This year JVC has introduced Auto Tone Mapping which automatically adjusts the projector’s HDR settings (tone mapping) to try to optimize HDR10 image quality. The goal is to better utilize the NX7’s brightness capabilities based on the image on screen. The NX-7 uses the static HDR metadata to make tone mapping adjustments. The two pieces of metadata that the projector’s video processor uses for HDR tone mapping are:
• MaxFALL (Maximum Frame--Average Light Level) average brightness of the brightest frame in the entire clip. Authoring guidelines state that this should not exceed 400 nits.
• MaxCLL (The Maximum Content Light Level) which is the brightest pixel in the entire clip.
The average brightness of a most HDR video frames are usually much less than 400 nits with a few peak highlights (sparks, flame tips, reflections) reaching up to 10,000 nits.
In many cases the metadata is missing or incorrect so the DLA-NX7 might not have the right information to work with. While NX-7 uses the MaxCLL and MaxFALL metadata should be embedded in the HDR Content, better LCD and OLED TVs actually measure the HDR content frame by frame to generate accurate metadata dynamically. Adding the capability of measuring HDR metadate would further improve the HDR performance of projectors.
Since the embedded static MaxCLL and MaxFALL is applied throughout the entire movie sometimes the tone mapping decisions made by the projector can be a little off.
However since the MaxFALL or MaxCLL metadata is static based on the average brightness of the brightest frame and brightest pixel in the movie, certain scenes with lower than average frame levels can still be way too dark. An example is Stranger Things season 3 episode 7 – in the JVC default setting, the brighter scenes look great, but the darker outdoor night scenes were nearly unwatchable.
The nice thing is you can fine tune the look of HDR to fit your taste by using the Mapping Level adjustment. Sony FPJ has “HDR Contrast” to adjust average screen brightness depending on customers’ environments or preferences as well.
BTW, since HLG is based on a Gamma curve just like SDR, it does not need to be tone mapped by the projector.