"auto detect log" tone mapping yields slightly different results across two of the same camera.

[lloyd_pdx]

I have a two camera set-up, both on one sitting subject. Light is the same source. Cameras are set up the same for V-log capture. Same exposure, albeit with two slightly different lenses. Project setting is to auto detect log and apply tonemapping correction. One camera shows a more yellow skin tone, the other, more red. Is this a function of lens coatings or something else? Is there a way to further correct all clips from one camera in the Lumetri panel, or do I need to copy/paste settings via Lumetri effects controls? 

I like the tonemapping results in general, and it's definitely a learning curve and not the RGB kind 😉

Thanks.

[R Neil Haugen]

Quite likely that's as much the two cameras having slightly different color settings or responses, coupled with different lenses.

As has been noted, no capture system, neither film nor digital based, "sees" color. They only see brightness.

The color is manufactured for us by filters over the sensors coupled with a ton of complex mathematical computations. And all of that will be a bit different in every camera or monitor, no matter if they came off the line next to each other.

[lloyd_pdx]

Thanks, this confirms what I suspected and I prefer this over solving some buried user error. Although I discovered a 1/3 stop ISO setting difference, and I'm sure that will make a difference in sensor response too. I appreciate the reminder about brightness vs color, for whatever media is recording.

Related to this, can you, or anyone else reading, recommend a resource for learning how to use the tools to correct and match color in a scenario like this? I have a notable amount of color management experience in the photography realm but video and multiple cameras are the next frontier for me.

[R Neil Haugen · Accepted solution]

Depending on how far you want to go, well ... I can go a long way into this.

If you have a good chip chart, like the DSC Labs Pocket One Shot ...

https://www.bhphotovideo.com/c/product/1311293-REG/dsc_labs_posp_pocket_oneshot_plus_test.html

Or several others ... you can do some controlled shots with both cameras on the same tripod.

Of the images, first match the white points. Then the tonal values ... the gray patches, using say Waveform YC (no chroma).

Then using the Vectorscope and the hue - hue curves, make a point of a color box, then adjust the curve so that point is centered between the center of the scope and the color box for it on the outside. About midway between them. Go around the chart doing that for each. After you've done the circle, remove the "extra" points, so you only have the six color chip points on the curve.

Now reset the white balance setting.

Save each Lumetri effect named for the camera, and then from now on, drop that onto the camera's clips in the bin as a "source effect". This will give a pretty matched image between the two cameras.

I've found that most of the time, if the cameras are all set to the white balance of the scene as shooting, then in post they start pretty close relatively.

As then, about all that is left is of course do a white balance, and any trim work to get them looking like you want.

[JonesVid]

@R Neil Haugen 

This is interesting topic Neil

Regarding the technique above for helping bring cameras closer in colour /color calibration, can you point us to any good Video Tutorial which might cover this process?.

Any other info welcomed.

[lloyd_pdx]

Wow, this is generous and very useful detail for me. Thank you.

[R Neil Haugen]

JonesVid ... there are several, but I don't like any of them. They all take each color point way too far out to the box for it, and that ... for me at least, and whether in Premiere or Resolve ... just isn't "correct".

So it's just either selecting a chip with the selector icon, or at times making a smallish mask, dragging that over the chip on the chart. Then using the selector in the hue/hue curves tool. I tend to do the latter any more.

Make the couple changes, but you notice for each selector clip, you get three points, one centered, and a limiter on either side. When done, remove all the limiter marks. Or it's not a smooth result.

[lloyd_pdx]

I assume this procedure is done with Log capture? 

[R Neil Haugen]

No. It has to be done in linear display space. So if your media is log, it must get normalized first.

Which the auto tonemapping does a rather good job of doing for you. 

[MyerPj]

Thanks Neil, cool stuff! 🙂

[MyerPj]

Hmmm... @R Neil Haugen 

<<there are several, but I don't like any of them>>

Time to get out the old screen recording software... 🙂

[R Neil Haugen]

I'm planning on it. Another month or so.😉

[MyerPj]

Let us know here 🙂

[R Neil Haugen]

Will do.