Canon 7 meter -- how does it work?

[john_van_v]

I just got a 7 for the 135mm framelines. I will supply a photo of it w/ its matching lens. (Dang, a heavy combo!)

Only problem is that the meter seems off, but I want to confirm. When I put the speed to 125th, it only shows f0.9 to about f4, which just cannot be! I don't know if there is a high-range/low-range issue, if the gearing is off, or if there is something I just don't get.

Other than that, the meter seems lively, which actually surprised me know it is selenium, despite what the seller said!

Thanks in advance, John

 

[xayraa33]

The best luck I had with working on board selenium cell lightmeters was on the Kiev 4

 

[John Shriver]

The meter is dirt simple. The selenium photocell is in parallel with the meter movement. The high/low switch (little notched knob on the back) presumably controls how much of the selenium cell is active. There may also be a parallel or series resistor for calibration.

The selenium cell is prone to losing output for a given light level with age.

The dial that rotates when you change the shutter speed or ASA has to be correctly "timed". Look at a known correctly assembled camera, look at the combination of shutter speed, ASA, and dial position. Your should be the same.

 

[Sonnar Brian]

There is a high/low setting, and it is color-coded. The switch has a red and black dot, and the F-Stop scale is also color coded.

It is not "too hard" to calibrate if is off. The shutter dial comes off with three set screws, see the gears underneath, align to a proper setting, and reinstall the dial.