RGB Mixer problem

[Tom Evans]

I have checked preserve luminance and monochrome but when I move the slider in the RGB mixer, it doesn't have any affect on the images. This is confimed by the scopes. It's probably a small thing that I've been missing?

[Abby Bader]

Make sure to NOT desaturate the images before clicking monochrome. Typical mistake. The sliders need color values to work. 

[Tom Evans]

Thank you! I didn't realize that checking the monochrome button gives you access to the color information behind the non-color representation of the image.

[Abby Bader]

It's a great tool. The different color channels can be used to add and subtract nuances and shape an image to be something really different. Just be careful that it could introduce some unwanted noise. I often find that I have to add some subtle grain before rendering to help match the noise levels.

Edited November 9, 2016 by Abby Bader

[Nicolas Hanson]

Playing with the sliders could create an incredible depth to b/w images and the noise add texture that could be a great thing to make the image look bolder. 

[Frank Wylie]

Tom,

Also, if you are not using a control surface, be aware of this potential problem:

https://mixinglight.com/portfolio/work-around-mouse-math-bug-davinci-resolve/

It was addressed in 12.5.3 release, but I always add a new serial node anyway when working with independent RGB curves in a grade to avoid any weirdness...

Frank

[Abby Bader]

I would also add that you could play around with the luma curves both before and after the monochrome node to get more interesting behavours.

Using the luminance curves to clip the highlights will introduce silver, as mentioned in Damiens article, and that could also be powerful to the B/W look. 

[Pepijn Klijs]

On 2-12-2016 at 9:53 AM, Abby Bader said:

I would also add that you could play around with the luma curves both before and after the monochrome node to get more interesting behavours.

Using the luminance curves to clip the highlights will introduce silver, as mentioned in Damiens article, and that could also be powerful to the B/W look. 

Hi Abby,

What do you mean with luminance curves with regard to Resolve? You mean the 'custom curves'? And who's Damien and where can I find the article you mention?

 

Thanks!

Edited December 7, 2016 by Pepijn Klijs

[Abby Bader]

Hi Pepijn. Sorry, should have linked to the article 

[Pepijn Klijs]

Ah great thanks! I actually read that article when it came out... should have remembered.

[Thomas Singh]

Changing the different values in the monochrome mixer can play an important part in storytelling. In this shot the director wanted to make the blood on his hands stand out, and in others we worked with texture and definition and handled banding artifacts.

Edited December 12, 2016 by Thomas Singh

[Marc Wielage]

Yes, the RGB mixer can do some very interesting things. I have had situations where the camera clipped one color channel but the others were OK, so I was able to "steal" some detail from the two other channels and get the channel a little more detail. This is a huge help for faces when those are clipped red. 

I have worked on a few features where camera clipping made us nuts, and this was in the days prior to Resolve (very early 2000s). I would love the chance to redo some of those shots, because I think now we could salvage them in a way that wasn't possible 10-12 years ago. 

It's also dynamite for B&W correction for projects shot in color, because it allows you vary the grayscale response so dramatically. It's a huge, huge help in cases like that. 

[Tom Evans]

Marc, would you prefer the client to shot for B/W in color because of the monochrome mixer benefits?

[Marc Wielage]

On 1/4/2017 at 1:53 AM, Tom Evans said:

Marc, would you prefer the client to shot for B/W in color because of the monochrome mixer benefits?

If they're shooting on a digital camera, yes, I would rather they shoot in color so I could manipulate the RGB channels in monochrome mode. I did several B&W music videos from film in the 1980s, and in one major case, they wish they had shot in color because they wanted to do a color "effect" at one point. But back then, we didn't have the power of the RGB mixer. 

[Adéyẹmi]

On 11/10/2016 at 12:17 AM, Abby Bader said:

It's a great tool. The different color channels can be used to add and subtract nuances and shape an image to be something really different. Just be careful that it could introduce some unwanted noise. I often find that I have to add some subtle grain before rendering to help match the noise levels.

by any chance do you know how this monochrome mode on the RGB mixer is achieved using either colour crosstalk or colour matrix on BL?

[Marc Wielage]

On Baselight, no. It's a powerful system, and I'm sure there's an equivalent of it there.

[Adéyẹmi]

5 hours ago, Marc Wielage said:

On Baselight, no. It's a powerful system, and I'm sure there's an equivalent of it there.

Thanks.

[Anton Meleshkevich]

Sometimes I use RGB mixer with node gamma set to linear. Especially for teal orange thing, when I add green channel to red channel and subtract blue channel from red channel. When set to linear, separation to complimentary colors is a little bit different. It can help if you don't want to shift greenery to yellow when you make teal orange things by RGB mixer. It will shift. But not so much.

Of course timeline color space should be set to footage color space. And your footage should be log. Otherwise it will be difficult to notice the differences.

 

Here is a colorchecker shot on URSA Mini 4.6K in CinemaDNG, then cropped and zoomed. A Log to Rec709 LUT is applied after RGB mixer in the next node.

First image -  RGB mixer applied to log gamma footage.

First image -  RGB mixer applied to linear gamma footage.

I adjusted RGB mixer slightly different in terms of effect strength, because it acts different when applied in different gamma. So it's easier to compare the difference now.

Edited October 22, 2018 by Anton Meleshkevich