Why do we white balance?

So here is a question to some of you more advanced shooters.

Why do we insist on white balance? What purpose does it serve?

As closely as I can tell, the main purpose of white balancing a video camera is to prevent the camera from over saturating and clipping any particular color channel. Since we are most likely to lose reds first when underwater, that is NOT the channel we'd be most likely to clip. Likely it would be blue. And in rare cases, maybe green.

So, knowing this, if we could somehow shift our cameras so that the blue sensors somehow were less sensitive, or registered colors less prominently, we might be able to get away with not white balancing the camera at all. This is NOT to say the image would be "accurate" when we got back to the edit bay, but we'd have preserved all information in each color channel even if it was not in the correct proportion.

My camera, like many others, has a chroma phase which does this very thing. I am able to shift my camera from under saturating reds, to under saturating blue. In general, I set my camera to under saturate all colors. I purposely try to get a nearly pastel soft image out of my camera. This tends to keep my blacks more noise free, even in lower light, it tends to keep me from clipping whites, and I have a very "flat" image that I can manipulate in many ways. Shifting color in camera seems a natural extension of this idea.

Have any of you tried this underwater? Or would any of you be WILLING to give it a shot to see what you come back with? I am somewhat limited in that my camera for underwater shooting does not have these adjustments. Only my topside camera does. I am really curious as to how this might work.

-P

Personally, I prefer my colours pretty saturated - especially the macro stuff, so i would be reluctant to clip the sensitivity of any of the colour channels. The main reason I white balance is to reduce the time spent in post and a blanket setting won't work because every shot is different. Every meter you descend, every cloud that moves overhead, and the distance betweeen your camera lights and the subject all greatly affect the colours your camera will see which is why we have to manually set the white balance so often.

So here is a question to some of you more advanced shooters.

 

Why do we insist on white balance? What purpose does it serve?

 

As closely as I can tell, the main purpose of white balancing a video camera is to prevent the camera from over saturating and clipping any particular color channel. Since we are most likely to lose reds first when underwater, that is NOT the channel we'd be most likely to clip. Likely it would be blue. And in rare cases, maybe green.

 

So, knowing this, if we could somehow shift our cameras so that the blue sensors somehow were less sensitive, or registered colors less prominently, we might be able to get away with not white balancing the camera at all. This is NOT to say the image would be "accurate" when we got back to the edit bay, but we'd have preserved all information in each color channel even if it was not in the correct proportion.

 

My camera, like many others, has a chroma phase which does this very thing. I am able to shift my camera from under saturating reds, to under saturating blue. In general, I set my camera to under saturate all colors. I purposely try to get a nearly pastel soft image out of my camera. This tends to keep my blacks more noise free, even in lower light, it tends to keep me from clipping whites, and I have a very "flat" image that I can manipulate in many ways. Shifting color in camera seems a natural extension of this idea.

 

Have any of you tried this underwater? Or would any of you be WILLING to give it a shot to see what you come back with? I am somewhat limited in that my camera for underwater shooting does not have these adjustments. Only my topside camera does. I am really curious as to how this might work.

 

-P

Personally, I prefer my colours pretty saturated - especially the macro stuff, so i would be reluctant to clip the sensitivity of any of the colour channels. The main reason I white balance is to reduce the time spent in post and a blanket setting won't work because every shot is different. Every meter you descend, every cloud that moves overhead, and the distance betweeen your camera lights and the subject all greatly affect the colours your camera will see which is why we have to manually set the white balance so often.

If you are trying to reduce the time in post, then I certainly see your point. My thought, and perhaps it's just because of my background, is that I'd rather come home with workable footage, rather than try to get everything perfect in the camera and risk clipping chroma or luma channels.

I can ALWAYS increase saturation in post, and do it very cleanly. I can easily stretch blacks, and adjust colors shot to shot. In fact, if you stop your camera between shots, it will capture this way.

I guess I am more comfortable editing in post, than editing in cam. But you guys are probably WAY better with your cameras than I am!

Yes we can fix it up easy on the puter now days but remember the camera is doing it before it gets compressed. Once on the tape it is compressed.

It's just like adding colour to a jpeg picture after you have taken it.

Video is not RAW (unless you capture uncompressed 4:4:4 via HD SDI) whereby all data are kept lossless. When you do not WB, that chroma setting is compressed into data, after which color grading is doubly hard and more painstaking to get the right chroma saturation without chroma noise.

WB shift works by shifting what the AWB sensor thinks is proper balance to more blue or red, but still within the WB range. That works if there is enough light/chroma contrast for the WB sensor and DSP to register. Often you will see AWB go green as it is not programed for u/w conditions. Some AWB sensors are good enough to adjust with a color filter. I've always found the AWB sensor on the Canon HV series to be excellent for that. Sony somewhere misses the boat.

Interesting thoughts Drew. Although I'll disagree that Video is not RAW. It can be, but it usually is not. At least not within the paygrade of most of us!

That said, if the chroma is not getting clipped, why should it really matter. If we assume for a moment that we are in RGB space, and we are recording an image that has chroma values that all fall between 50 and 190, it would see there is quite a lot of latitude to play with later. However, in that same color space if we are capturing data with readings between 25 and 220, we are certainly not going to have much room to work later. This was my reasoning for desaturating in the camera. If you are going to shift in post, you certainly don't want to venture near clipping levels.

I was not necessarily speaking of WB shift. I absolutely HATE AWB. It makes posting footage such a pain. I'd rather have a white balance that is constant, but incorrect, than to have a moving target like AWB offers. Maybe the Canons is better, but working with Sony footage has me pulling my HAIR out!

Good discussion so far. Anyone else want to chime in?

Of course a constant WB setting with or w/o filter is best. Most major productions do not use MWB/AWB because they are concentrating on luma and the gamma curves/LUT. Which is why you see a lot of blue dominated stuff for wide angle, due to the difficulty and extra work to get it right. It's also an esthetic look that some prefer.

Before this denigrates into a discussion in post color correction you just have to try color correcting monochromic video to see how much difficult it is to get the correct color. There are a few threads in the post subforum about this. MWB helps to alleviate such problems to an extent.

i really hate trying to colour correct deep manta footage from murky days.. man, i can't do it.. so grainy...

so that is one reason i mwb, i suck at post and i never go deeper than 15m anymore...

I'm with you on that one Mike.

Thats why I changed NLE as it could do it better.

Just get the WB as close as you can is best and then touch up on the NLE.

Even hi end $$$ HDCAM's compress the footage as it goes to tape a tiny bit.

All HD formats are compressed somewhat. Even HDCAM SR at HQ is 880mbps vs 1492mbps of uncompressed 4:4:4 HD.

Agree with Josh... saves the pain in the arse of post. Also I reckon when you white balance UW it makes you hold back for a second check the colour, exposure, framing etc.

What are you saying Jonny? You don't frame while you shoot?

Doesn't everyone just wave the camera around and hope for the best???

Sometimes I just get carried away an need to stop spend 10 secs and think about a few things (which hopefully are to do with filming not the chick in front who looked great in a bikini! )

I'm definitely not in the league of everything is instinct.... wish I was though.

J

The color correction bit has been split to :

http://wetpixel.com/forums/index.php?showtopic=23947