how to fix a color issue on bright areas

[mathmax]

Hello

I would like to fix the problem on the bright area in the image below. I just want to make it white.. but I really don't know how to do.



When, I play with the Levels(), I notice that these pink areas remain stable.. I can darken or whiten the image completely, these areas (and only them) will always remain pink.

Also, is there a way to fix these annoying 'waves' on the film..



Here is a sample to download : http://www.mediafire.com/?47bz11g1hf28y30

Thank you in advance for any advices

[jagabo]

Something like this maybe:

mask=ColorYUV(off_y=-200).ColorYUV(gain_y=20000)
Overlay(last, ColorYUV(last,cont_u=-256, cont_v=-256), 0, 0, mask)

You can fine tune it.

Or maybe a mask built from the U channel (U is very high where the purple colors are), or both Y and U. Or try a chroma key.

Chroma based mask:

 mask=UtoY().BilinearResize(width,height).ColorYUV(off_y=-120).ColorYUV(gain_y=10000)

[mathmax]

Thank you

The weird thing is that this purple area SHOULD be the brightest part.. but because of oversaturation, it becomes finally less bright than the rest. Is it due to a wrong YUV<->RGB convertion?

As a result, your script will paint in grey the purple areas which is not so nice..

[jagabo]

Thank you

The weird thing is that this purple area SHOULD be the brightest part.. but because of oversaturation, it becomes finally less bright than the rest. Is it due to a wrong YUV<->RGB convertion?

Something like that.

As a result, your script will paint in grey the purple areas which is not so nice..

You could try brightening the grey image before Overlay(). Try adding gain_y=20 to the ColorYUV() statement.

[mathmax]

Thank you..
I tried to reduce the saturation for the light areas in Color Mill and the result is not so bad.. at least no limits are visible like with the use of a mask.
But well.. I was hoping we could do better regarding this problem

[mathmax]

Do you have any suggestion about the 'wave' effect?



[Attachment 14520 - Click to enlarge]

[jagabo]

I'd probably leave the purple splotches. It' part of the charm of the video. Neat Video might help with the wavy bars.

[jmac698]

Causes

-Caused by the lens originally
I get purple halos even in my modern digital camera. One explanation is chromatic abberation, where some colors of light are bent differently than others leaving haloes, especially at the edges of the lens. That doesn't seem the case here.

-Caused by the camera originally
The other reason is sensor saturation; maybe the green channels are clipped while the other channels are close to clipping, leaving a purplish colour.

It could be that due to the white balance of the camera, the raw green values were relatively boosted.

It can also come from non-linearity of the ADC near saturation which does happen, but that only applies to modern cameras.

If this is old footage, then a whole other set of camera artefacts apply from tube cameras. I'm not as familiar with these.

-Caused by VHS
Finally it could be an effect of VHS, but I don't know the reason.

Solutions

To fix it, I'd try some techniques from re-colouring, like the colorit filters. They can be used to do a type of flood fill or to selectively replace all purple colours with white.

As for the wavy lines, you need vcmohamn's fan filter plugin, it's made just for this. (fan refers to the interference caused by a fan motor on a VHS on the same electrical branch circuit)

References

http://avisynth.org/vcmohan/ColorIt/ColorIt.html

http://avisynth.org/vcmohan/FanFilter/FanFilter.html

[sanlyn]

The pink flare is from a pink spotlight. You can see it's aimed at Michael and is directed onto the stage floor (pink circle in lower right). It's not supposed to be white.


[Attachment 14786 - Click to enlarge]

[themaster1]

my gut feeling tells me it's a chroma key issue (seeing that there is a label in the middle of the frame...)

old school chroma keyer... so 80's