Any suggestion about a precise time control in long exposures ? I use a sports chronometer, but I know that some people use mechanical self-timers; could somebody recomend me the best ones? Electronic self-timers for LF? I have only copal shutters. Thanks.

-- jose angel (acquatek@teleline.es), June 19, 1999

Answers

Hello Jose, My question to you would be: Do you really need such precise control of long time exposures? Keep in mind that for a twenty minute exposure you would have to overexpose by almost 7 minutes to overexpose even by 1/3 of a stop. A few seconds (or even minutes) is usually not all that critical. When I make long exposures (5 minutes or more) I usually lock the aperture open and use a lens cap as my "shutter" and time the exposure with a small pocket-size kitchen timer that counts down to zero and then sounds an alarm. (Your chronometer should be more than up to the task.) After the alarm sounds, I can run over to my camera (I'm often setting up another shot or scouting out another location) and end the exposure before overexposing too much. For shorter exposures I just stand around near the camera and wait for the alarm to ring. The "T" setting or "B" with a locking cable release will also work. For exposures of a few seconds I sometimes set the shutter at 1 sec and pop it off the required number of times. Interupting the exposure in this manner is especially helpful when the wind is moving things around a lot and the still periods are relatively short. Alternately, I just watch the sweep second hand on my watch. When I forget to wear my watch or bring the timer I just count seconds in my head. I'm a musician and tempo is trained into me, but with a little practice anyone can come within 10% or so when counting even 10 min exposures. This is well within tolerance. Hope this helps, :^D)

-- Doremus Scudder (ScudderLandreth@compuserve.com), June 19, 1999.

A studio I worked for used common quartz stop watches available at sporting goods stores to time their long exposures for furniture sets. They were shooting 8 X 10 chromes (among other things) and really didn't seem to be worried about the chronometer, as much as the person exposing the film.

-- Sean yates (yatescats@yahoo.com), June 19, 1999.

I use an inexpensive kitchen timer. I do prefer to use the count- down timer rather than the count-up timer (like a stop watch). I can react faster to the audio alarm from a count down timer. Precise timing becomes fairly important with shorter time exposures (like in the 2 second range).

-- Larry Huppert (Larry.Huppert@mail.com), June 20, 1999.

At a camera fair, I came acrosss an old mechanical timer. I didn't buy it.

I don't like exposures between 1 and 5 seconds because it doesn't take much error on my part to make a difference. I like to 'rehearse' the exposure, with the dark slide in place, so I can make the appropriate allowance for the travel in the cable release.

One of these days, I want to build an electric shutter release, so I can also trigger by radio, cut IR beam, or whatever, and a side- effect will be accurate long exposures. Doubtless someone has already done this.

-- Alan Gibson (Alan.Gibson@technologist.com), June 20, 1999.

Thank you all for your answers. The conclusion I read is that the best and cheapest system is the kitchen count-down timer (I never thought on it). The most critical times for me are two, four or eight seconds, and I can see that I use a similar system like some of you, the "precision finger system". I'm glad to read your contibutions to this forum.

-- jose angel (acquatek@teleline.es), June 20, 1999.