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I’m new to displayCAL but not new to color calibration. Just started with displayCAL, migrating from i1 Profiler product supplied software. I feel like I opened up Pandora’s box! Good job on the software. I have some questions in looking at a 2 year old Dell P2715Q 4K UHD display on my MacBook Pro (MBP) 2017. It is attached straight through via USB-C port from MBP. Mostly I operate in closed cover mode with two 4K displays.
My findings:
- Light levels. It seems like the display default brightness level is 160 nits. I think this may be a bit too much for one monitor to handle. I see a significant amount of clipping in full white screen – with a gray scale after monitor setting in all default values is complete, visually I see the white portion as red while the remaining gray scale is good. I manually reduced the (hardware drive) off from 100 to 89%, and visually rebalanced the custom color RGB settings and this problem goes away. It is a two year old display and I fear that I am over-driving the screen! What are your suggestions and how do I get there in the settings of the drives and balancing the colorimetry from there.
- I want to match the brightness and colorimetry to my newer Dell model screen – a U2718Q. What results should I expect?
- How close a match can I expect to achieve to the two? I’m using the later model Dell for critical photo processing. What would you like to see to determine if there is a best match. Visually now, after my manual overriding adjustment, it’s pretty good. I’d like to put a number to it and improve it some more.
It is a two year old display and I fear that I am over-driving the screen!
Typically there is no way to “over-drive” a digital display that can cause actual harm to the display. The only thing that over-driving one or more of the red, green or blue channels will do is introduce color casts (a well designed display will not allow adjustments that push any of its channels too far, but some manufacturers seem to cut corners at every occasion and save on properly designed circuitry…)
Operating the backlight at high brightness levels will reduce the backlight lifespan somewhat – white LEDs which are typically used for backlighting are actually blue with a yellow coating, which deteriorates slowly over time (years). But 160 cd/m2 shouldn’t overly taxing for a modern display. Most of them are rated at 300 cd/m2 peak light output or more.
Of more concern is that the monitor light output should be suitable for the ambient lighting situation to reduce eye strain – a too dark monitor in a bright environment, or a too bright monitor in a dark environment should be avoided.
I want to match the brightness and colorimetry to my newer Dell model screen – a U2718Q. What results should I expect?
How close a match can I expect to achieve to the two?
I do not know how close these two screens are in effective gamut, so you’ll have to see yourself.
It is a two year old display and I fear that I am over-driving the screen!
Typically there is no way to “over-drive” a digital display that can cause actual harm to the display. The only thing that over-driving one or more of the red, green or blue channels will do is introduce color casts (a well designed display will not allow adjustments that push any of its channels too far, but some manufacturers seem to cut corners at every occasion and save on properly designed circuitry…)
Operating the backlight at high brightness levels will reduce the backlight lifespan somewhat – white LEDs which are typically used for backlighting are actually blue with a yellow coating, which deteriorates slowly over time (years). But 160 cd/m2 shouldn’t overly taxing for a modern display. Most of them are rated at 300 cd/m2 peak light output or more.
Of more concern is that the monitor light output should be suitable for the ambient lighting situation to reduce eye strain – a too dark monitor in a bright environment, or a too bright monitor in a dark environment should be avoided.
I want to match the brightness and colorimetry to my newer Dell model screen – a U2718Q. What results should I expect?
How close a match can I expect to achieve to the two?
I do not know how close these two screens are in effective gamut, so you’ll have to see yourself.
Thanks, Florian, for your answers to the questions in my post. I typically have a light level set that matches ambient light pretty well at 160cd/m2 (much better than 120 level previously/recommended by i1 calibration software and some others), so I am loathe to change it. These are both “modern displays” so I’m going for that.
One thing I’m noticing in overall gamut result (graph) on any monitor is at the lowest measure of brightness (1-5%), no screen is linear, of three that I profiled. Why?
One monitor (the P2715Q) did not match the upper range of gamut (90-100%), being out badly there. I found that the monitor’s driver level setting was being badly overdriven at “default monitor” (one channel @100%) setting so I decreased it to avoid that distortion and matched the driver set for the other two to a lower point. You could easily see the reddish clipping on a full white screen near the center of the image of a full white section.
One question that came up doing the initial calibration profile is setting the contrast. I learned to leave contrast at 100% setting and adjust brightness to achieve the starting point in DisplayCAL. Is this correct? I don’t see anything in the documentation or on screen instruction about this. It seems to have worked out great in profiling the display.
One thing I’m noticing in overall gamut result (graph) on any monitor is at the lowest measure of brightness (1-5%), no screen is linear, of three that I profiled. Why?
The black of many LCD screens is usually either bluish, violet, or greenish. The only way to correct the black point hue is to add red, green, and blue – this reduces contrast. Usually the black point being another hue is not a problem though as you won’t strongly perceive it in the vast majority of occasions (unless viewing an actual full black screen).
One question that came up doing the initial calibration profile is setting the contrast. I learned to leave contrast at 100% setting and adjust brightness to achieve the starting point in DisplayCAL. Is this correct?
For most LCD computer monitors, “contrast” should be left at default. This is actually mentioned in the documentation.
