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Hi,
having switched my projector to “high lamp mode” in order to use it for BT2020 content, I am not happy anymore with my old setup using “low lamp mode” for Rec709. I always felt it being a little to dim but in compare to the very nice results of Rec2020 in high mode it is not satisfying at all anymore.
The Problem is that plain high mode is way to bright for BT709 content, since it makes use of all the range most of the time, very different than HDR content which keeps a good headroom for highlights.
Can I use “white level” in the calibration tab to lower it? – just type in the right number instead of “as measured”?
If not, is there any other way to trim it down before it is sent to the projector? Firstly I don’t want to change settings on the projector all the time and secondly none of the two settings fits right. I want something between “low lamp” and “high lamp”.
Can I use “white level” in the calibration tab to lower it? – just type in the right number instead of “as measured”?
Yes, but keep in mind that lowering the projector output in this way has drawbacks: It stresses the projector lamp more than necessary, lowering its lifespan, and because the video card output may be limited to 8 bits per channel, it can introduce banding (depending on the graphics card, connection and driver).
Very good!
I see no other option, since low mode is a bit to dark and high mode is quite a bit to high. So the no-compromise-approach here is to compress the signal. I know I will also pay with black level, but the contrast makes up for that.
My graphicscard puts out 12 bits, I just recently bought it just for that. 🙂
So all is fine, thx!
I have something strange to report: I can set the white level to some value and calibrate, profile and create a 3D-LUT and displaycal will show me a very decreased brightness in the preview (when I get offered to install it). Madvr though doesn’t care and give me full brightness. I can see a change in the colors when the LUT gets loaded, so it is actually working.
I do not use “apply calibration” and I guess this will cause the isuue. We had that before and honestly I never uderstood it: Whenever I apply the calibration I get strange colors and solarisation effects. Checking with other people in the kodi forum I figured that this option is applying the calibration twice. It works fine for me without it so far, but I never understood why the option is there.
I do not use “apply calibration” and I guess this will cause the isuue.
Indeed. The luminance reduction is done via the 1D calibration.
Whenever I apply the calibration I get strange colors and solarisation effects.
How much does the calibration reduce the luminance? If it limits the gamut too much, you may run into clipping issues. Please attach the profile.
Checking with other people in the kodi forum I figured that this option is applying the calibration twice.
The only way the calibration can get applied twice is if it’s applied to the 3D LUT and you also install the profile containing the calibration (and thus the OS or profile loader will load the calibration into the graphics card gamma tables). This doesn’t look to be the case for you though because it conflicts with your observation above (luminance is not lowered if you don’t apply calibration to the 3D LUT).
I never understood why the option is there.
If using 1D calibration, the 3D LUT will not give correct results without it. Either the calibration has to be applied to the 3D LUT itself or applied in another way (i.e. via the graphics card gamma tables).
I’ll have to dig out the thread obout the calibration being applied twice and see if I can make sense of it. I will also try to render 3D-LUTs with calibration from the measurements I have and compare to the ones without. And I will attach you the files. All in all it sounds like a weekend job.. 😉
Apart from that I went and calibrated the projector again with low lamp mode and the brightness is just fine for 709 content. At some point I bought a new lamp and kept on using the LUT I made for the old lamp. Strangely the picture is way brighter after have reprofiled it. Seems odd but that’s how it is, all is crisp and clear in low lamp mode for 709 content and I get great dynamics in high mode with Rec2020 content.
Still I want to figure out the issue so I will report back.
So I found some free time and made new LUTs with integrated calibration. The problems I used to have with weird colors are completely gone and the colors look a even bit better than before. Not that much different but calmer, more realistic. It did cost me some brightness though, especially the Rec2020 LUT. I made several with different Display peak luminance and according Mastering display settings, so I can choose depending on the content.
So all in all I happily arrived at HDR land, thx again!
