BMCP4K - Prores extending IRE rande 0-109%

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Krzysztof Sobieranski

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BMCP4K - Prores extending IRE rande 0-109%

PostTue Feb 04, 2020 2:03 pm


From the beginning of work with the Blackmagic Cinema Pocket 4k camera, I have a problem with the way of saving the image in the Prores codec (all ranges). The problem concerns clipping highlights above 100% IRE.

I once reported a similar problem to Blackmagic which concerned the same issue but the recording in Blackmagic VideoAssist recorders. Then after my intervention on the next update, this error was corrected and eliminated. Unfortunately, after years of new BMCP4K cameras and probably also 6K cameras, he still performs. Strange.

I will explain what's going on. Cameras of other producers currently available on the market, e.g. Sony FS5, FS7, FS7MK2, FX9, Canon C100, C200, C300, C500, Panasonic EVA, Atomos recorders, etc. do not limit image recording only to the range of 0% -100% IRE. Especially when it comes to the lightest range above 100% IRE, they allow a range of up to 109% IRE. This makes it possible in post-production color correction, recovering some information from the lights and thus obtaining a greater tonal range.

Question. Why Blackmagic again limited this possibility, since all other producers give the possibility of writing in the range of 0% -109%. ???

Yes, in BRAW mode we can recover even a larger range of highlights, but in Prores the 9% is also a lot and should be a standard.

I am asking you to restore this possibility because in my opinion it is some artificial limitation, which has no justification and limits the usefulness of the work with the PRORES codec.

This is a serious limitation and should not take place at all.

Best wishes. Chris.


Blackmagic Design

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Re: BMCP4K - Prores extending IRE rande 0-109%

PostTue Feb 11, 2020 12:22 pm

We do use "extended range" depending on the ISO set in camera. In general our log curve goes over code value 940 (10bit) for ISO's above 800. With the Pocket 4K/6K this log curve "resets" when the analog gain changes (after ISO 1000 for example).

So we don't limit to 100% and do go over when the ISO and log curve require it. All the range the sensor provides including highlights is maintained in the ProRes recordings providing you record using "BMD Film".

**Any post by me prior to Aug 2014 was before i started working for Blackmagic**

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