[ocs-dev] Re: The S-Log formula
Alan Jones <sky...@...>
On Thu, Aug 12, 2010 at 12:01 PM, Jeremy Selan <jeremy...@gmail.com> wrote:
Ah, when you read Sony Camera documents you often have to put on yourIndeed - I'm still pretty fresh to dealing with this stuff so directly. Time to
re-read Poynton's Digital Video.
Which camera are you using? We've done a few Sony cameraYes - the F35 :)
In my experience, if you have theAnywhere you could point me to for reading up on doing this and using it
to generate LUTs?
Sometimes it's a communication issue, but more often theYeah - I've taken the formula as being input space and then applying
linear to rec709 to the result in order to generate the slog to rec709
Are you referring to this document for the formulas? (SRW_ITG_S-Yes.
Assuming we trust the document for the moment, I think the rule ofAhhhh - thanks :)
So when the document says "t has a range of 0 to 1.09", I take this toPerfect :)
In the later example "S-Log Formula" this is already taken intoI'm still trying to figure out where some of these values come from. The
1752 is Reference white minus Black level and the 128 is black level.
Though the 379.044 and 630 are still mysteries to me. I've tried dividing
them by the equivalent part of the formula (though I've been using anti
s-log to work on this rather than s-log, but same numbers anyway) and
the resulting numbers don't have any easily identifiable correlation with
either the input or output spaces.
I'd love to know how those are calculated as at the moment I can get my
results close when trying to find a generic way to deal with the formula
(so I can make it for an arbitrary bit depth), but not exact.