Removing colour cast

[Conk]

I would like to find out the best way of removing colour cast from subjects after shooting against a chromakey green backdrop. I'm using Photoshop CS.

[Doug Nelson]

If there's green reflected on the subject from the greenscreen, the purpose of the greenscreen has been defeated. Not that this helps you now

[Flora]

Hi Colin,

You could try these great ways for minimizing/removing your colour cast:

Quick Fix for Severe Colorcast

Another Quick Fix for Unwanted Color Cast

Quick color cast correction

[Conk]

Thank you very much Flora. The colour cast I'm getting isn't as near severe as the examples I've seen in those tutorials but should do the trick. It is just like an inner fringing in small areas of my subjects. I've been able to reduce it enough that I can print an image and it looks fine but when viewed in the sunlight, all the defects jump out, such as the green cast.

[Flora]

Hi Colin,

glad I could help!

But if you are still not satisfied with the result ... if possible, you could post the image or part of it ....

[Chip Hildreth]

Sounds like the problem Doug described. I've had it with a chromakey blue BG.

If the subject is too close to the background you get reflected light from it that diffracts around the subject... makes the colored fringe you describe. It's also a problem if they are standing on colored seamless paper but the reflections drop off before somewhere below knee level in most situations.

It gets down to distance from the reflection source. You want the reflections to fall off (inverse square law thing) before they reach and register on the subject. You can use white reflectors to backfill areas where the mainlight doesn't overpower the reflections.

For future shoots you can put some space between the subject and the BG. I've had better luck suppressing the BG reflections by lighting the paper above the subject's head with a single, bare bulb strobe placed close to it. I've gone to a white BG lit the same way when I need to knock the subject out... selection in PS is a lot more controllable as long as there is good lighting contrast between subject and BG.

chip

[Conk]

Thanks chip. I have tried moving the subject away from the bg but maybe not enough. I also think that moving my lighting a bit closer to my subject and try not to light the bg so much.

Flora, I didn't post an image because the colour cast isn't as visible when displaying it at a low resolution web displsay. It is important that it doesn't show up on my prints. I've yet to try the tutorials but will be posting as soon as I get a chance. Thanks again.

[Leah]

Colin, Sounds like you have things in hand, but you could just post a cropped patch of the photo showing the problem at full resolution, rather than the whole thing at lower resolution.

[Chip Hildreth]

Slept on it and I have a couple of minor ideas.

Is the fringe in places like (assuming human subjects) the armpits, between fingers, under ears, etc.? If so, your reflections are probably coming from below. You can feather your mainlight and reflectors to illuminate the subject only and miss the BG underneath them. Overpowering them by moving the mainlight closer will work but then you get the falloff problem where there is three stops of range from nose to ear... you know what I'm talking about.
You could also throw a fill light in from below but if it's off center you still have problems in the nooks and crannies on the shadow side... plus, you probably don't want to use lots of lights.
You might try black masking any BG material that isn't in the photo if the subject is relatively stationary just to suppress all the colored light flying around the room.
Another question... what's the purpose of the chromakey green?

Aside, I checked your website; the portraits are nice. I've not done any dog photography but regularly do retouching on show dogs for ads; it's fun work.
It's the aircraft I really like though; I used to be into aerobatics in a big way, owned a Pitts S1S... sold it about eight years ago and haven't flown since.
The shots are just like what you see in 'Aerobatics Today' and airshow galleries... very cool. I like the Sukhoi.

Good luck.

Chip

[Conk]

Well, I'm still having a problem removing this cast and thought I'd post an image that clearly shows the green cast on the dogs front leg. If you look close enough it is also apparent in other area's.
After I replace the background with another digital image, the green cast is visible in areas on the dog. This image shows the dog lying on the chroma key backdrop but most of my images just have the animal on a table using the Chromakey in the background and not beneath. I just used this image as an example of the colour cast.

[Conk]

Here is another image with the back ground replaced but the green colour cast still visible on the dogs head.

[roger_ele]

Hi Colin,

This is not the most elegent solution - but in this case I think it might be the simplest ...

create a new layer and change it to color blending mode. pick a small paint brush, sample color from the dogs hair good and paint the color where you need it. now you can knock out the background with no worries ...

Hope this helps,
Roger

[imrtun]

http://img24.exs.cx/img24/3956/Dog.png

Still trying to remember what exactly I did, nice picture by the way.

• Duplicated the background layer
• Used the custom hue replace tool at 85 percentage and painted over the green parts of your image
• Created a new layer with green as the blend mode
• Created a new layer with blue as the blend mode, may also have painted over the blue parts with the hue replacement tool again same settings.

I hope that was right! I will try to keep a closer eye on what I'm doing in the future I would be happy to email you the cpt/psd file so you can see in more detail what it was that I did.

EDIT: I also noticed a kind of blue tinge on some parts so I have fixed that also, http://img93.exs.cx/img93/3956/Dog.png

[Conk]

Thanks Roger. That does work well. It is fast and easy. Something I could do after the image is knocked out.
imrtun, I have never heard of the custom hue replace tool. Could you calarify that?

[imrtun]

It's a tool from Corel Photo Paint