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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Shooting Redlogfilm vs gamma 3

Nathan Apffel said:
I am used to LogC on the Alexa, but RedLog functions much definitely for me due to the different color and gamma spaces I can choose. We had viewed on set in RedLog and the histogram appeared to be exposed properly.
Click to expand...

If you look at the images below, you can see that what you would see on a waveform with a camera pointed at a hypothetical perfect linear light gradient from 0% to 100% would be very different when viewed through the three different "gammas". If for example you are used to how ALEXA LogC looks on a waveform, and you adjust your iris so a REDlogFilm image looks comparable, you will be about a stop underexposed.

gammas.png
 
Log C is strangely named as it doesn't meet the cineon spec which is what we'd all assume from the "C" in the name. It also varies on ISO so there's a different log c equation for each and every possible ISO setting making inverting it in post a nightmare.

With REDLogFilm it follows the cineon spec precisely and is valid over a wide ISO range - (any ISO up to ISO3200 at which point there's some mild compression to fit all the code values in) and is easily and instantly invertible to linear light for VFX work via the standard cineon equation in Shake, Nuke etc. (default log2lin settings work great or just interpret the dpx as cineon) and hence matches the RED exr linear light output.

Graeme
 
Les Dittert said:
Can someone from RED clear this up please :

Blackshading does nothing to effect random temporal sensor noise ( call it grain ) , right ?
I keep seeing people talk about blackshades for noise . Other than possibly sinking the blacks to darken and make noise less visible, it is still the same noise remaining after a black shade.
Black shade is for correcting field unevenness and for fixing hot pixels. Yes ?

Graeme ?
Click to expand...

as i'm aware it does not effect random temporal sensor noise, just the fixed-pattern kind - as well as some other stuff that's not entirely clear.
 
"Black shade is for correcting field unevenness and for fixing hot pixels. Yes ?" - yes.

Graeme
 
Graeme Nattress said:
Log C is strangely named as it doesn't meet the cineon spec which is what we'd all assume from the "C" in the name.
Click to expand...

Although Blackmagic Design incorrectly say in the Resolve user guide that LogC is "identical to the Cineon Log gamma curve".
 
Anyone interested can see the Log C equation (x > cut) ? c * log10(a * x + b) + d: e * x + f differs from the standard cineon equation.

Graeme
 
For reference cineon equation is:

(300 * log10( (1-0.0108) * x + 0.0108) + 685) / 1023

Graeme
 
Graeme, why is it that when I have redlogfilm enabled in camera I have reduced frame rate availability? I too thought that I was pulling more information by using redlogfilm, especially since when it is enabled my EPIC at 5k frame rate only goes to 96fps, instead of 120fps.
 
seems like a bug to me.

Jon Jones said:
Graeme, why is it that when I have redlogfilm enabled in camera I have reduced frame rate availability? I too thought that I was pulling more information by using redlogfilm, especially since when it is enabled my EPIC at 5k frame rate only goes to 96fps, instead of 120fps.
Click to expand...
 
Sounds like a bug - I can try to duplicate here although I only have Epic, not Scarlet.

Graeme
 
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