still, not showing the dark shadows since it calibrated to a higher luminance.
I am just wanting to make sure, that I understand better what’s going on, even if I am quite happy now with the results I get.
Thanks for the great support and the app itself, Florian!
Its really fun diggin deep in all that stuff!
If you haven’t set a luminance target on the calibration tab, the initial luminance during interactive adjustment is just what it happens to be when you start measurements.
Hi Florian,
Sorry for warming up that old thread again but I am still wondering about the reddish tint we talked two years ago.
I recently purchased a media light led bulb with 6500k and a cri of 98. When I put my X-Rite white board next to my display the reddish tint is really viewable. The measured white point of the display is much closer to the white on the board under this light. Do you have a explanation for that? Still trying to understand all the related stuff.
Thanks a lot and all the best,
Jonas
I recently purchased a media light led bulb with 6500k and a cri of 98.
You can’t compare to a refernce if that light source is not a reference at all. Command line “spotread -a” on ArgyllCMS folder and trusting i1d3 ambient sensor on that LED (which may not be the most appropiate) check if it is actually white. Actual test should be done that way but with an i1Pro2 or better -a -H.
Calibrite Display Pro HL on Amazon
Disclosure: As an Amazon Associate I earn from qualifying purchases.Hi Vincent,
Thanks a lot for the fast reply! If I understood correctly what you meant with the proposed method I can find out if the LED has the color temperature that was written in the specs, right? I set up my i1 Display Pro with the ambient light cap on around 40 cm away from the bulb on my desk. The readings I get are:
Unable to apply FWA compensation because it wasn’t set up
Result is XYZ: 544.811969 576.412159 627.355925, D50 Lab: 191.986765 -5.935584 -34.710584
Ambient = 576.4 Lux, CCT = 6560K (Duv 0.0041)
Suggested EV @ ISO100 for 576.4 Lux incident light = 7.8
Closest Planckian temperature = 6349K (DE2K 5.5)
Closest Daylight temperature = 6517K (DE2K 1.3)
When I interpret these data correctly this is pretty close, right?
I wrote earlier that the measured white of the display is much closer to the x-rite white board lighted by that media light bulb than the d65 calibrated white. Maybe my perception was fooled by the white wall in the back of my display which is a normal wall color. Actually when I look now I’d say the x-rite board is somewhere in between. The measured white looks more blueish than the x-rite board and the calibrated white looks more reddish.
I think my most important question is: can I trust my calibration?
All the best,
Jonas
Measure display white with WLED PFS CCSS correction for mac displays. Then calculate actual distance between (supposed, becacuse BULB has to be measured with an spectrophotometer) LED bulb white and display white.
LED bulb and display can be < X dE to target but actual distance between bulb and display as point can be twice, like points in a circle.
As you move up or down mac brightness white can drift as in any other monitor. When you calibrate it, it was OK but with auto brightness or because you change it it may be no longed at calibrated values. Sice it may be not practical to have a laptop at the same brigtness setting all the time, because you can move it to another room, it is something you have to live with. Maybe measuring white at 25-50-75-100% brightness, find a mean place of drift and when calibrate use that brightness setting and asume there will be a drift if you move from that setting, but that dift would be the less possible.
Also i1d3 + CCSS (for mac or any other display) relies on that colorimeter actual spectral sensivity curves and spectral sensivity curves in firmware match. This usually holds for all well preserved i1d3 but may add some little dE uncertain. When apply the same “circle” approach you may see a color cast against something close to reference but that it is not a “reference” (0 error), Display is < A dE to true reference, bulb is < B dE to reference. A and B are low. Distance between them can be twice.
The last issue is “observer metameric failure”, *you* and std observer CIE 1931 2degree do not match on certain wavelength regions (expected) but WLED PFS backlight have very concentated high spikes in a very narrow bandwith in red wavelengths. If by age or genetic chance you and std observer drift a litlle more in those wavelegths, so even with a perfect measurement device you’ll see a color cast.
If that happens :
-live with it, it’s just a whitepoint drft and vision adapts
-use visual whitepoint to get a match
whatever fits you better.Dear Vincent, thank you again for your detailed response! I am beginning to understand the concepts behind much better!
Yuji notes CRI ~90 for crimson color etc., total CRI is summary. Dimmable LEDs have CRI 98 at warm edge only. All consumer high-CRI cool LEDs have fall in violet and crimson, some fall in cyan. I’m not sure if metamerism effect may appear between 6500K natural light and fine made display (with RGB spectrum curves close to normative for daylight perception), but your LED’s aren’t perfect. Beware also of TLCI index for shooting.
Thanks.. I thought the LEDs might be More reliable since they are sold by Flanders but probably it’s not possible yet to build better LEDs..
Thanks.. I thought the LEDs might be More reliable since they are sold by Flanders but probably it’s not possible yet to build better LEDs..
They can… but you need more than CRI to verify it. Vendor may “hack” CRI score like VW in diesel-gate but overall color render is poor. There are other scores less “hackeable”.
You need spectral power distribution (ebergy per wabelegth) to properly verify how good a light source is, maybe vendor provides it.For example
Complete LED Color Rendering Database of 2018: CRI, TLCI, CQS, TM30-15
I couldn’t find it in the database. it’s this one.
Seems fine … for an white LED, from your link:
Reflects too much blue, too few cyan as Alexei explained. But for a WLED looks very good. I mean, Blue led + yellow phosphor has this kind of issues by design, but looks minimized.
For less bumpy and more daylight white you’ll need to move to multiled or violetled+RGBphoshor like Yuji VTC
I mean… this kind of stuff is important because light sources are used to light objects that have to REFLECT light, instead of going to your eyes directly.
On displays it does not matter since it goes to your eyes and weighted by a tristumulus observer, so same color can be obtained with a variety of led backlights or CCFL
Thank you so much for taking the time to explain all that stuff! I really appreciate it!
So I guess also the lamp is important.. the bulb is mounted to an Artemide Tolomeo with a silver Alu screen.. this might change the spectrum as well..
Thank you so much for taking the time to explain all that stuff! I really appreciate it!
So I guess also the lamp is important.. the bulb is mounted to an Artemide Tolomeo with a silver Alu screen.. this might change the spectrum as well..
Depending on what you want to do. A good WLED may fit your needs for ambient light. These other more exotic LEDs with spectral powrer distribution closer to daylight at different CCT are meant to be used in more color critical applications as normalized light source for printed copy comparison, or high end equipment for film.
Also it depends on how much ouput light power you need, it may be easier to get huge light output with some tech than with other. That LED database is a good start.
