Monday, July 7, 2014
Day 78, Learning 78: Low Light's Forgotten Variable
One variable in low light photography is rarely-- if ever-- mentioned. I've avoided discussing low light photography because the subject is thoroughly tutorialized on the web. And the theory and advice is fairly basic: essentially, open your aperture as wide as possible and increase your ISO until your shutter speed is sufficiently fast to eliminate blur. Of course, we're not talking about working with flashes, night time landscape photography, or image editing, simply available light photography.
Then yesterday I saw a video tutorial on the subject, and after the instructor took a number of demonstration shots, he said: "the only thing I'm not happy with is my angle of view so I'm going to switch to a zoom lens." He did not say that he was manipulating the fourth variable in low light photography. Frankly, I don't think he understood that he was doing so.
The reason I say this is because he was already shooting hand-held at f/2.8, ISO 3200 (ugh), and a shutter speed of 50. His lens was a 28-70mm. The old rule of thumb is that your shutter speed should be equal to or higher than the millimeter on your lens to avoid motion blur. This is truly a "rule of thumb." Some people have incredibly steady hands. Or shaky ones. As lens vibration reduction technology becomes more sophisticated, we can shoot at lower and lower shutter speeds. But while the exact shutter speed may differ from person to person, what doesn't is the relationship. The longer the lens, the faster the shutter speed needs to be. He had already identified 1/50th of a second as the slowest he could shoot; in reaching for his zoom he'll either have to increase his shutter speed (and thus is already painful ISO) or accept blurrier images. Or grab his tripod as well.
The "forgotten" variable in low light photography is focal length. When shooting hand held, don't just reach for the fast glass, reach for the wide one as well.