Extreme Color Cast on Video

[Zagorchinov]

Hi,
I want to make a very bluish and cold image for a student short movie which I'll shoot next month.

So, I was wondering what is the best way to achieve the bluish cast:
1. to use strong correction filters on camera or
2. to cheat the white balance or
3. to shoot strait and do it in post

or all of them at the same time?

The camera is Canon XL. My concern is the picture quality and since the miniDV signal has very heavy compression in the blue channel I was wondering what will happen if the picture is primary blue and where is the best point in the process for introducing some stronger correction.

I am considering to test this before the shooting, but I will be thankfull if someone shares some expirience with me.

Thanks in advance.
Dian Zagorchinov, cinematography student from Bulgaria

 

[MarkG]

The upside of doing it in post is that you can make sure you get exactly the look you want. The downside of doing it in post is that DV is 4:1:1 or 4:2:0, so extreme changes to the color balance there can create horrid artifacts around the edges of objects where the color bleeds out.

Personally I'd go for the 'do it in post' approach, but I'd want to do some tests first to make sure that it's possible without getting really ugly color bleed.

 

[Zagorchinov]

That's exactly what I am trying to figure, thanks MarkG.

But a new question apperared in my head - if the actual light in the lens is blue (when doing the correction with filters) will there be a color bleed again? I assume the compression will again throw out maybe half of the blue color resolution, so an "entirely blue" image will result a low res picture.

I'll test some heavy compressed jpeg files today, I think I should convert them to LAB space to have similar color space like 4:1:1 and then experiment with major color cast on them.

That's for now, will be glad to hear some thoughts.

 

[MarkG]

My guess is that it won't be as bad if you do the color in-camera. It's the fact that you're compressing at 4:1:1, then decompressing, changing colors and recompressing that seems to cause the worst color bleed.

 

[Zagorchinov]

Ok, tested some still camera jpg files today, just to figure out the process.

Basically, I took a hi-res jpg (virtualy loseless compression) from dpreview.com and applied a fake compression algorithm to it - convert to LAB, then strong pixelization and little blur of the two color channels. Then convert back to RGB. The result of the "compression" is normal and predictable - no distinct result in the composite picture, but heavy noise and pixelization in the three RGB channels. I am assuming that this is like what's going on in the camera's compression algorithms.

I've applied a strong blue tint before my "compression" in the first test - this is like a fake correction filter, placed before the CCD.

Then in a different copy of the image, the blue color was applied after the "compression" - this is like a post production correction.

The result is a very similar overall color cast in the two images, but:
1. The "filter" corrected image is a little bit fuzzy, there are some strange dark blue colored edges in the image.
2. The "post" corrected image has fine resolution, actually with no artifacts.

Also, the "post" corrected image has some nice color information, despite the heavy tint, as opposite to the "filter" correction where the red channel is with actually no information, which makes further color correction or backing to neutral color impossible.

So, for now definately: post correction (if there is a good software for correction).
I should consider filtration and white balance cheating, but with less strong tint and of course if I have enough light to expose with a blue filter.

Yet, this is not enough, I am planing a test with the camera next week.

Dian Zagorchinov

 

[David Mullen ASC]

My general rule when shooting digitally is sort of getting it half in-camera and half in-post for unusual looks. This gives you some flexibility in post yet also "bakes" the look into the original.

For example, for a blue-ish day-for-night scene, make it slightly blue and slightly underexposed, but not as blue nor as dark as you plan to make in in post.

If you don't do anything, the problem is that the editor and director may spend months looking at the "normal" image and fall in love with it, so by the time you color-correct it, they won't let you do what you planned on doing with the color.

 

[Zagorchinov]

This is great advice for me, thanks Mr. Mullen.

And most important, thanks for the tip about directors and editors falling in love with certain image, I'll have this in mind.