Sunday, March 11, 2012

Light Where You Need It

I was assigned to photograph "Read Across America" at Learning Ally in Palo Alto during a week-long marathon of reading and recording. The event was to help build a library of audio books for use by the visually impaired and readers with disabilities such as dyslexia. Mimi (the recorder) and Pat (the reader) were from the paper's service area, so these were the two most important volunteers.

When I first arrived, I immediately went looking for a location where they both could be photographed at once. I was pleased to find this work area complete with a window facing into to recording booth and a window overlooking the parking lot. Normally such a window would be a major problem because it would be nearly impossible to balance the bright exterior sun with any form of interior speed light illumination. As luck would have it, the weather was misty and dark, and therefore a much closer match to the output of my flashes.

I now had four exposure areas to address:
  • The inside of the recording booth,
  • The outer office,
  • The window on the parking lot, and
  • The LCD Monitor.
The D7000's initial settings were ISO 200, 1/250 of a second, F 5.6, daylight White Balance. The lens was a Tokina 11-16 2.8. I used 2 Nikon SB-800 speed lights and controlled them using iTTL. The SB-800 lighting the interior of the sound booth was + 2/3 stops, the on-camera commander was set to 0 compensation.

First, there was the recording booth. When I looked inside the recording booth, I decided I could could narrow the beam of my flash and run it stright up to the ceiling. This would hopefully prevent any stray light from scattering around in the background. For the most part it worked, but you can see a little leaked out and lit the top right edge of the window frame. I gelled the flash with the CTO Full equivalent that comes with the speed light because I wanted to give some color separation between the interior and the exterior, should the paper print the image in color. Here's the first test shot.

If you're wondering about the dark, round shadow at the bottom, it's the lens hood. I used the on-camera flash in the commander mode to make this first test. If you see a shadow like this, it probably means that your on-camera commander has been programmed to contribute to the flash exposure, as was the case here. When I saw it, I decided to ignore for the time being, since I was only interested in the interior of the recording booth.

Next, I added an on-camera SB-800 in the commander mode, and put Mimi and Pat into position. After some experimentation, I aimed the on-camera flash straight up to minimize any glare on the LCD screen and the recording booth window. I also closed the blinds a little bit more. Remember that my camera is still set to 1/250 of a second, so the ambient room light is not contributing to the exposure.

You can also see that Mimi's head seems to blend in with the LCD panel, making it difficult to separate her from the background. So for the next shot, I moved her back slightly so that her the blinds would serve as a background for her head.

Now for the trick shot. I asked that the office lights be turned off for two minutes while I made the final photograph. Once they were off, I changed the shutter speed from 1/250 to 1/20, a lucky guess. This increase in exposure time would affect the two continuous light sources: the parking lot and the LCD monitor. I reasoned that the monitor was visually more important to the photo than the parking lot. Here again, is the final shot.

You can see that the parking lot is overexposed, but not to the point of distraction. But the colors on the LCD is now bright and full of detail. While there is a hint of glare (you can see the reflection of Mimi's sweater in the recording booth window), it is pretty much under control.

This was another 15 minute photo, with very little "dead time" in either the front end or the back end. I was glad to be out of there, and I suspect they were too.

By the way: Be sure to pick up after yourself. If you look on Mimi's desk, you will see the dome diffuser from my SB-800, complete with gaffer tape stitches, sitting exactly where I left it.