Originally Posted by Chris Corcoran
I have a very very beginner question for you all I have an blue ray calibration disc with color filters and it works amazingly well, and I feel I have a good eye for details when calibrating.
4k and HDR is brand new to me. I just got a new 4k HDR projector, an epson 5050ub and want to calibrate this.
Why cant I use my old disc for hdr ?
If this disc has no filter, how can I accurately adjust the colors, tiny, greyscale etc? Does it have all the patterns needed that can without a doubt allow to me calibrate relatively accurately? Or is it very basic and I need a pro calibration for uhd 4k HDR?
In order to calibrate HDR, you need to put the display into HDR mode. You can calibrate UHD SDR with an HD SDR calibration (Your current) disc.
As far as a blue filter, we have not found a blue filter that works across multiple displays, especially in HDR. We have purchased all of the filters we could find, including $80 glass filters and none of them work. e.g. The filter we shipped in the 2nd edition will work on an LG OLED if you have four layers of the material. On a Sony Z9D, even with 8 layers, it still does not work.
All of the calibration discs use the same Tokyo Blue filter material. Joe Kane used two layers, THX and AVIA used one layer. We have both one and two layers that fold to make three layers. Blue is the most likely to work. Green may work and red almost never works. Green and red are more useful for checking color decoding.
A filter like red, green or blue is only used to set the color and tint control, which really just adjust the color decoder. This is the block that converts YCbCr, from disc, to RGB. With a CRT you had drift and so this control was used to compensate for the analog circuitry. A modern digital display does not drift, so you don't need color or tint. These controls should actually be removed from modern displays. It is either right or wrong. And if it is wrong, it is wrong on purpose.
The only thing that will truly work is a blue only mode built into the display. And then, it must be done in the correct spot in the image pipeline. (closest to the panel) Samsung includes this and LG used to include it. Hoping LG will bring it back in 2020. Sony does not include one, wish they would start. The good news is that Samsung, LG, Sony and others are all correct by default and don't need to be touched in their cinema/movie/theater mode. To be clear, I don't want the color filter mode to set color and tint as they are correct, I want the mode to confirm color decoding is correct. Meaning, are they using the correct math. This requires a green and red only mode. It is this math were they introduce an error on purpose. (and sometimes not) It is a really simple 3x3 matrix. (Think back to your linear algebra class, who said algebra is not used in the real world!
A filter does not let you adjust the gamut of the display, which is the real color adjustment. The gamut, along with grayscale, requires a colorimeter and software in conjunction with test patterns.
You have what I would call video setup. Brightness, contrast, color & tint and sharpness. Then you have video calibration, which is your CMS or grayscale (multi-point). CMS works if the display technology is linear like DLP but does not work on Plasma because it is not linear. The next level of calibration is the use of 1D and 3D LUTs. A 3D LUT is a must if your display is not linear. And the more points the better. In fact, HDR needs more points than SDR does. Disney presented a nice paper at SMPTE last year showing size of LUT as well as LUT algorithm. e.g. A trilinear LUT needs more points than a Tetrahedral does for the same quality.
Video setup you can do with test patterns and your eyes while video calibration requires the colorimeter and software.
With HDR, you have more complexity because of tone and gamut mapping. All HDR displays employ tone mapping. Some HDR displays perform gamut mapping while most simply let the gamut clip. The MadVR Envy allows you to perform gamut mapping. LG is the only company that lets you adjust a 1D and 3D LUT in display. For others, you need to use an external LUT box. For example, in my kitchen (yes, kitchen) I have an XB1 -> 3D LUT box -> 24" VIZIO.
Sorry for going off into the weeds.
We have sent blue filters to those that request them as long as they have provided proof of purchase. You would be surprised at how often people who pirate the disc ask for blue filters or maybe not.
Most manufacturers perform a factory calibration during manufacturing. The problem is panel variance, which is why most see an improvement when calibrating at home. Its also best to get at least 100 hours of use on your TV before you spend money on a calibration. A projector should be re-calibrated when you swap out the bulb.
And as I always say, if you are considering buying the disc, please read the 3rd edition articles on our website first. Make sure you are comfortable and know the limitations.