View Full Version : Horseman optical exposure computer

17-Jun-2008, 16:40
I had bought this exposure meter for 6x9 including 4x5 adapter, but helas, I don't have batteries. It wants PX-26 and PX-640 which couldn't be found anywhere in this planet now.

Would it be possible to modify this exposure meter or to use any alternative batteries? It's a shame, the meter is in very good condition.

Brian Vuillemenot
17-Jun-2008, 16:46
I have a Horseman metering back for my 4X5 that I got used from the 'bay. It came with a 5.6 volt mercury battery, which was dead, that aparently hasn't been produced for many years. I went to a store called Batteries Plus, which is a chain over much of the US, and they custom made me a battery composed of four 1.5 volt cells attached together. They chose the cells so that they were the right diameter to fit in the battery compartment of the meter- make sure you bring that to the store with you. The battery works perfectly, and is still running after about 5 years of use.

17-Jun-2008, 16:50
Thanks, Brian.

Do you remember the type number of those 1.5V cells? Was it OK with 6V instead of 5.6V?


17-Jun-2008, 18:23
I use various means to get 1.3v in my collection of meters from schottky diodes to Zinc-air batteries. However, for my Horseman meter, I exclusively use EI (exposure index) instead of ISO, so 1.5v batteries work fine for me in that one.

So, with the 1.5v batteries in the Horseman, I just shoot a Zone I frame and pick the EI that gives me 0.1 log above film base.

For B&W work, the changes in linearity with 1.5v & 6v batteries in this meter are too small to justify chucking these fine Horseman meters in the trash.

For battery A, I use a Duracell S28px 6v battery with a piece of plastic tubing around the battery so it doesn't wobble in the compartment.

For battery B, I use an Exell A640 http://www.exellbattery.com/detail.asp?PID=A640PX

Here is a link to the way I do it: http://www.photobattery.com/horseman.html
Here is a link to another way to do it: http://photo.net/bboard/q-and-a-fetch-msg?msg_id=0018jJ

17-Jun-2008, 19:53
Thanks! It's great helpful info!