Last week, I visited the Idaho School for the Deaf and Blind to photograph their new augmented reality sandbox. It's a cool tool the school has that allows students to immerse themselves in a topographical map. It really makes learning a hands-on experience.
As soon as I walked in I was excited to see all the colors from the projector. The photographer in me was eager to get started, but the realist in me knew there were going to be some challenges.
The first hurdle was exposure settings. The way the light shines down on the sandbox creates a glowing base that illuminates the faces of my subjects. The problem is choosing what to expose for.
Typically you set your camera to properly expose the subject and deal with the background in post, but this isn't a typical situation. If I expose for the subjects, the sandbox will be completely blown out. It will just look like a bright white light with zero detail. On the other hand, if I expose for the sandbox, my subjects will be drastically underexposed.
Because I was shooting in RAW, I knew I could expose for something in the middle and still be able to recover both my highlights and shadows. Camera RAW, for those who don't know, is a type of file you can choose to shoot in instead of jpeg. It collects a lot more data than jpeg files do, which gives you more capabilities in editing. The downside is the size of the files are huge, which eats up a lot more space on your memory cards. I shoot on 16 GB cards and format after every shoot, so space isn't an issue for me.
Camera RAW gives you an extra level of toning. As seen in the screenshots below, I can adjust my exposure level, bring down my highlights, lighten my shadows and adjust the saturation before the image is ever opened in Photoshop. This adds a base layer of toning to correct for mistakes I made while shooting.
I've attached side-by-side comparisons of the same toned photo using a jpeg file and a RAW file. If you look at the hands in the sandbox, you'll notice a lot less detail in the jpeg version. That is because I wasn't able to recover all of the data in that overexposed area.
The second hurdle I had was the inevitable light flickering that would occur with this projector. The simple explanation is lights flicker through different wavelengths at 60hz per second. When combined, the cycles make up the light that we see. This is especially true with fluorescent lights. If you shoot with a shutter speed above 1/60th of a second, you will freeze the light in one of its cycles.
Here are two photos taken in rapid succession that show exactly what I am talking about. These were shot at 1/1500th of a second. As the light cycles through it's wavelengths it shines different colors and exposures on different areas. By combining the two photos (as I have done below) you'll notice the skin tone on the arm in the upper right corner is almost spot on to what it looks like in real life.
If you ever encounter light flickering, drop your shutter speed to below 1/60th of a second (or deal with the headache of color correcting half of your photo). To combat the change in exposure you can reduce your ISO or increase your F-stop. If you are ever dealing with a situation that has intense highlights and shadows and you cannot shoot in RAW, expose for the highlights. It's easier to recover detail from a shadow than a highlight.