The Color of Light, and How to Gel a Flash

A whole new world of photography opens up when you begin to use a flash in creative ways.  My understanding in this area was sped along last March when the sole book I brought along on spring break was Joe McNally’s The Hotshoe Diaries. The vivid examples in that book were nothing short of inspiring to me.  I devoured that book, and then looked in other areas to understand how to gel a flash, and the corresponding White Balance setting required on the camera most notably:

Joe McNally Joe McNally’s The Hot Shoe Diaries

Strobist http://strobist.blogspot.com/2006/03/lighting-101-using-gels-to-correct.html

Ron Bigelow’s Blog:  http://www.ronbigelow.com/articles/magic/magic.htm

I’m a chart kinda guy, so I put this one together certainly not so stand in place of these other sources, but to be a guide as you read such books and posts, and perhaps also as a reminder later to quickly consult.

There are three main parts to this chart:

Three Common Scenarios

Camera White Balance Settings (and equivalent Filters)

Color Spectrum

The three common scenarios that I decided to highlight are: indoor with tungsten (incandescent) light, indoor with fluorescent light, and finally, outdoor with the rich light of the magic hour: the half hour after sunrise, and the half hour before sunset. In all the scenarios you gel the normally ‘daylight’ flash to match the ambient light.  And then in the first two scenarios, you tell the camera (with the white balance setting) to move this light back to a normal white light.  In the third case (magic hour) you have the camera on ‘daylight’ because you want to keep that warm light and not change it back to white.

The Camera White Balance Settings part just reminds you how the various white balance settings correspond to the ambient light values (its interesting to see the Kelvin values).  I also included the equivalent filters that were used when photographers were using daylight-balance film and had to deal with these situations.  Not that many of you have experience with these filters (and they were expensive!), but visualizing how they changed the light entering the camera further helps to explain this topic.

Finally, The Light Color Spectrum, lays out the warm to cool light spectrum with many examples along the way.  I’ve listed the more common Kelvin temperature value for each example, but also the less common ‘mired’ value (1 mired = 1,000,000 / Kelvin Color Temp).  I included this because the gels sometime indicate the ‘Mired Shift’ value, and understanding this also helps lock in your thinking here (for example, a CTO gel that coverts a daylight balanced flash to match warm tungsten light, gives a +167 mired shift.)

This whole space was at first a lot more intimidating than it turned out to actually be.  Best of luck in your lighting endeavors!

A Rocky Mountain Joe® Nugget

Boulder, Colorado 2010-01-16

Attribution-Noncommercial-No Derivative Works 3.0