Set black and white balance node/s?

Hey all, hope you are all well.
I was just wondering what is the fastest way to set the black and white balance in a node setup?

Ideally I would like to pick a black colour from the plate and have my model’s black level set to that, all in the node setup, and the same with the whites.

I can kind of do it by adjusting brightness and contrast then adjusting the hue of the lows and highs in colour balance, but its a lot of messing around :confused:

Is there an easier way?
Cheers.

You can skip the Brightness/Contrast node and do it all in the Color Balance node. The three vertical grayscale sliders act like Levels controls.

Steve S

Thanks for the reply Steve,
Yeah I have tried using that, but the eye dropper doesn’t exactly set the balance, I need to be able to pick something visually black off the plate then set that as the black for my render, and the same with the whites too… I think matching black and white is one of the first things when compositing CG with live action.

Obiwan says “Use the scopes Luke”. White and black points should be in the middle of a vectorscope and a 3-way waveform display should have top (white) and bottom (black) points landing at the same place for each colour (RGB).

Is this any help?
[video]http://youtu.be/mq4iLQxsW7w[/video]

Thanks 3point, the video helped too, I guess I will have to play around more with the colour balancer then. I thought there might be a quick, pick and set for black and white somewhere in one of the nodes.
Will keep trying,
Cheers.

You sort of can if you place a divide node on top of your footage, then select a color cast from the source to reverse out. But this tends to increase the value of the image potentially clipping whites/highlights.

Thanks mate! I’ll give it a go,
Cheers.

I also played with the colour correct node and it is way better and preserves luma values.

The RGB Curve Node?

To be honest even the dunbest of editing apps. have a one click white balance (and for extra points a black balance too). In Photoshop I would just sample the offending colour and invert add a layer on it.

The RGB Curve Node does. :wink:

oh, doh!

You could take the before and after images and blend them together with a Mix node. Adjust the Fac number to until you like the result. I often do this with still images in Photoshop Elements because the color correction tool often goes a bit overboard. I duplicate the image onto a new layer, apply correction to the top layer and adjust its opacity.

Steve

You definitely need to use the “scopes.” Final color adjustments really do have to be objectively measured. Blender gives you all the knobs and controls you need to adjust the problem, but you really can’t trust your eyes on this one. You need to be looking at a scope.

I did notice the RGB curves have Black Level and White Level, but, how come when I pick a black as a grey as a test, it makes the output ultra dark instead of matching the Black colour?

Yeah, I think you and 3pointedit are right, it seems most accurate to do it through the Scopes! I’ll have to learn more about Scopes.

In my humble opinion, “one-click controls” might be a good rough-start, “to get you into the right neighborhood” so to speak, but the process is far trickier than that in actual practice. You’re going to be eyedropper-sampling a lot of pixel values, looking at a lot of histograms and other “scopes,” and using quantifiable, numerical methods to obtain the results you need. Just like musical recording: you can take “it sounds good to me” up to a point, but then you have to start using the meters.

If you’re doing a complicated rendering, you might need to shoot a single still-frame and do balancing on it … perhaps adjusting some of the up-stream components, and if so, “now’s the time to be doing it.” (You need to look at individual shots from each of the scenes in the entire show, so that you can get a rough sense of color-continuity, before you commit to rendering them all!)

Agreed. Usually, balance first (get everything even) then grade second (apply the look). It is helpful to get a 1 click head start in a proper color tool that shows you where the color is heading, then push on from there.

Playing with the Curve tool’s white and black points aren’t quite as flexible. White in a video image is often peak value (r=1.0, b=1.0, g=1.0) while the cast begins further down the range but if you make that lesser value white then you skew the contrast of the image. So re-targeting the white (which is usually already white) isn’t as valuable as re-targeting mids.

Where are you sampling values and is this with Color Management On sounds like its sampling linear values and applying them which would obviously be a bug.

re Scopes, useful for analysis to back up eyeballing it but good idea to close scopes in the viewer before rendering seems like the scopes are sampling whilst blender renders slowing rendering down significantly.

Although no where near the control I use the colour balance tool in the VSE rather than nodes and very limiting tools in the VSE but speed of feedback is so much quicker although if do you VSE make sure make float is activated and be aware VSE does not blend in linear light AFAIK

Many thanks everyone for your suggestions,
Here is the WIP! Just uploaded to Youtube,
I realize the track is a bit off, and I want to blur the shadows a bit.
Needs to be watched in HD I guess as lower res loses a lot of binding effects.
Anyways, enjoy. :stuck_out_tongue: