8 Jul ’22
- More details on HCFR settings under greyscale and at the end of article
I thought I’d share the process by which you can calibrate the Epson UB6050 / UB5050 / TW9400 / TW8400 for HDR.
Step 1. Greyscale / White Balance Calibration (SDR)
Epson’s tone mapping is based on the unit being calibrated in SDR mode. So the best baseline you can give it is to calibrate a picture mode for greyscale / white balance using SDR patterns.
It is a good idea to only touch the gain controls for the two-point white balance then move onto the multi-point greyscale and work down the steps using the on-board controls.
The reason why it’s not a good idea to touch the offset controls is because they affect near-black gamma in a way that’s not correctable. That’s not such an issue on a TV but on a contrast-limited projector, it can affect shadow detail. Of course it’s not always possible especially if a picture mode is way out of whack and the multi-step controls don’t respond. However, this isn’t really an issue on these lamp based Epsons (as opposed to the LS12000 in dynamic mode which is a bit of a problem still – hoping for a firmware update there but if you have a few days it is doable there too).
Update 8 Jul ’22
Be mindful that Epson’s onboard multi-step greyscale control has 8 steps. However, when it comes to HCFR, it is considered a 7-step greyscale. This is why you need to configure HCFR in its parameters for a 7-step greyscale when working on the multi-step greyscale controls. (See screenshots below. It’s a gallery so you will have to click on them.)
The above is especially critical if you decide to do gamma using the multi-step greyscale controls, in which case you MUST disable the Epson’s onboard pattern generator. To do this, you go into the multi-step greyscale and you press Enter on the Epson’s remote control. This will disable the internal pattern. To check that it is disabled while you have an HCFR pattern up, you can go down to level 7 on the Epson’s controls for example. If the pattern changes on the Epson, it means you have not disabled the onboard patterns. If it doesn’t change, that means you are still displaying your HCFR pattern.
Step 2. Gamma (SDR)
The next step I would do is calibrate gamma to power law 2.2 using the multi-point greyscale controls with the Epson’s gamma setting being on 0.
Yes, using the multi-point greyscale is an option and works really well on these Epsons. The reason this is a good idea is that you get to keep the option of changing the gamma based on your viewing conditions without having to calibrate a new gamma calibration using the quite fiddly gamma controls.
The Epson’s HDR tone mapping is based on a Power Law gamma 2.2 being calibrated in gamma position 0, at this the EOTF lines up perfectly. at all the HDR slider positions.
Step 3. EOTF (HDR) – Optional
However, you can calibrate a brighter HDR10 EOTF using the gamma controls. This is what I did for this article. This is a good option if you have a larger screen and you would like to retain more of the slider options as usable for your setup. As you increase the HDR slider, the Epson will crush more and more of the highlight.
Update 8 Jul ’22 If you are calibrating your EOTF (or even SDR gamma) using the gamma controls, which you should be, you should do a 10-step greyscale in HCFR, which will get you a 10-step luminance measurement as well. This lines up better with the gamma controls than the 7-step greyscale we did earlier.
So one option here would be to measure your EOTF on slider position 8. You will need to use the nits value you measure for 50% stimulus – which is your reference white or diffuse white in HDR – and then up it by an amount of your choosing. For example, if you measure 15nits here, you may want to up it to 20nits, and then create an HDR10 EOTF curve based on that new diffuse white value. This is quite easy in HCFR as you simply enter the new target diffuse white to scale your target curve.
Once calibrated, the rest of the slider values will line up but will be brighter.
Step 4. Colour Management System (HDR)
The final step is calibrating the CMS. Now clearly, this needs to be done in HDR mode. If you are using patterns from HCFR, you need to have your output in SDR RGB mode and then force the Epson into HDR mode. But make sure you do not output HDR from your PC or laptop as that will mess up the patterns. The only thing you need to make sure of is that HCFR is set for REC.2020/P3 and HDR10 gamma (ST.2084 EOTF) just as in step 3.
