Dear Sir/Madam, I am a Police Scenes of Crime Officer. I occasionally have to attend the scene of a fatal road traffic accident at night. I have been trained to photograph the scene of an accident by what we call painting the scene by electronic flash light. Using for example a couple of Vivitar 285 flashes and because of our experience we receive excellent results. When we start to convert to Professional Digital Cameras, will we still be able to take photographs at night using the aforementioned technique or will we have to use another technique? Thanks. Marsh.

-- Marsh Smith (msmith@ibl.bm), January 14, 1999

Answers

Hi Marsh- Interesting application! Unfortunately, the short answer is that you're probably not going to be able to do this with a digital camera (unless you're awfully quick on the draw). The problem is that the sensors in digital cameras accumulate "noise" over time, even when they aren't exposed to light. Better-quality sensors can stretch the exposure time considerably, but I think the absolute upper limit is probably on the order of 10-15 seconds or so. Take this with a grain of salt, as we haven't tested pro cameras here yet, and their maximum exposure times could be longer. The consumer cameras we've tested seldom have time-exposure settings beyond a couple of seconds, and even at that level, they're getting pretty noisy. Pro cameras almost certainly do much better than this, but I don't know by how much. Thus, if you can get the whole scene "painted" in just a few seconds, you'll be ok, otherwise not. (Perhaps by having several flash units, and several people, to get the exposures done in a short enough period of time?)

-- Dave Etchells (web@imaging-resource.com), January 23, 1999.