Trompe l'oeil digitale

I was having coffee with a photographer friend today and in the course of discussing light (yeah, this is what photographers talk about when we get caffeinated together) I mentioned how changing your camera's color temperature setting and putting a complementary filter over the flash head will keep the subject balanced correctly and let ambient background light turn crazy colors.

There. Did I lose all the non-photo geeks? No? Still some here? Okay, quick and hopefully painless:

Different kinds of light have different colors. We don't see this because our brains correct things to make light look mostly "white" to us, but film (and digital cameras) are not as smart as our brains. You've seen photos taken under fluorescent lights that look green, or under incandescent lights that look orange, right? That's different kinds of light having different colors. We can tell digital cameras what kind of light we're shooting under so our photos come out with correct colors, though, and that means we can set our cameras to accurately record colors under fluorescent or incandescent light, for example.

We can also change the color temperature settings on our cameras just for the hell of it.

The "tungsten" setting on your camera adjusts for light it thinks is too orange. So it corrects for this by adding a bunch of blue. Under orange incandescent light, that makes everything look normal. But what happens if you set your camera to "tungsten" and you shoot in daylight? Everything looks blue.

Except (and this is the cool part) if you throw some tungsten light in the photo somewhere. It will appear normal, right? Tungsten light OR a flash filtered orange (to make it look like tungsten light) will appear white.

I tried to explain this to my friend (I thought everyone knew this) and I knew I was making some sense but not a ton of sense. So what better way to teach than to show, right?

My camera was in the car. She had her Canon G9 with her. Great! I can set the camera to shoot tungsten, and light coming in the window will turn blue. But what about the cool part, the part where I throw some orange light in there and it becomes white in the photo?

I looked in my backpack. And yes, I had a blank CD in a clear orange plastic case. Bingo.
Gear for today's impromptu photo class.

So I set the camera to shoot tungsten & took a photo of her with the window in the background, while holding the clear orange corner of the CD cover over the little flash. That way daylight turned blue in the camera and the flash illumination that fell on her appeared to be white.

It was her camera so I don't have the pictures. So I duplicated the approach at home, by shooting a little bronze statue of a bodhisattva that I had placed near a white wall by a window. So the light falling on the wall is daylight. And when I light the statue (not the wall) with a flash, it looks like this:
Shot on "daylight" setting, so both flashed statue and wall appear correct.

Then I set the camera to tungsten (which means daylight will look blue in the photo) and added an orange filter over the front of the flash (so the camera will see that orange light as correctly balanced) and was careful to aim the flash so no light got on the wall.
Shot on "tungsten" setting, with an orange filter over the flash, so flash light appears correct and daylight appears blue. Blue daylight. Did I just blow your mind?


More dramatic. And easy to do. Note the color of the little bronze statue is the same in both images. The only photoshop work I did with these images was to make sure one was set to be correct for being shot in daylight and the other was correct for being shot in tungsten. And I cropped them smaller for the web. That's it.

This isn't an amazing new trick, it's an old simple one. I've been doing stuff like this since I was an intern (using tungsten-balanced film because digital? What's that?) at newspapers in Florida. But it was new to her, so I thought I'd share.