Is there an automatic way to perform color correction?

[Name]

Hi all,

Is there an automatic way that analyzes a video clip and kind of creates an automatic color correction preset? Something like a LUT.

I have some clips with some wrong colors, for example:


[Attachment 85324 - Click to enlarge]

Just for fun, I loaded the image within Adobe Lightroom and tried to use the "Auto" mode to see what would happen, but the result was not really better.

I also tried to set some white points manually, but this didn't also go well.

These were just some quick and dirty tries to see if for video snapshots it would work as easy as for pictures.

Now I'm wondering if there is some automatism to kind of get the colors right and the fine-tuning, if needed, I do manually.

Any script/tool or that's a manual trial & error process all the way?

Thanks.

[davexnet]

ColorYUV with AutoWhte in an Avisynth script may be a starting place:

[Alwyn]

Autowhite=good stuff!

[Sharc]

It may be more pleasant to view it grayscale

[Attachment 85334 - Click to enlarge]

Manually you can try to align (center) the U,V channels to taste, observing the histogram:

converttoYV16(interlaced=true)
coloryuv(off_u=6.0,off_v=3.0)
histogram("levels")

[Attachment 85335 - Click to enlarge]

[lollo]

To start:

https://www.cambridgeincolour.com/tutorials/histograms1.htm
https://www.cambridgeincolour.com/tutorials/histograms2.htm

[Hunk91]

Virtualdub + Auto-levels (by Livio Cicala)

[Attachment 85339 - Click to enlarge]

[Alwyn]

Colormill in VDub. You can save these processing settings and load them quickly on later clips (together with anything else you've set up, eg cropping, resizing, export parameters).


[Attachment 85340 - Click to enlarge]

[jagabo]

ImageSource("capture.png", start=0, end=23, fps=23.976) 
RGBAdjust(rb=-30, bb=-60)
RGBAdjust(r=193.0/203.0, b=193.0/183.0)

Blown out windows turn green though.


[Attachment 85345 - Click to enlarge]

Most auto whitebalance filters will be confused by the bright white windows at the top of the frame. Removing them helps a lot:

ImageSource("capture.png", start=0, end=23, fps=23.976) 
ConvertToYV24()
Crop(0,80,-0,-0)
ColorYUV(autowhite=true)

[Attachment 85346 - Click to enlarge]

[Darryl In Canada]

DaVinci Resolve (free version) has the best color correction tools, and has an automatic color feature. But it may not be able to correctly guess the correct colors if there is some kind of weirdness going on with that tape. To try to get the most from the automatic feature, try Trick #1 in this video from Learn Color Grading. It yeilds slightly better results than the regular auto-color feature in Resolve.

[poisondeathray]

[Attachment 85351 - Click to enlarge]

Gammac is another option for the starting point, but it works in RGB
http://avisynth.nl/index.php/GamMac

gammac(lockchan=0, show=false)

[Name]

Thanks for all the input.
One general question, should the color correction be done before or after the deinterlacing?

[poisondeathray]

One general question, should the color correction be done before or after the deinterlacing?

It depends.

e.g. If some issues affected 1 set of fields (e.g. even fields) more than the other , not just color manipulation, maybe noise or other problems, you might address field specific issues first before deinterlacing, otherwise you risk "contaminating" the other fields

It's hard to tell with just 1 frame, but there is a slight U shift on the even field. Is that going to be a pattern, is it chroma noise affecting 1 field ?

[Alwyn]

DaVinci Resolve (free version) has the best color correction tools, and has an automatic color feature. But it may not be able to correctly guess the correct colors if there is some kind of weirdness going on with that tape. To try to get the most from the automatic feature, try Trick #1 in this video from Learn Color Grading. It yeilds slightly better results than the regular auto-color feature in Resolve.

Can you show us what Resolve does with this image?

[Name]

How is the AutoWhite filter applied:

ColorYUV(autowhite=true)

Is it based on each frame? Will the first frame be used for the whole video? Or will an average of the video be taken?

[jagabo]

How is the AutoWhite filter applied:

ColorYUV(autowhite=true)

Yes.

Is it based on each frame? Will the first frame be used for the whole video? Or will an average of the video be taken?

Each frame. This can lead to changing colors during a scene.

[Name]

Each frame.

If it is done each frame, should the white balance not be done after the deinterlacing?

Could it not be that as the even and odd lines of an image are represented on different frames, in the worst case, the line pairs are increasingly defined/worked out. As they could have a different white balance applied when merged together? (I hope it is more or less clear what I want to say. )

[jagabo]

I don't really know enough about how AviSynth's white balance works to know if it makes a difference whether you deinterlace first or white balance first. You ought to experiment and report what you find!