Why Calibrate Dynamic Mode?
Dynamic Mode on the Epson TW9400 / UB6050 / 5050 has a lot more aggressive dynamic iris than on the other modes. What this means is the following
- The iris will clamp down harder during dark scenes
- The iris actually has a range below the lowest position in the other modes creating more contrast
- The iris will clamp down to its lowest position during a fade to black and eliminate almost all light (not quite but low enough that your pupils will need a lot more time to adjust than in other picture modes)
Aims of the Calibration
I wanted to create a calibration that could be used for both SDR and HDR without having to switch picture modes – or load a new memory. What’s more, I wanted the gamma controls to be usable to switch between 2.2, 2.3 and 2.4 gamma (0, -1, -2 settings on the Epson).
To achieve this, I needed to have the following:
- Greyscale and Gamma as accurate as possible for SDR and HDR without using the custom gamma controls
- SDR gamut that was as accurate as possible and then let the Epson tone map to the HDR gamut which it does quite well – HDR gamut not as much a priority however.
- If possible, have the calibration be accurate for both medium and high lamp (this is always a tall order but wanted to measure the errors regardless)
- The resulting calibration is accurate for SDR without any visible errors (apart from 100% blue, 100% yellow and 100% red).
- The resulting calibration has accurate greyscale and gamma in both medium and high lamp with the same settings
- The gamma is flat without using the custom gamma controls. Instead the greyscale controls were used to dial in the gamma and allow the use of the normal gamma controls.
With regards to HDR:
- The resulting calibration is accurate for HDR greyscale and gamma – as the Epson uses the SDR gamma to tone map.
- With the Epson doing the gamut translation, the BT2020/P3 gamut is not going to be as accurate as doing a dedicated HDR calibration but it looks visually accurate when compared to a calibrated HDR Natural picture mode. The errors are a bit higher however – between 2 and 6 – as opposed to 0 and 3 for deltaE.
I try and avoid using the offsets when calibrating greyscale on the Epson as anything other than defaults compromise the near-black gamma for one or two colour channels without any controls to be able to correct them. Unfortunately, this is not a JVC where auto-calibration takes care of the internal mapping tables and corrects for these issues. I was able to avoid using them however.
Visual inspection of the calibration shows excellent colours and gamma response that stays accurate when switching between lamp modes.
Graphs and numbers confirm the accuracy seen in SDR – and HDR in fact. The only thing left to measure will be the HDR gamut, however it looks visually as good as the Epson is capable of without its P3 filter.
The gamma controls allow for switching between 2.2 gamma for brighter rooms (0 setting) and 2.4 gamma for home theatre type environments (-2 setting).
Medium Lamp Gamma and Greyscale:
High lamp Gamma and Greyscale:
BT.709 Gamut Before and After – Medium Lamp
All targets under 75% are under the visible threshold of 3 so no concerns here. 100% targets line up pretty well also, except for blue which is way too bright (you can’t see luminance on this diagram). Red and Green 100% are less of a concern.
Could this be improved even further? It is entirely possible. However, more accuracy would require a lot more time and it is unlikely to result in visible differences when viewing normal content. It is worth exploring as the lamp ages – and drifts less. Spending so much time getting things 100% aligned when the lamp is still new and shifts is not worth the effort.
P3 within BT.2020 Container Gamut – Before and After – High Lamp
While the BT2020/P3 gamut that Epson tone maps once SDR gamut is calibrated isn’t as accurate as a dedicated HDR calibration, it is still within the visible threshold of 6 for targets below 75% saturation, except for green – and lots of the points do line up under threshold of 3. However, green is not going to improve without the filter in place. What is good however, is that cyan is corrected, which had the most detrimental effect on image quality out of the box and most colours are pulled closer to their targets. In normal viewing the errors are not obvious and will do for an evening binge around Netflix or Disney+ without having to keep loading memories or switching picture modes. Job done!
P3 within BT.2020 Container Gamut – Natural and Digital Cinema Out Of the Box
For reference, I wanted to post what the HDR gamut looks like for Natural and Digital Cinema Picture Modes out of the box. Natural picture mode lines up pretty well, but Digital Cinema could use some work, and is worse in some areas than our SDR to HDR gamut mapping.
Lamp Hours: 35hrs, Screen type used: 0.9 gain – no colour push
Colour Temp: 7
Skin Tone: 3
Lamp mode: Medium or High (e.g. use Medium for SDR and High for HDR but either works for both)
Dynamic Iris: High Speed
Custom Colour Temp
Offset R: 50, Offset G: 50, Offset B: 50
Gain R: 50, Gain G: 40, Gain B: 50
Editing Calibration for Your Unit or Older Lamps
Please note that there is variation between units, lamps and especially as the lamps age. It is only really possible to ensure your unit is accurate by calibrating it yourself – or having it professionally calibrate.
HOWEVER, if you find that the picture is not looking great (e.g. too red, too blue or too green), you can adjust the Custom Colour Temp controls to let more light through as follows:
Picture is too red: Either reduce red or increase green and blue.
Picture is too green: reduce green even further (unlikely scenario however)
Picture is too blue: Reduce blue
This is a rather simplistic way to troubleshoot this, but in absence of having your unit calibrated, this may be your best option. Otherwise, if things are not looking great, use the Natural picture mode on your unit.