I also have had inaccurate readings from a IV f. I bought it at a camera show yesterday and, like the fool I am, did not check the readings against my camera. When I got it home, I realized that it was 4 or more stops underexposed! Indeed, there was a rattling sound coming from the diffuser chamber.
I removed the battery, then unscrewed the two screws on the rear of the diffuser chamber. Several small colored discs and washer-like spacers came out. That was the rattle! I thought I had bought a broken meter (well, I had, but I thought I had one beyond repair).
In desperation, I got out my magnifying glass and tried to repair the thing.
The discs were a clear one, a grey one, and a green one. There were three “washers” or spacers. In the chamber, there is a piece of tin on two pegs. I lifted this off and under it, there’s a piece of oval plastic with the light sensor going through it. The face of the light sensor should sit behind the discs in the round hole that you can see from the front of the unit if you remove the diffuser dome. This oval piece should sit under two plastic lips to keep it in place. Mine had come loose from the lips, allowing the sensor to come free as well as the discs.
Using a pair of tweezers, I gently replaced the discs with the clear one going in first, then the grey one, then the green one. Then I put in the spacers. In retrospect, I should have layered the discs and spacers, I think. Anyway, I then pushed the sensor back into the oval plastic bit, then pushed the oval plastic bit down and twisted it so that it rested under the plastic lips. This then kept the sensor, discs and spacers nested in their hole. I replaced the back of the diffuser chamber.
I have only tested the meter in ambient mode, but it is now very close to the metering on my Fuji X100s. The grey card metered on the Minolta at 400 ISO, 1/60 at f2.0. The Fuji X100s measured the grey card at 400 ISO at 1/52 at f2.0.
Much better than the 4 full stops when I started out, and within the tolerances of the calibration knob on the back of the IV f.
Has anyone else had this experience upon opening one of these?
Last edited by LinusK; 03-10-2014 at 01:55 PM. Click to view previous post history.
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