Chaos Corona Forum
Chaos Corona for 3ds Max => [Max] General Discussion => Topic started by: iacdxb on 2018-11-08, 12:10:09
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Hi,
Anyone update me whats Unclipped HDRI....? I tried googled but not found any info.
And is there clipped HDRI also...?
Thanks.
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It's made up term :- ) "Un-clipped"- without clipped/clamped dynamic range.
Sun can be up to 16 stops brighter than Sky and this is not easy to capture without strong ND filter on top of extremely low exposure.
Therefore big majority of HDRi on market lack those top highlights and don't provide such strong directional light (and resulting shadows) as the light did in reality.
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Thanks for the info.
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I downloaded an hdri website on hdrihaven and it says it's 22EV but I turned on the sun with PS and it was 16EV. I wonder why or do I understand something wrong
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22 EV probably means it was photographed with a dynamic range of 22 stops. You get this if you shoot 11 exposures at 2 stops apart, which I do myself for HDRI's captured for the VFX facility I work for.
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Thanks guys for very use full information.
Mostly hdri shows over exposed, hdri should be with color correct or tonemap control...?
With this would you like to suggest a good calibration.
Thanks.
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A HDRI should technically be 'neutral'. Physical light in the real world is not 'tone mapped', that only happens once the light hits the camera's CCD, and then the camera performs an operation on the captured data.
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A HDRI should technically be 'neutral'.
This !
HDRi should look flat, almost "ugly", and if it's saved at higher exposure, with overbright highlights.
At which exposure is HDRi saved to .exr/.hdr doesn't matter (it's linear after all), there is benefit for both approaches: averaged and physical. The former will give you sort of auto-exposure look where you can directly use it for look-dev, for example in Marmoset or Unreal. The physical will have exposure where the light source will have the same intensity as in reality. Such calibration requires either lightmeter (or shooting grey ball and calibrating in 3D by eye). The lighting is the same, but the latter requires you to setup exposure in your DCC app and you can keep A-to-Z photographic approach because HDRi will match your physical camera setup.
Btw, my biggest petpevie is people who are arbitrarily white-balancing and color-correcting HDRi so they look nicer (profiling camera if you don't like manufacturer's white point and color matrix is ok though). This should be avoided (and I've seen the guy do it on his HDRiHaven blog where he desaturated yellow in one example,etc..) because this affects the light, all post-production should be done on resulting image.