HCFR will scale the patterns to be at diffuse white, which is the correct way to calibrate the CMS for HDR, especially on a projector with limited luminance.
If you are using external patterns, then make sure those patterns are at 100nits and not at a 1000nits because most of the content is around 100nits even in HDR so it is important to prioritise that, as opposed to calibrating for highlights.
The Epsons are not able to reach full P3 gamut unless in Digital Cinema Mode but this should not discourage you.
If you want to retain the full use of the HDR tone mapping slider, you may want to do CMS calibration with the slider between 6 and 8 (8 is probably the best spot). If you want a more accurate calibration and use one slider position, then calibrate CMS in the slider position you will use the most. The calibrations I have shared with you on this site were done so the HDR slider is usable across its full range.
Alternatives to the Above Process
To be really pedantic, and to do this by the book, you should calibrate greyscale in HDR mode after you went through it in SDR mode. That way you know that everything lines up properly in HDR as well. My experience with this however, is that as long as the greyscale is ruler flat in SDR on the Epson, it isn’t really a problem in HDR mode either.
But this isn’t the case on most displays, so while I put this as an option for the Epson, it isn’t necessarily a good habit to get into and you shouldn’t’ really skip this step. However, if you are just learning calibration, the Epson is an easy unit to start with as it’s relatively linear once SDR is calibrated.
However, to check the greyscale in HDR, you can’t really use the onboard patterns. You must force the unit into HDR mode and use external patterns – preferably autogenerated from HCFR. Also, the greyscale steps won’t necessarily line up as expected anymore so you will need to figure out which stimulus levels are impacted by which control. There is a process I included in The Display Calibration Guide for this.
An additional complication – as I said before – is that Epson used an 8-point greyscale for these units. This is really a 7-point greyscale in HCFR (as black is considered level 0 in HCFR which is not part of the greyscale step numbers, while on the Epson it is Level 1 and forms part of the number of steps).
However, if you are just leaning calibration, as you get more confident you should really try to do the full workflow in HDR from greyscale to EOTF to CMS. The only thing to keep in mind is that your results may not be as compatible with Epson’s HDR tone mapping slider if you deviate too much from what the Epson is expecting.
Which Picture Mode?
Which picture mode should you calibrate?
- Natural mode is the most balanced in terms of light output and accuracy.
- If you wanted a mode you can easily switch to without having picture memories, you could try Bright Cinema. However, bright cinema has jacked up contrast in its internal tables, so you must start with setting White and Black Level before you start calibrating. This is a good habit to get into in all cases, btw, but not as critical for the other picture modes such as Natural or Digital Cinema.
- Dynamic mode has a lot more light output and the dynamic iris is a lot more aggressive. However, this can annoy some people. If you want an example of a dynamic calibration that reduces iris pumping then look here.
- Digital Cinema mode reaches the full P3 gamut, but it has reduced light output and the colours might not agree with everyone. I find this colour mode a bit difficult to watch actually as the colour filter is not transparent. (Could be observer metameric failure – that is a difference in colour vision compared to a standard observer so your mileage may vary.)
A few more things for configuring HCFR:
- For SDR, you need to select REC709 and a 7-step greyscale as discussed before. If you are calibrating using the custom gamma controls, you need to switch back to a 10-step greyscale for gamma / EOTF calibration
- For HDR, you need to select BT2020/P3 and the ST.2084 gamma option. You measure your diffuse white at 50% stimulus on a 10-step greyscale and your target luminance at 100% stimulus.
- HCFR pattern generation generally needs to be in the 0 – 255 setting (there are exceptions which are detailed in the Display Calibration Guide).
How to Learn Calibration
Refer to this article about what you need to start calibrating a projector.
However, there ARE some free guides online you can start out with of course. I just hope the above article encourages you to start the learning process.
Some of the free content is linked from the HCFR thread over at AVSForum. Please note that I can’t really offer support for the free guides as it is not my content and I don’t find it comprehensive enough to be frustration-free. You will need to seek help in the forums for those. Thank you for your understanding.