Wrong batteries= Dark motion pictures?

[superadio]

Hi folks. After having many films too dark from my Canon 318 and 518. See example here: http://www.youtube.com/watch?v=wZG5s9nd1gY I have done some investigation regarding the 2 small batteries for the lightmeter. The batteries in my camera was not 1.35 V, but replacement batteries at 1.5 V. I got hold of some wein cell, who supply 1.35, and put them into camera. I than compared reading from lightmeter to F stop, and I could see the camera adjusted appreture 1 F stop lower (bigger opening) with the 1.35 V. If this could be what makes my films dark, could be important information to other filmmakers. Thanks for your attention.

[aj]

Indeed, many camera-exposure systems run fine with 1.5 instead of 1.35 volt. Other need exact 1.35 volt. Somebody in Norway is installing electronic circuits into cameras to draw and adapt 1.35 from the drive-batteries.

Better to check ahead of time of exposing real film.

[johnmeyer]

I had exactly your problem with my 1970 Nikon F fTN SLR. It used 1.35V mercury batteries (two of them) in the light meter. When mercury batteries went away in the late 1970s, I substituted 1.5V alkaline. For several years, all my exposures were dark. I suspected the exposure meter, but never suspected the batteries. My solution for the next decade was to lie to the exposure meter and set the ASA lower, so if I was shooting ASA 100 film, I'd set the ASA to 50. That worked pretty well, but I didn't think I got consistent results.

When the Wein cells became available, I read the literature about them, and that's when I became aware of the 1.35V vs. 1.5V issue.

I started using the Wein batteries, and my problems were over.

The Wein cells became available at about the same time as the Internet was taking off. One of the posts I found back then was from someone who had reversed engineered the Nikon exposure meter circuit. I am an EE by training, so this was incredibly useful. The primitive circuit in this 1970 design had absolutely no compensation for battery voltage: the higher the voltage, the further the exposure needle would travel. So, with a higher voltage, the needle went further to the right, and you had to increase the f-stop more to get it to center. Higher f-stop means darker picture.

So yes, at least with my old Nikon F camera, the voltage was definitely the culprit.

[threeinv]

Another option is the Gossen adapter kit (if your light meter takes 2 batteries):

http://www.bhphotovideo.com/c/product/8 ... r_for.html

- Derrick

[aj]

Or this:
http://www.fotografica.nl/batt-adapt-US.pdf

If your handy with electronics

[super8man]

Or this one:

http://home.pacbell.net/mnyberg/super8mm/super8_20.html