Saturday, May 23, 2009

Exposing manually for birds

Royal Tern, manual exposure, 1/1250, f/7.1, ISO 200, Canon 20D and 400/5.6

You'd think that when shooting wildlife in action you would want as much as possible automated, but exposure might not be one of those things.

When I recently started attempting bird in flight shots, I was shooting in Av mode. This consisted of pretty much moving the aperture between 5.6 and 11 depending on how much light I had, in order to keep the shutter speeds up. But, the results were frequently not particularly good. As fine a metering system the current cameras have, there isn't much that can be done in scenarios like small white bird against black background, or black bird against bright blue sky... one has to dial in exposure compensation back and forth constantly and hope that with experience it'll be "close enough" to save in post processing.

Often though, the exposure was just too far off and I ended up with noise in the dark areas or blown out highlights that even RAW files wouldn't retain. So I decided to try shooting in manual mode. What I found was that when shooting in relatively consistent light this was a far superior method as the background and subject and their relative brightness no longer was an issue; the amount of light falling on them did not change so why should the exposure? Indeed this was a lifesaver for me--I could shoot a Pelican in the water and two seconds later a Royal Tern against a white cloud and both would be exposed properly. In any other mode it would have required some experienced--and fast!--fiddling with exposure compensation to accomplish. Seemingly counter-intuitive, manual mode in this instance actually makes things EASIER.

Royal Tern, manual exposure, 1/1250, f/7.1, ISO 200, Canon 20D and 400/5.6

So what method do I use for setting the meter? Well, to be honest it's a fairly crude and basic one. I pick a scene that's in the light I want to meter for, change the ISO, shutter speed and aperture until I find an acceptable combination (for birds in flight I like to stay above 1/1000 shutter speeds) that the camera meter thinks is proper, then fire a shot and inspect the histogram. If the scene contains a good range of tones (some shadows, some bright highlights) and the histogram looks good (as far to the right as possible without blowing anything out -- turn "blinkies" on in your camera review mode to spot that) I'll use this exposure setting until the light changes. Sometimes I'll end up moving things around a bit and getting above or below the camera suggested exposure, mainly in a quest to get as much data in the RAW file as possible (see Expose Right at LL for why I do that.)

Mourning Dove, Av mode, 1/500, f/9, ISO 640, Canon 1Ds Mark II and 400/5.6 with 1.4X converter

Sometimes, though, when the light is rapidly changing, I'll go back to Av mode. This lets me react quickly to an opportunity, and will get me shots I wouldn't get when in Manual mode since I'd have to spend time fiddling with the exposure settings. In Av mode I generally leave it at zero exposure compensation and just dial some in where I gauge that it's needed. No scientific method behind what direction and how much; at this point it's pretty much based on experience.

Hopefully this helps explain why manual exposure can sometimes make life much easier!