White Balance at depth
Posted 15 November 2012 - 03:16 PM
Keep Blowing Bubbles,
Posted 15 November 2012 - 07:22 PM
There are many ways to do WB, I've done a whole bunch of variations, including aiming at the sand that's roughly the same distance to your subject, to aiming at the sun from the depth you are shooting. One way I found to work pretty well is to find an old picture or video one shot at certain depth that was not white balanced, aim your camera at a spot that you think should be considered neutral white/grey and set white balance on it and save it in memory. You can even search the interweb for pictures that were not corrected and do WB on that. You can then aim the camera at the pix again and see how a corrected image would look. With this technique, you could perform trial and error on different part of the image until you got what you think is a good color balance.
Posted 15 November 2012 - 08:22 PM
Posted 16 November 2012 - 01:29 AM
My husband found something on this forum a year ago or so about setting the white balance on brown sponges in the ocean. Any help or suggestions would be greatly appreciated.
That would be me who suggested "brown" corals or sponges.
There are two related problems in play with these Sony camcorders with white balance when underwater.
1. Lack of light to do a manual white balance (MWB)
The 550 needs a lot of light or the MWB just blinks at you...
Two options: add some light or MWB off the sun. If you prefer ambient light, you might try the second approach. The most light is coming straight from the sun, so you can try pointing the camera upwards at the sun and do a white balance off the sun. This might work. I've never had much success.
Don't use the red filter. It does not add red. Just reduces green and blue = less light -> MWB won't work.
2. Camcorder over-reacts to the absence of red
Some Sony camcorders seem to have this problem, especially the 550. If you do a manual white balance off something white or neutral, the camcorder can't find enough red so it tries to boost the red channel. It must be increasing the "gain" on the red channel. The end result is ugly red fuzzies floating all over the blue backgrounds. The solution is to do the manual white balance off something that already has a lot of red in it, like a brown sponge or coral. Maybe pink skin. But, if there is not enough light, you are back to the first problem.
One solution is to take down a small bright light like the Sola 1000 or a focus light. Shine that on a brown coral and use that patch of light as part of the MWB subject area for the manual white balance. It wont be perfect, but, if you can find an optimal balance so that you have just enough artificial light to help the camcorder do a MWB, without overpowering the ambient light, you will get closer to a better white balance than just shooting on a "daylight" setting and fixing it all in post. I became quite skilled at this balancing act with the 550.
Since then, I've moved on and now use the Canon XF100 underwater. One great XF100 feature is 4 preset WB settings. I just step through these until I find the one closest to the situation.
1 = Daylight (close to the surface)
2 = 6500 kelvin (5 meters to 15 meters)
3 = 7500 kelvin and set to reduce blue
4 = 8000 kelvin and set to reduce green
These days I rarely do anything other than the slightest tweaks in post.
Posted 17 November 2012 - 05:04 AM
Posted 20 November 2012 - 01:53 PM
This is what I struggle with. Maybe because the water is further away than the main subject matter.
Posted 20 November 2012 - 05:11 PM
I remember that purple color well from my CX550 days.
My theory is that some bright spark in Sony decided that, if one of the RGB channels was low, the camera should automatically boost the gain on that channel. UW, of course, that channel is red. Hence that ugly purple color and, if you look closely, dancing red fuzzies in the blue backgrounds. Remember that the camera is programmed to try to WB so that white is white. And that is impossible underwater. There is no white because red is missing. There is only blue-green.
What I used to do below 15 meters was find something with some red in it (rust, coral, skin), shine a video light on some of it (about half coverage of video light and half coverage of ambient light), and try to find a WB that compensated for some of the ambient light but did not cause that purple. I learned to see on the monitor when the camera was trying to push WB too far. If so, try again with more video light. Of course, this can be a bit time consuming and frustrating. After a few times, I learned how to get it right in a couple of attempts. Then I'd leave it unchanged for the rest of the time at that depth range, only re-balancing when I got back towards the surface.
Edited by peterbkk, 20 November 2012 - 05:13 PM.
Posted 20 November 2012 - 05:48 PM
Posted 20 November 2012 - 10:26 PM
Posted 21 November 2012 - 04:48 AM
Looks like that camera & conditions needs a filter more in the yellow-gold-orange range of the spectrum than the regular blue water filters. You could maybe try to get one of those, or experiment with lighting gel. Or try manually white balancing on something in the pale-purple range.
I think that would just make it worse. The 550 needs a lot of light and at least some red to get a suitable white balance. Believe me, I tried dozens of techniques and settled on the one that works: find something with some red in it (rust, coral, skin, pink fin), shine a video light on some of it (about 50% coverage of video light and 50% coverage of ambient light), then trigger a MWB. Check the result in the monitor. If it looks about right, leave the MWB at that setting for the rest of the dive at that depth range. If it looks too purple, try again with more video light and less ambient light.
Posted 21 November 2012 - 05:34 AM
http://www.cerella.fi for the Underwater Photographer and Videographer