balacing with gels

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stuart anthony

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Stuart
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ok. im doing some products shots using a light table to get a pure white background. My lights are lencarta 300 elite pro's for above table and a canon 430exII placed to eluminate beneathe table, However im getting a slight green cast from the 430exII which i need to remove. what colour gel do i use on the 430exII to balance the light??
I have lightroom so i could desaturate the green but want to get it right in camera.

Many Thanks
Stuart
 
If it's a green cast then logically you need a magenta filter - but nobody can tell you which one, because it depends partly on how strong the cast is and partly on how much overexposure you're creating - the brighter the light, the less cast will be visible, and the less apparent effect the filter will have.

I think the real question is this - why is your flashgun producing a green colour cast?
 
thanks Garry that gives me a starting point to work from.
would it be that im using a very low output setting on the 430exII that gives the green cast, if i increased power from the 430exII would that help to correct the inbalance?
 
I'm not a Canon user and haven't tested your flashgun, but would expect the quenching of the flash at low power to increase the colour temperature quite a lot - I did tests on my Nikon flashgun and found differences of 1000K between min and max power - but the colour shift should be more blue than green.
But to answer your question, yes the colour should be warmer if you use a higher power setting.
 
Probably a stupid question but do you have any green walls or anything blue/greenish the flash light could be bouncing against and causing the colour cast?
 
In theory, the light from a hot-shoe gun will get more blue as it's turned down, and a studio flash gets more yellow. I have also found that some studio heads can also have a bit of a magenta spike at lower powers, which you can take out with the magenta/green slider in Lightroom.

It's very slight, though I wonder if the compounded effects of the two light sources going in different directions at low power, plus maybe the shoot-through surface you're using has a hint of green (or do you have a green carpet underneath?) would be enough to be noticeable.

As Garry says, if you blow it to pure white, then any cast will vanish. But if none of these things works, a gel over the 430EX would seem like the easiest way.
 
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