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Hi everyone! I’m new to this whole calibration and color management thing. I’d like to start by saying I’m not a professional and do not NEED all of this for a living… I’m mainly doing it because I’m a tech enthusiast and would like to have a (decently) calibrated display. My monitor is an LG 34GL750 (via DisplayPort, don’t know if that matters in some way). It’s my main and only monitor to my desktop, so I use it for basically everything (from gaming – a bit less these days – to movie/show/video watching in general, browsing the web, etc.). Now, I have already done my first calibration with DisplayCAL which I’m using right now and I think it’s pretty good (the actual first one I’ve made with sRGB turned out crap – I think because I set the Whitepoint to “As Measured” or something like that). I’d like to maybe make a few more calibrations now with some adjustments to get more accurate results after I gather some answers to some questions I have, which are as follows:
- This monitor has 4 gamma settings. I’ve watched the Hardware Unboxed tutorial video on calibrating displays and it’s said there to basically reset the monitor settings and disable any kind of enhancement, which I’ve done: in my case, black level stabilizer is set to 0, no energy saving mode is enabled, no motion blur reduction/backlight strobing, ‘tho Freesync is enabled (also have an AMD GPU). The gamma settings on the OSD are just labeled “Mode (1, 2, 3 or 4)”. Modes 1, 2 and 3 are progressively Darker (1 being the brightest and 2 being the default which is selected after reseting the settings). However, in the manual, it’s said that “If it’s not necessary to adjust the gamma settings, choose Mode 4”. So, which should I choose? The “no adjusment” (mode 4) or the one it defaults to after reseting the settings (mode 2)?
- Which whitepoint should I choose? Is D65 the same as 6500k? And is that the same as the sRGB whitepoint? Or should I use As measured? Or am I writing nonsense here? Is this just preference, in my case? 5000k
- What about white level, should I stick to the 80-120cd I see recommended everywhere? Before buying this, I always used my monitor at 50 brightness (also the default after settings “factory reset”) and that is measured to be around 180cd. Is that “too bright”? Should I calibrate it the way it is or is that going to “hurt” the calibration process? Is it better to calibrate at 120cd and then change the brightness after… I assume not, correct? Is it possible for my monitor to be more accurate being less bright (i.e., with the brightness level at around 120 or 100?)?
- Should I use Gamma 2.2, 2.4 or sRGB for the Tone Curve? The displayCAL ReadMe talks about maybe using gamma 2.4 and also using ambient light measurements, that kinda confused me.
- Another ReadMe doubt: “A white point temperature different to that native to the display may limit the maximum brightness possible.” so…? Should I just use “As Measured”?
- What are all the files that DisplayCAL generates? ti1, ti3, bpcti3, b2a1 post clut and postclutsmooth (PNGs?), wrz. What are those for?
1. LG’s gamma modes are weird. Generally mode 2 will be where the factory calibration lives if your monitor has been factory calibrated so the color temp will be different on all the other modes. You can run the calibrated display report on each mode and pick the one that has the gamma closest to what you are going to use.
2. D65 and 6500k are I think the same, sRGB is technically 6504k so slightly different. 5000K should be used if you are doing print matching with a proper lighting booth.
3. Unless you are doing super color critical work and are in a fairly dark room 100-120 nits is a bit dark for most people. Don’t worry about brightness too much, just set to something you like and keep it there after profiling. Also it’s never a good idea to set a brightness target in the software. If you need a specific value use the interactive adjustment step to dial in the brightness using your monitor controls.
4. The sRGB tone curve shouldn’t be used for displays especially if you watch any video. dark portions get significantly brighter and look terrible for video. If your viewing environment is fairly bright then use gamma 2.2 and if it’s fairly dim you can try 2.4 and see if you like it.
5. Doing any adjustments to color temp either through monitor controls or via the VCLUT that the calibration uses will limit the max output of one or more color channels which lowers the max brightness of the display and by extension the contrast ratio. I had an old monitor that the native color temp had drifted so much over the years that too correct it limited the max brightness to about 80 nits and the contrast ratio to about 300:1
6. No idea
2. D65 and 6500k are I think the same, sRGB is technically 6504k so slightly different.
Let me try and correct myself I had forgotten the complicated details.
https://en.wikipedia.org/wiki/Color_temperature
6500k refers to the color temperature of a perfect black-body radiator. D65 (and the others like D55, D50) represent specific color coordinates that are actually slightly different than a perfect black-body radiator as they refer to daylight color temps that are adjusted for atmospheric scattering.
sRGB and most video use D65 for their white point so that should be the ideal setting for your usage.
Is D65 the same as 6500k? And is that the same as the sRGB whitepoint?
The technical answer is:
D65 is a spectral power distribution, i.e. the definition just says how much light there is at each wavelength. To get from that to a “color” in xy chromaticity coordinates, you integrate it with the CIE 1931 2° observer (the “model” of human color perception used for pretty much all display calibration). The result you get is roughly (0.32171, 0.32902), but the exact result depends on how you calculate it. Color space standards like sRGB define their “D65” white point as exactly (0.3127, 0.3290). So, that’s the technically correct thing to calibrate to.
6500K (roughly, it’s actually 6503.51… K) is the correlated color temperature (CCT) of the CIE 1931 xy coordinates of D65. Note how it’s only a one-dimensional quantity and therefore does not actually define a specific color, but rather just how “red” or “blue” a color is. ~6504K on the CIE daylight locus (the default setting in DisplayCAL, need to enable “Show advanced options” to see that though) is another way of defining/calculating the CIE 1931 xy coordinates of D65. But again, technically this is not what you want, as the sRGB standard defines its white point as exact coordinates with 4 decimal digits. The difference is so small that it really won’t matter in practice though. The measurement error of your colorimeter and the drift of your display over time will make a way bigger difference.
Ok, got it! Thanks for all your answers so far. I’d like to know if after I’ve made the calibration, can I uninstall DisplayCAL for the moment? My question is related to the 1D LUT applied to the video card, is that “contained” in the .ICM file that DisplayCAL generates at the end of the process? Is that “all” that I need? Or is displayCal doing something else actively (besides just making sure the correct profile is being applied to the correct screen via the DisplayCAL Profile Loader).
Not sure why you’d want to uninstall it, but yes, your understanding is correct. The profile loader is just there to ensure that the VCGT (1D LUT) data is always loaded into the GPU, and that data is contained in the .icm file along with the profile data.
Basically, because with it installed, sometimes the profile doesn’t get applied (I’m sure it’s a bug with DisplayCAL working with AMD cards or something like that). When I uninstall it, I can force set it via the Windows settings and then it just “stays” applied for most things I care about (remember I don’t use any color managed application like Photoshop or Premiere, just Windows and web browsing mostly).
