REDgamma2 vs. REDLogFilm

[Toby Tomkins]

Redlogfilm emulates the gamma curve of cineon film scans (although this is a bit of a misnomer as all film stocks have a different curve). If you grade in log you should use a LUT at the end of your grading chain (or display LUT) to perform a log to linear conversion so it can be represented (viewed) in a standard colourspace for a given target so say rec709/P3. .

This lets you have a full range wide gamut log graded master that can have LUT’s applied to create high quality conversions to deliverables in any colourspace (rec709, p3, print etc).

As far as I understand, this workflow has aeasthetic arguments (you might be able to achieve softer shadows and highlights), but a technical standpoint is only NEEDED if your target colourspace (say P3 or film print) has a gamut that extends beyond your viewing colourspace.

I’d love to hear from others on this though! (-:

[Mike Most]

>Redlogfilm emulates the gamma curve of cineon film scans (although this is a bit of a misnomer as all
> film stocks have a different curve).

It’s not a misnomer at all. Cineon is a defined format that is used to store the information gathered by a film scan. It has nothing to do with specific film stocks. It is simply a way to capture most if not all of the information film chemistry can capture. Think of it more like a codec – if you compress using ProRes, for instance, it really doesn’t matter what camera is doing the shooting. You’re simply taking the resulting video image, compressing it, and putting it into a standard format that other software can then interpret. Same thing with Cineon. The fact that you can see the image is probably a drawback because that’s not an image that is intended to be viewed directly. For more information, you might want to look at 2 posts I did in my blog on this very subject (mikemost.com).

[Toby Tomkins]

I completely agree, but it should be called RedLogCineon, not RedLogFilm, thats the misnomer.

[Andrew Smith]

Thanks for the replies guys.

So is it ok that I did not apply any LUT at the end of my node chain when doing a grade for web? Should I have if it were for broadcast and/or film? Which LUT would you recommend I use and wouldn’t that then change my entire grade’s look?

I am still a little confused as to whether or not I should use REDLogFilm or not, and if so when?! Following warren eagles tutorials / videos and others I was initially under the impression to have RED stuff start at 2 across the board – that the color science was ‘better’ but as I mentioned, I have recently also seen people use the REDLogfilm option and I just want to better understand things.

Thank you for any more info that can be provided on this subject, much appreciated!
Andrew

[Kevin Cannon]

Another consideration is that the way the director and DP have worked with the camera can lead you in the right direction. If you have a DP that has a color-critical Rec 709 or p3 monitor on set, in a tent or reasonable lighting conditions, they might be basing many of their lighting decisions – contrast ratios, highlights, fill for shadow details – on the exact RED settings or LUT that they had set in camera and monitored on set. In such a case, creating your own transform to replace the ones they selected might only take you further away from what they’ve already achieved, or take you longer to arrive at the same result.

Of course, you can also be working with a team that shoots using a light meter more than a monitor, perhaps envisioning a characteristic curve for the image that isn’t a typical camera setting. Those might require you to eschew the default settings and create your own curves to bring RedLogFilm or Log-C into line with the vision.

KC

Prehistoric Digital
PhD Grading Suite

[Toby Tomkins]

You could use a redlogfilm to redgamma2 LUT to have the flexibility of a log pipeline with the same initial starting point as redgamma. Working in log is different though, the way lift, gamma and gain respond is different to grading linear data, and I’m not sure I like it because you normally have to compensate the other two while working on one, ie, if you change the gamma (mids) the whole image changes (because with log images all the data is in the mids), so you have to compensate with lift and gain.

[Mike Most]

Which is exactly why a number of us have been “prodding” Blackmagic to add a log grading toolset to Resolve.

However, until that happens, you can use the offset controls in place of an exposure control, and the lift and gain masters as a contrast control to essentially achieve similar results and a much better feel when working with log material. As you mentioned, lift gain and gamma are controls that are tailored to and scaled for use with video gamma material, not log original. Since there are currently no pivot controls and no range limiting controls for them, it’s not an optimal way to deal with log material.