Gel for tungsten

Every now and then you need to shoot indoors where there are tungsten light, like big chandeliers at Versailles. To get the proper lightwe often employ flashes, and this is where the problems normally begins, as you can’t color balance your exposures.

Why’s that? Of course the answer is the different color temperatures of the flash – typically daylight, approx 5400 Kelvin – and the tungsten bulbs – typically 3200 Kelvin. A lot more information can be found at Wikipedia.

So why is this post named “Gel for tungsten”? Well, that’s because that is exactly what we do to solve this problem. We use an “CTO” gel, which is orange (CTO stands for Color Temperature Orange) and converts our daylight-balanced flash to tungsten (or incandescent). The CTO gel will filter our flash and turn it into a normal light bulb, as far as light color is concerned. Cool, huh?

CTO gel for SUN

And yes, this is going to be very orange. However when you shoot in a tungsten environment, you need to get your light balanced, i.e. consistent (or the customer isn’t going to come back another day). CTO’ing the flash makes the flash orange, so your flash and the ambient light match. Then you need to set the camera to the tungsten setting (normally it the “light bulb” symbol on your camera white balance knob), which make the camera understand the world you have setup .. all of the lights will appear like daylight.

Temperature variation
Excellent, but then you may notice a few problems .. like .. damn, it doesn’t match or it isn’t consistent all over the room. So why’s that?
Pay attention, this is important. Tungstens are not always as correct in color temperature as we need them to be. A light bulb does actually change color all the time, through aging or just through voltage or current variations in room’s electrical power. You can test this outfor yourself if you have a room at home with a dimmer. Dim the ceiling lamp, and notice the lamp getting more and more red. Its probably almost pure red before its turned off. Yup, life sucks!

But if you know this, you will also know that it is virtually impossible to color balance a room with tungsten lights with just CTO gels. Obviously the same rules apply for fluorescent lights as well.

Typically when you get to your location you’ll notice that lights are dimmed or power’d off, power on or dim to max all the lightbulbs that you need for the scene. Getting that higher ambient light makes gelling easier. If you have a room with mixed fluorescent and tungsten lights, try to turn off the fluorescent. If you have not used flashes, you can use the modelling light, which normally is a tungsten bulb, to increase the ambient light further – do not gel these flashes 😉

Gelling?
So what is gelling for tungsten? The concept is basically to add a color filter in front of our flash to lower its color temperature, so that it match the tungsten lights. Its easy to get good results as tungsten mix very well with CTO gel’d flash, when balanced in your camera. But how do you shoot with ambient light? Never forget that it is the shutter speed setting that controls the ambient component. Balancing down lower with ambient – underexposing – intensifies the color. Balancing up higher evens it out.

So, the tungsten color problem you might not have considered before, is easy to fix and you will now look more professional and your customer will get back another day, for another shoot.

A few facts
The color gel, color filter or lighting gel, is a transparent colored material that is used to color light and for color correction. Modern gels are thin sheets of polycarbonate or polyester, placed in front of a lighting fixture in the path of the beam. Gels have a limited life, and the color may fade or even melt, depending upon the energy absorption of the color.

Gels are available in single 500×600 mm sheets, and 600 mm or 1200 mm wide and 16m long rolls. I use the 1200mm x 16m rolls.

Further reading is found on Wikipedia
Color Gel
Photographic filter
Wratten number
Rosco gels