[Tig] Working with LOG

Craig Leffel craig at optimus.com
Wed Feb 9 02:22:04 GMT 2011


Hi Rory -

The first question I would ask is what Color Corrector are you 
attempting this on? All systems will have a slightly different approach, 
but any that have native R3D support should work, the display setup is 
what will be different.

As far as your statement about Film being the only thing that works in 
Log... not really true.

Think of Log as purely a Colorspace and a particular way to map values 
of RGB, and black and white points. Lin is just another color space with 
a different mapping of RGB and black and white points. You can go back 
and forth between these 2 and in the same way you can use LUTs ( Look up 
tables are RGB mappings ) to re-map RGB values to a display, a 
filmstock, or a camera input.

The purists lurking here will point out the errors in my definitions, 
but as a colorist trying to work, you will have success if you think 
about it this way, and not try and get too deep into the Log/Lin game... 
because then the bit depth conversations start, and it's a very long 
conversation.

On a Baselight for instance, you can do a manual Log/Lin correction or 
you can use a LUT. In R3D files, if you select Rec709 instead of RedLog, 
you've already done it... but who wants to color correct that way? I 
certainly don't..... and won't.

You can also think about it this way - Log space is a film curve that 
just seeks to hold detail - a nice S curve to the data - no matter where 
it comes from, digital camera, film, or 16Bit Raw file. Lin is just a 
straight line between the darkest area and the lightest, and clipping 
will occur. The scale ( how many slices/ bits ) doesn't really matter at 
that point- clipped is clipped.

In a number of color correction environments you can have Log material, 
work in Log, and let the display card do the Lin conversion, so you're 
actually seeing what Lin will look like. When done, you render Lin files 
and if all things are setup properly, your Lin files will match what you 
were color correcting when they're played out on another linear display.

That's just a layman's explanation, but maybe it helps.

Craig Leffel
Senior Colorist
Optimus




On 2/8/11 7:11 PM, Rory Hinds wrote:
> I'm still trying to get my head around working with LOG files and am hoping you can clear up some of my logic or lack there of.
>
> My biggest head bender is that when you work with LOG you have to do a LOGtoLIN conversion to view the file on a LCD or Projector as the only medium that works in LOG is film.
>




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