View Full Version : Electronic shutter timer

Lawrence Floyd, Jr.
18-May-2004, 11:14
Has anyone ever built or used electronic shutter timers to help with long exposure acuracy? I'm having a little trouble getting long exposures acurately using my wrist watch stop watch feature.

Bob Salomon
18-May-2004, 11:58
Just how accurate a long exposure are you after?

Ernest Purdum
18-May-2004, 12:03
Over the years there have been many. Process cameras sometimes had such devices. Ilex made a timer they called a "Speedcomputer" for use with their electric shutters. Melles Griot picked up the product line from Ilex and redesigned the timer. Unfortunately, there are interchangability problems regarding these. Also, the timers are harder to find than the shutters and the cable between timer and shutter is harder to find still and not easy to duplicate. Several people have made their own timers for these shutters or are working on them.

Electronic controlled shutters with times up to 32 seconds were made for awhile by Compur, Prontor and Copal. They were very expensive, apparently didn't sell well and soon left the market. If found today, there may be battery problems and I don't know of anyone willing to take a shot at repairing one. The problem is that the shutter people won't want anything to do with the electronics and electronic people don't want to touch the mechanism.

It isn't electronic, but Prontor makes, or has made, an auxiliary clockwoork timer which is used as a cable release. It is expensive, though.

The hard part of timing long exposures are those in the two to four second range. The problem is reaction time. Beyond that, a watch, or "calibrating" yourself to count accurately by practicing against anything that displays seconds can produce accuracy well equivalent to 1/3 stop.

Arne Croell
18-May-2004, 12:12
In the 1970's, Compur built their "Electronic" shutters (sizes 1,3,5), as well as Copal their "Electric" ones. Both went up to 32s in the normal one-stop increments (1-2-4-8-16-32s). Prontor built a "Magnetic" shutter that may have had the same feature. All of those show up on ebay occasionally, and the size 1 and 3 versions are compatible with modern shutters. The original batteries, at least for the Compur, are no longer available, but can be replaced with other versions. For the smaller size shutters (0, 1), there are also the recent Horseman ISS and the Rollei versions, which are controlled by a central command unit (the same was true for the huge Compur 5 electronic, btw). Bobs question is right: remember that for an exposure time of, say, 30 seconds, an error of 3s is practically negligible, even if 3s sounds a lot. An error of just 1/3rd of a stop is a factor of 1.26 (3rd root of 2) in time! For the above 30s example, +/- 1/3rd of a stop is between 24s and 38s, approximately. 1/6th of a stop is a factor of 1.12 (6th root of 2).

Lawrence Floyd, Jr.
18-May-2004, 13:47
Right. Beyond 4 or 5 seconds, no problem. 1 to about 4 seconds and my reaction time just isn't what I would like it to be.

18-May-2004, 15:38
The prontor timers look good.

When I worked only with my one barrel lens, I had to time from 1/2 to 4 or 5 seconds by watch. At 2 seconds I was right on the mark. Mostly.

I don't think it's really worth it, but logic would say that the easiest way would be to adapt an electric solenoid to a donor cable release. This could be used for remote activation, or, more to the point, timed operation. It should be something with q-u-i-c-k reaction time, in both directions. Then it could be hooked up to anything from a simple electronic timer to a handheld PC.

A simple setup could be had that does all this, supplies the power, and takes up the space of a smaller lightmeter.

If you need a hand with this, I'd be willing to help with the programming (if needed) and assembly.

Charlie Skelton
19-May-2004, 05:12
Re 2-4 second exposures. I find it best to avoid these by going down a stop and doubling the time + a bit for reciprocity.

Arne Croell
19-May-2004, 07:05
The 2s one is obviously the toughest, but again taking +/- 1/3rd of a stop variation means the actual time can be anything between 1.6 and 2.5 seconds. I think that is doable watching the second hand on a wristwatch (which is what I do). Try it with a stopwatch replacing the cable release/shutter when watching your wristwatch, or counting, if you prefer that (without looking at the stopwatch!). This should give you a good idea how close to 2s you get.