Colour casts

[Duck_Pond]

I seem to be struggling with colour casts on some images lately, such as the magenta one on my kingfisher shots (bursting out the water) and blues on shots of birds by the coast.

What's the best way to address this problem? I know it can be done in the RAW editor and in Elements, the latter having an auto feature that sometimes works but is very much hit and miss.

I find it difficult to look at an image and see the problem straightaway, and it often only shows up when I've had a sleep and look at the image again, say on my web gallery.

Any help would be appreciated!

[Steve]

I'm not sure how to solve it, but I can say I also find it difficult to judge a colour cast and get it right first time - I often look at an image a day or two later and realise that the colours aren't quite right.

[mjmw]

An easy way to find colour casts - look at an area that should be white (RGB values of 240-250, not 255) and check all three values are the same by passing the mouse cursor over it. Note that this will also show any 'real' colour casts from low sun etc. You can also use a neutral grey area (but more difficult to find unless you have a colour chart or grey card in the image )

For example:
R = 230, G = 230, B = 245 indicates a blue cast
R = 245, G = 235, B = 235 indicates a warm image - maybe from low sun or too much yellow in the colour balance
R = 245, G = 230, B = 245 indicates a magenta cast (opposite of green)
R = 242, G = 243, B = 241 indicates there isn't really any colour cast - the values are close enough

I use the white balance sliders in Lightroom to get the colours almost right and then tweak with curves in Photoshop.

[Steve]

Nice one Mark, I've just had a go @ that in Raw Therapee - seems to work very well!

Cheers!

[Duck_Pond]

Cheers Mark - will revisit some of my Bempton shots and see what I can do.

[Colin]

Here is an easy way to correct colour castes that takes a lot of the subjectivity out of it. Although it looks a little long winded, once you have done it a few times, it can be completed in around 30 seconds.

1. Duplicate the layer and highlight as the working layer.
2. Go to Filter> Blur> Average. The overall cast will now appear as the duplicate layer.
3. Ctrl + I. To invert the colour cast.
4. On the layers pallette, change the blending mode to Colour. It should now look black & white.
5. Reduce the opacity from 100% down to around 10% as your starting point.
6. Finally tweek the opacity up or down a little until the picture looks ok. Generally between 10 - 20%.
7. Flatten image and saveas a duplicate.

By establishing what the caste is and using the exact opposite of that cast to counter it, you only have to use a little judgement regarding the strength of the correction needed.

Colin

[Admin-John]

Interesting tip that one Colin, must give it try!