Unique White Balance Problem

[rpcrowe]

I was shooting a turtle in an underwater tank through (I assume) a Plexiglas window. The viewing area was quite dark (which reduced reflections) but, I could not get directly up to the window which was quite scratched and appeared dirty. The tank was lit from above and the water was quite murky. All these factors presented a problem with white balance. I could not use my WhiBal card and there was no portion of the image which was a neutral color. This is what the image looked SOOC...



I worked on the scratches in Photoshop and I adjusted the white balance with a "guestimate" factor.

This is the result...



I am wondering if there was any other, more scientific way to adjust the white balance in a case like this...

[NigelD]

I don't know how scientific this method is, but I opened in CS6, duplicated the BG and my first thought was to find put how near an 18% grey the image was. I went to filter/blur/average and then did a levels adjustment on the resultant colour but only to set the grey point. I then discarded the "average" layer and came up with an image that had some green on like yours, so I sampled a grey near the edge of the shell and then painted over the green bits in colour blend mode

[IMG][/IMG]

[yauman]

Give this a try - I have had some success with picture which I don't know the correct WB and can't find a reference patch but which obviously look like there's a color cast over it. This is done in PS.

1. Duplicate the image to another layer (call this ImageCopy)
2 On the ImageCopy layer, apply an Average Blur (Filter>Blur>Average Blur)
3 Apply enough blur, ie remove enough details so there's no distinguishable "lines" (5-10 pixels)
4 Invert the image (Command-I on Mac)
5 Set the Blend mode of the layer to "Color" blend
6 Play with the Opacity slider still it looks right to you.

[Shadowman]

That's an odd shooting environment, you have the WB of the room you are standing in, the WB of the interior of the tank, and your eyes are also probably influenced by the reflected light coming from the bottom of the tank.