How manufacturing tolerances can screw you!
Back in 1987 I
bought my first 35mm SLR - an EOS 650, with the 35-70 f/3.5-4.5
and 70-210 f/4 zoom lenses. I shopped around the various vendors in the
back of Popular Photography and eventually brought that info to a local
camera store and basically said I didn't expect to meet the price, but
did value a local contact should there be any issues and expect if he
wanted the business to see what he could do about discounting off list
The owner, a man looking like he was in his 60s, came down
somewhat - not to where mail order was but enough that I felt it was a
win-win, so made the purchase. About 3 months later I exhausted my
first $20 battery - a 2CR5 and quickly popped in another. Within a
week, that one was drained.
After spending $100 in batteries, my spidee sense told
me something was seriously wrong with my equipment. So I split one
battery apart, removed the cells, and attached small wires to the inside.
Bringing those wires out of the camera and soldering wires to a couple
of nails and a rubber band, I was able to make a brand new 2CR5 battery
as an external battery where I could now insert a current meter to see
just how much juice the camera was taking.
Taking lots of measurements and cutting to the chase ...
When I left
the 70-210mm lens mounted to the camera, the current consumption of the camera / lens
combination was about 1000x higher when powered off than it was when the
35-70mm lens was attached or if no lens was attached! It was as if the
70-210mm lens was preventing the camera from turning fully off, though
there was no indication in the camera itself that it wasn't turned off. So if I left the
70-210 on the camera powered off and in the camera bag, in a day or two my battery was
the entire setup to the camera store. Described what was happening and
asked if I could first demonstrate then use some of his demo stock to
isolate the problem. I didn't know if I had a problem with the camera or
with the lens. He agreed. All setup, demonstrated, then I took a
couple of different 70-210 lenses and when connected to my camera all
went down to a couple of micro-amp draw instead of milliamp draws when powered off
just like the 35-70 did. Then I tried a couple of different EOS 650
bodies. When connected to my lens, none of those bodies with my lens
exhibited the problem.
The problem was only apparent with my lens and my camera
The owner wanted me to send it to Canon for warranty
work, and in the end he exchanged it in the store - which was why I
wanted a local face to buy from. I just couldn't imagine Canon setting
everything up the way I had to see the problem firsthand and thus be
able to diagnose / repair it.
Everything is built to a certain specification, and that
spec has an error margin on every measurement. This is true for
everything - the tiles on your floor, the wood 2x4s that are in the
walls of your house, the batteries that power your equipment, every
electrical component in everything electrical, etc. Those errors can
sometimes align themselves in opposite directions and have interesting
In my case, something about either the electrical
connections or the data timing between the lens and camera were likely
causing something in the camera to think it needed to keep applying
power to the lens, and thus my combination was eating batteries for
So that is my camera / tolerance story...