2 ?s about using gels with flash

When using a gel with on camera flash to balance flash and ambient lighting.

Do you use the custom white ballance or just choose one of the settings on the

camera like tungsten or fluorescence?

If you do a custom white balance do you take the picture to be used for the

white balance setting with or without the flash and gel?

Thanks

A custom white balance will almost always be more accurate than a preset white balance

setting when it really counts... particularly under flourescents, which can be all over the

place.

In creating the custom white balance, I'd do it with the flash and gel.

"In creating the custom white balance, I'd do it with the flash and gel."

And I'd shoot raw as well.

If the flash gel is well matched to the ambient lighting, it should make no difference whether you use an ambient shot with no flash or a shot with the gelled flash as the basis for white balance. However, it can be very difficult to get an exact match since the flash spectrum is not continuous, and the spectra of some kinds of artificial light are distinctly non-continuous, so it is usually best to use the lighting of the actual shots.

http://members.misty.com/don/spectra.html

Of course, you also need to consider whether artistically you want to have an overall balance that is slightly warm or slightly cool rather than being strictly "correct" white balance. You can achieve that by using a "warm card" rather than a true white/grey card as the custom white balance target.

http://www.studio1productions.com/warmcards.htm

You can achieve similar effects by making the custom white balance shot of a white/grey target through a suitable complementary filter which is removed for the actual shots, or correcting to true white without a filter, and then using a filter to add the white balance offset. These methods have the advantage over adjustment in post processing that they can be made consistent between different lighting situations more easily - something that can be very important when shooting a film where elements of a scene shot on different days need to be intercut.

Shooting RAW gives more flexibility to make adjustments to taste in post processing, but at the expense of repeatability under differing lighting conditions.

Get yourself a set of gels for flourescent, they can be a real pain. The compact ones are rather inconsistant. It may help to set your shutter speed that's harmonicaly related to the line voltage (1/15, 1/30, 1/60, 1/120 assuming a 60Hz line voltage) to be as consistant as possible.

If you try setting your white balance at say 1/200 shutter speed you may find your white balance off from shot to shot (with flourescent lights). It's more of a problem with older magnetic balasts than with the newer electronic balasts.

"However, it can be very difficult to get an exact match since the flash spectrum is not continuous..."

Typical photographic flash tubes are usually operated so that their behaviour is very close to that of a greybody source, ie they have a continuous spectrum. This can't be said for all xenon flash tubes, or all conditions of operation.

Best,

Helen