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RED ISO rating


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#1 Philipp Kunzli

Philipp Kunzli
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Posted 12 June 2010 - 06:20 AM

Hey everybody

I't might be a silly question but I'm slightly irritated.
As one knows, or also prefers, is the native sensitivity of the RED between 250 - 320 ISO

As David Mullen wrote is one able to work in RecSpace mode up to 1000 ISO with fairly noise.

My question now is, what about the post production with Raw files.
For example: I'm "rating or setting" the RED on 1000 ISO and expose everything for this sensitive.
Doesn't have the native Raw files still a sensitivity of 250 ISO (to make it easy) and in that case aren't the RAW files actually 2 stops under?

My two last shoots on the RED were all Outdoor or we light everything for "250".
Since that in post, during the final grading on a Film Master we were able to work with the RAW files and their full range of information.
Of corse, the Raw Image looks like a Ultra Low contrast print, but thru the big amount of information it doesn't really matter...

Does it mean, what I highly assume not, if one rates the RED on 1000 ISO that you're only able to work on REC space during post? And you don't have the full range of the Raw-Information. Or is it, that the whole post is Raw File based and the "RED Space" is a "software or proxi" way which converts or calculates realtime the Raw Files into
the Rec Space "look".

If somebody is able to give me an breve explanation, how they worked/rated on the set as well as the whole post...
I'd highly appreciate that.

Thank you guys.

Philipp
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#2 David Mullen ASC

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Posted 12 June 2010 - 10:11 AM

Whether you are working at 100 ASA to 2000 ASA, you are always working with the full dynamic range of the sensor -- the only difference is whether that range includes more shadow detail versus more highlight detail. With the slow ASA ratings, clipping becomes a problem, and with high ASA ratings, noise becomes a problem. But if the system is low enough in noise overall, then you have more flexibility in using the higher ratings and thus gain more highlight information without worrying as much about noise.

You don't really "look" at RAW images, they are not really viewable - they are always converted into RGB to be viewable. In post, you convert the images using the metadata for white balance and ASA rating, into RGB - in whatever gamma and color space you want: Rec 709, RedLog, RedGamma, etc. There is no right or wrong choice, it just depends on what works better for your colorist and intended output. Some systems allow you do to the conversion in real time directly from the R3D files, which gives you more flexibility in adjusting the conversion parameters if you feel you can get more info out of one method or another. But most post places convert R3D files up front to 10-bit DPX files, usually in some Log format.

If you shot at 1000 ASA, you don't have to convert at 250 ASA and then brighten the images up in post. Occasionally if you have a clippy shot, there may be some advantage of converting the shot at a lower ASA value to squeeze another bit of info out of the highlights, but it won't be much, maybe 1/3-stop extra detail if you are lucky. Otherwise, the conversion process is generally set-up to use all of the dynamic range recorded as a starting point for creating the gamma output format, and there are controls in RedCine-X and whatnot to adjust that.
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