12 September 2005

Digital photography notes

Part 1: time lag of digital cameras

Time lag of a camera has been defined1 as “the interval between the first pressure on the trip button and the beginning of exposure”. Time lags of several models of SLR film cameras (mid-1980s models) varied between 46 and 230 milliseconds 1.

To estimate the time lag of my Olympus Camedia C-5000, I photographed my stopwatch at 10, 20, 30, 40 and 50 seconds2. The picture below shows the results obtained with the focus manually fixed before the start of the test.

The average of the individual time lags (1.1, 0.97, 1.16, 1.03, 1.03 seconds) is 1.06 seconds or 1060 milliseconds. This is huge compared to time lags of film cameras. The time lag is further lengthened if the camera is in autofocus mode as was the case in the test below.

Now the average lag is 1.87 seconds; almost a second longer. Other models of digital cameras probably have comparably long time lags.

You’d be amazed when you realized how much peoples’ facial expressions and body postures or the positions of a butterfly’s wing positions could change in the span of a second. To get around the long time lags of digital cameras learn to anticipate the movements or positions of active subjects and try to press the shutter button a second or two before the anticipated moment. This is harder done than said. Another way to shorten the time lag when photographing a subject whose position relative to you will remain constant is to turn of auto focus and to adjust the focus manually once in the beginning. For example, if you are photographing a distant event, say, a soccer game, you may manually set the focus to infinity, thereby shortening the time lag by about a second.

Finally, if you are photographing a rare event do what professional photographers do: take many pictures, hoping that at least a few will come out fine or just perfect.

1. Goldberg, N. New, state-of-the-art SLRs are impressive, but what about their irksome time lag? Popular Photography. Unknown issue, pp. 72-74, circa 1986.
2. This is, of course, not the best way to take such measurements. The measured time lag also included the time lag between the moment my eyes relayed an image to my brain, which issued the command “Press the shutter now!”, and the moment my finger started pressing the shutter. This physiological time lag is probably highly personal and variable depending on the person’s state of alertness.

1 comment:

Duane said...

I have often thought that one main difference between an amateur photographer and a professional photographer is that the amateur takes thirty six shots of thirty six different things and is unhappy when only a few come out good, while a professional takes thirty six shots of the same thing and is very pleased when a few come out good.