What determines the highlight handling?

D

DanHD

Well-known member
I've been wondering, what components/specs/compression techniques in pro cams have the most effect on how that particular cam presents hot spots/highlights?


I've seen comparison footage from my hpx500 against a hpx2000 with AVC intra onboard and the difference in the highlights is incredible. the 2000 doesn't render hot spots as harsh, ugly blotches of white, but rather retains alot of detail in the highlights


Is this because of the bit depth of AVC intra, providing for a more precise tonal gradation? or perhaps the size of the pixels? or the A/D converter?

Why do highlights specifically look uglier as cameras get cheaper?
 
DanHD said:
I've been wondering, what components/specs/compression techniques in pro cams have the most effect on how that particular cam presents hot spots/highlights?


I've seen comparison footage from my hpx500 against a hpx2000 with AVC intra onboard and the difference in the highlights is incredible. the 2000 doesn't render hot spots as harsh, ugly blotches of white, but rather retains alot of detail in the highlights


Is this because of the bit depth of AVC intra, providing for a more precise tonal gradation? or perhaps the size of the pixels? or the A/D converter?

Why do highlights specifically look uglier as cameras get cheaper?
Click to expand...

Not knowing exactly the details of these cameras, and compression techniques... in general yes bit depth plays a significant role in recording the values in a scene... Artifacts of limited bit depth are banding lines in areas of gradations, and the 'saturation' of high values, as in the case of lights in the the shot.

Basically, if one is trying to put 12 bits into 8... something gets lost...
 
DanHD said:
So bit depth only?
Click to expand...

There may be also an effect of attempting to put higher density on a limited sized chip... the idea is that one gets 'band broadening' when one attempts to 'narrow down' the observation interval.

The result would be that at a 'far' distance, a 'point source' like a street lamp would look 'smeared', so both effects combind would give a blob of one intensity value...
 
It could also do with the knee settings; if you're using cine-D on the HPX170 then there is no rolloff of highlights at all. Try HD NORM with a knee of LOW and see if you like the highlight handling better.
 
dynamic range (lack of) is the culprit

most natural scenes exhibit more contrast/latitude than most video cameras can capture.

If you can't control the light, you have a choice: crush the blacks, or blow out the highs. Tweaking knee and pedestal etc will help retain more detail in the upper and lower extremes of the luminance range, but the choice still has to be made - you cannot fit a quart of water in a pint jug.

- film cameras generally have more dynamic range than digital, bigger CCDs have more dynamic range than smaller ones.
 
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