RAW images & Correction filters

[dleepenn]

I have been using a Canon 10D in a Jonah case for a number of years (currently for sale on ebay item# 280107368353), and have shot RAW mode to allow for more substantial white balancing of images. I now am shooting a 5D in a Subal housing and am shooting all RAW mode images.

One of the problems that I have is trying to recover the red channel when doing color correction for available light. Here is a sample image from Indonesia:
http://www.dlpco.com/2006Indonesia/_mg_6704.htm
This was taken at about 30 feet. When I look closely at it, I can see red noise. The problem is how to improve this given the need to push the red channel heavily during the development from RAW to jpeg.

Do any of you use correction filters? I have a couple of sources but have not really done anything yet. In Indonesia, I was diving with another individual using Nikon gear and he got incredible shots (but had dual big strobes).

Lee

 

[Taxgeek]

Magic Filters seem to be popular. I haven't tried them yet, but will in about a week when I go to Indo myself. You still have to manual white balance, and they block a bit of light, but people seem to get good results if it is light enough.

All they are doing though is dropping the green and blue channels to the same (or closer to the same) low levels of the red channel, so you're going to have to adjust your exposure times, but on that shot, you had room. (Alex Mustard, who sells the Magic Filters, did extensive tests on all the possible filter colors and came up with just the right combination of the best ones for UW use. Very considerate of him, I think!)

The noise in the red channel might also be partly due to shooting at 640 iso?

(Great picture, by the way, I love the turtle's position on the table coral). There are some people on wetpixel doing things like completely reconstituting the red channel from the other channels - too technical for me, but I wonder if that would work for you.

 

[jarhed]

I use magic filters w/ my D200 setup and have been very happy with the results in relatively shallow (less than 50 ft) and good light. Manual WB isn't hard, but occasionally a pain to find a good surface to WB on. I should carry a grey card i guess. For the price, it's a nice addition to your natural light setup and when conditions are right, it's great to leave the strobes at home.

Take care,
John