Novice flasher confused re gels

Hi guys, I'm hoping someone can help me get my head around flash gels.

I've just bought a 430EXII and have been looking at flash gels. One of the principal reasons I bought it was to improve informal shots taken at home under largely tungsten lighting where pop-up flash lead to harsh shadows and also a mismatch in colour temperature across the shot between flash and ambient lighting.

Therefore I started looking at flash gels to balance this. I get the general principal of adding say, an orange filter, to balance out the effect of tungsten, but I can't figure out what manufacturers mean by "converts 5500 to 3200". I understand colour temperatures, but didn't think the colour temperature of a flash was 5500k.

Is this a standard convention for showing the amount of correction? Can someone point me in the right direction?

Hi. I've always thought that my 580 flash and my studio lights are equivalent to daylight, so 5500k would be about right. I've never used gels, never found a need to. Someone else may be able to correct me, but I've always found that if I turn on as many indoor lights in the room as possible and either bounce the flash and/or use a reflector, its not too much of a problem. If you shoot raw you can always tweak the color temp.

It's all pretty much a trick to at least get into the ballpark. I whitebalance my flashes usually at 5900K. If I use a full CTO, I end up setting the balance to anywhere between 3000 and 3400.
If I want to get really anal about things, I'll use a graycard to set the EXACT white balance as a custom WB or in PP. More importantly, I don't want any lights to be yellow or blue-like. Gels are usually best for balancing lights. The most important thing is to prevent flashing while having enough ambient light from tungsten lightsources without balancing your flash. That will give you yellow/orange light mixed with white light, hence, you make your flash more or less the same yellow/orange, and you shift the white balance from daylight / flash to tungsten.

As Hannya said, you'd probably never use this in a studio setup or when you don't have any ambient in your exposure. Of course it does offer some creative uses, like using cold/hot light in the same image.

Another use for it is to make an sky background more saturated. You'll shift the entire thing to blue that way (flash with CTO and camera in tungsten WB).

Thanks Hannya, I do shot in Raw so usually correct a colour cast if needed.

The problem I'm concerned about is the difference in colour between the flash and ambient lighting, you can't correct for one without affecting the other.

It may be less of a worry with a bounced, diffused flash though, but I'd plan on matching the flash to ambient light when possible. Maybe I'm being unduly concerned!

Tungsten lights are around 3200K. Flash is around 5600K. Adding a CTO gel changes the flash color temp from 5600K to 3200K, more or less. This means all your light is approx the same color, and you can do a white balance and have everything look right.

When the scene was under tungsten light I tend to balance it a bit warm, since it did look warm to the eye. Making whites look pure white looks artificial. I have standing instructions with my lab to color correct my work around 500K warmer than standard, I just like it better.

tim wrote in post #8706328
Tungsten lights are around 3200K. Flash is around 5600K. Adding a CTO gel changes the flash color temp from 5600K to 3200K, more or less. This means all your light is approx the same color, and you can do a white balance and have everything look right.

When the scene was under tungsten light I tend to balance it a bit warm, since it did look warm to the eye. Making whites look pure white looks artificial. I have standing instructions with my lab to color correct my work around 500K warmer than standard, I just like it better.

Anyone interested in doing this in-camera, it's pretty simple. First, gel your flash with a CTO to match the indoor tungsten lighting. Then take a grey-card shot with flash, but hold a 1/8 or 1/4 CTO gel over the camera lens (matter of preference as to how warm you want the shot). Then, simply use that grey-card shot to set a custom white-balance.

You'll have a shot where the flash & ambient are balanced, and then warmed-up by a set amount which should keep things consistent across different locations.

Thanks guys. I agree in that I don't usually completely neutralise tungsten lighting because that's how the scene was lit, I've done shots with a grey card to "correct" the white balance and generally preferred things as shot.

OK then, I think I've got it now, in that flash does generally have a colour temp of 5600k which is where I was confused, I though it was cooler.

So I guess it's broadly something like CTO for tungsten, greens for fluorescent, nil for full sun and blues for cloudy conditions. These [with some experience!] will balance flash colour temperature with ambient colour temperature then I can decide in PP just where I want the overall temp to be.

i saw the stuff on planetneill about gelling the flash.
of course, it's a little down to 'taste' but I don;t like the flash to be completely balanced to ambient, for example, some sodium or candelighting.
I think it's nicer to allow some of the actual ambient colour to register as well and looks more natural.

Hangerhead wrote in post #8707358
i saw the stuff on planetneill about gelling the flash.
of course, it's a little down to 'taste' but I don;t like the flash to be completely balanced to ambient, for example, some sodium or candelighting.
I think it's nicer to allow some of the actual ambient colour to register as well and looks more natural.

The problem is, when the colours of the flash and the ambient sources are unbalanced, you'll get inconsistent results depending on the ratio of flash to ambient each shot uses.

If you bounce-flash in a dark area of the room then the flash might be providing 90% of the light, if you move a few metres to another part of the room then the flash might only provide 50% of the light. The first of those two shots will look bluer than the second because the cooler light from the flash makes up more of the light hitting the sensor. When the flash and ambient are the same colour temperature then you can use 100% flash, 100% ambient or anything in between and you will always get the same white balance.

None of the above makes any demands on where you set your white balance point. You will get exactly the same temperature as you would have done shooting ambient only, and you'll have the same options as to how to white balance.