How much of RCX is raw processing?

[D Fuller]

I was doing some experimenting with channel mixing to B&W in RCX tonight, and I came across an interesting phenomenon: If I reduced the saturation to zero, I could use the RGB controls like the Channel Mixer in Photoshop and get the results I expected. But when I started playing with R,G,& B curves, the B&W image is being colored. (like a duotone, not full color) I expected this in the lift, gamma, gain module, but not in curves.

This got me thinking about the signal path in After Effects, where the raw conversion is done in the import module, and everything after that is working with the RGB result of that import step. It looks like RCX is doing the same thing -- except that you have the raw tools and the post-raw tools open at the same time. Does anyone know the answer to this? And if it's true that curves are a post-raw tool, does anyone know how curves work in the camera as part of a look?

 

[Michael Hastings]

Wouldn't the RGB curves HAVE to be post raw since the raw really is just a black and white image shot through a pattern (bayer pattern) of colored filters - so color doesn't exist until you use the debayer algorithm?

 

[paulherrin]

shot in the dark.

okay... color curves are basically just individual curves for each channel, then they are mixed together. i believe that could lead to values that don't equal exactly 1 for each channel (don't lose any sleep over it)... which would mean some adding and subtracting of color, hence they begin to do the same things essentially as the lift, gamma, gain to the image.

not sure if this is a problem that needs to be "fixed", but the saturation could be applied to the image after the curves, just order of operations.

so for your real question, there's enough data to accurately generate the curves without hurting the image or the data - it's all still there. i'm not sure i'd worry too much about this post-raw business until you've either converted it to another format, or are working in another application and start applying operations to the image.

so in camera, i would just think about it (kind of) as a LUT. it's non-destructive, and you obviously can still change it at any time.

now, there could be deliberation about pre, mid, or post-debayering... but it might just get esoteric - doesn't matter that much with the data we get.

i'm sure graeme or some of the RC-X team, or someone that knows more about this kind of thing could clear it up much more effectively.


long story short. just use the luma curve. OR, desaturate it afterwards, and preview it in RCX in another monitor that's desaturated.

 

[D Fuller]

Wouldn't the RGB curves HAVE to be post raw since the raw really is just a black and white image shot through a pattern (bayer pattern) of colored filters - so color doesn't exist until you use the debayer algorithm?

That makes sense, but the RGB sliders just above the curves tool in RCX seem to work on the mix of raw data. If you drop saturation to zero, they still change the B&W mix, much like the channel mixer in Photoshop. The green channel also has about twice the luminance value of the red and blue channels (which makes sense, given the nature of the Bayer pattern.)

I'm really trying to figure out if it matters for curves in camera monitoring. Maybe not. But I'd never thought about it before quite this way.

 

[paulherrin]

like i said, i wouldn't worry about the in-camera monitoring curves. with another camera, yes i definitely would, but that's a moot point. i mean, you can always reset everything in RCX, correct? i.e. it's non-destructive. the only thing it is going to matter for would be the look for your proxies.