Monday, August 31, 2009

Event photography outdoors at night (sort of)

Our toddler celebrated his birthday at the Rainforest Cafe. It was daytime and indoors but may as well have been outdoors at night for photography purposes. If you haven't been there, it looks like a scene from Raiders of the Lost Ark: rock-like walls, tropical plants and vines, rainforest creatures climbing all over walls and ceilings, shafts of light here and there like sun streaming through the thick canopy of a rainforest, complete with thunder and lightning.
From a family photography point of view, there are many opportunities in this setting - dramatic and colorful lighting, interesting backgrounds everywhere you turn. The challenges were equally diverse: high contrast inconsistent and often dim ambient light, not many surfaces to bounce from.
My objectives were: highlight the ambience of the place (given that the location was an important element of this party), emphasize the fun we had at the party, and as much as possible to make people look good.
In this kind of setting I would never trust my camera in the 'auto' mode. Otherwise, people will have the deer-in-the-headlights look and the background would probably look black.
This is how I chose my controls / settings:
1. Because it was too dark for an ambient-only exposure, I used flash. I took the flash off-camera to control the direction and make the subjects look more three-dimensional. I also gelled the flash with 1/4 CTO because: the light from a flash is usually a bit bluish, people look better in warmer light, and it matches the warm-looking ambient light better. After thinking a while, I chose to use the direct flash instead of a handheld umbrella because it would be too tight to move around with the handheld umbrella. Because light conditions were inconsistent and were changing rapidly, I set the flash on TTL (as opposed to manual).
2. To preserve the ambience, the exposure had to be sufficient to show the ambient light. However, if the exposure is set exactly for the ambient light, and the subject has just as much ambient light as the background, then there might be flash blur like this (sometimes ok for action shots, but usually not ok for static shots). I thus underexposed ambient light by -0.7 stops through exposure compensation. The underexposed background also creates subject-background separation.
3. I chose matrix metering because the light conditions, though inconsistent, were evenly distributed. "Consistently inconsistent." I didn't think there was anything present that would fool the matrix metering.
4. I wanted to use the fastest shutter speed possible (reminder - I'm using TTL) to further minimize flash blur. I thus chose the widest aperture on my lens (Tamron 28-75 2.8) by using aperture priority, and choosing 2.8. I also set the ISO to the highest decent-looking ISO for my camera, which was 800 ISO. Note: noise shows up much more easily in shadows (of which there were plenty at the location). If there's enough light, even 1600 ISO looks acceptable.
5. In aperture priority mode, the slowest shutter speed that the camera will choose is determined by the flash shutter speed setting (I don't know the Canon equivalent, but IIRC there is one for Canon as well). By default for Nikon, it's 1/60, which was too fast for the ambient to register at f/2.8 and 800 ISO, so I decreased it to 1/15, based on test shots.
6. I took test shots for the flash as well. The flash was too strong for my taste, so I adjusted TTL by -0.7 stops. I also used the wide angle adapter for a couple of reasons - first, I knew I would take some pictures of groups of people, and they would be more evenly lit when the flash beam is wider. Second, the decrease in flash power from using the wide angle was not a problem (because ambient was dim). In fact, the issue is the opposite -- at f/2.8 and 800 ISO and flash directly aimed at subjects, I was close to requiring less than the minimum flash power, risking flash overexposure. Using the wide angle adapter effectively 'decreases' the flash power, making flash overexposure less likely.
7. Because it was dark and I didn't want people to blink from the preflashes, I used the SG-3IR.
Based on these settings, these are the results I got.

Although I was using slow shutter speeds (1/30 or slower), most shots came out reasonably sharp because the subjects were being lit only by flash (I underexposed ambient by -0.7 stops). In effect, I was taking shots at the shutter speed of the flash duration (around 1/10,000). In a few shots, the ambient light was bright enough that there was flash blur (like this). I didn't notice the flash blur when I was looking at the LCD. If I had, I would have reduced exposure comp further for those shots. As for the background, the slow shutter speed wasn't a problem because it was disguised by the shallow DOF of the wide aperture anyway.
I think the results are ok. A bit underexposed. If I had to do it over again, I may have gone with -0.3 stops for the TTL instead. To reduce contrast, perhaps I should have used the pop-up flash as fill (though I would risk more blinking shots). In that regard, I'm wondering how much better a ring flash would work as fill (a la Strobist David Hobby). I also would have liked to take some shots with the handheld umbrella for variety, or clamped it somewhere (which I've never tried before).