Mamiya 645 Pro with AE Prism Issue

Hey all,

Am coming into the Mamiya universe from my Bronica RF645 after a sad story of the winder slowly breaking down on me and finding out no one seems to repair that camera anymore.

Loved the meter on the Bronica, and have equipped my 645 Pro with an AE Prism Finder. Right now I have that dialed in to Auto A-S and 0 for the exposure compensation. I'm noticing an issue that might be either due to my camera body, a faulty prism, or my own fault for not configuring all the settings properly.

Right now, I have the ISO set correctly, the lens seated correctly with the pin hooked in to the aperture ring, the A / M Lever set to A, the shutter set to A, and no M-lock. What I'm seeing through the prism are settings that I'd expect to see if I was shooting in manual mode — I see the "selected" shutter speed of 1/1000 lit up steady, and then the metered exposure blinking (usually 30 or 60 with the lighting I had). I'm confident I've selected all the correct settings such that this should be in AE mode and I shouldn't be seeing a "selected" shutter speed lit up since I'm on A, but I can't seem to make that 1/1000 light go away. Have cleaned the contact, switched back and forth on the A-M lever, reseated the lens, and reseated the prism.

Am I missing something obvious, or should I be worried about a specific part possibly being faulty? When I have the shutter selected to any value, the correct light shows up in the prism, but A seems to read as 1000 every time. Can't figure out what I'm doing wrong!

Welcome to Photrio.
I'm not sure you are doing anything wrong, but I would caution that these finders and cameras are very demanding on batteries, and if the battery is near to exhaustion, the displays sometimes behave strangely.
A fresh, silver oxide battery is highly recommended.
Also, it is to be remembered that there are electrical contacts in the battery compartment and on the film back, which also need to be kept clean.
Finally, I have one lens that has an aperture selected prong that doesn't always engage automatically with the corresponding pin on the meter (in my case, the version N that came out with the Super). I'd suggest checking that as well.

garamonds said:

What I'm seeing through the prism are settings that I'd expect to see if I was shooting in manual mode — I see the "selected" shutter speed of 1/1000 lit up steady, and then the metered exposure blinking (usually 30 or 60 with the lighting I had). I'm confident I've selected all the correct settings such that this should be in AE mode and I shouldn't be seeing a "selected" shutter speed lit up since I'm on A, but I can't seem to make that 1/1000 light go away. Have cleaned the contact, switched back and forth on the A-M lever, reseated the lens, and reseated the prism.

Click to expand...

As I recall (and as evidenced by reading the M645 Pro metering prism user manual) only the shutter speed(s) -- for intermediate values -- should illuminate, and since the shutter speed is set to 'A' the 1/1000 should not also be illuminated...I suspect a malfunction. I would try the metering prism on a different body, if one can be found.
When you put shutter on specific speeds with meter in M and shift speeds, do you see the correct 'selected speed' displayed in the prism?

do you still have the dark slide in?
also try using a setting on the AE head that is not A-S. I never used that.

Here's a photo of what I'm seeing in A mode, for future reference:

MattKing said:

Welcome to Photrio.
I'm not sure you are doing anything wrong, but I would caution that these finders and cameras are very demanding on batteries, and if the battery is near to exhaustion, the displays sometimes behave strangely.
A fresh, silver oxide battery is highly recommended.
Also, it is to be remembered that there are electrical contacts in the battery compartment and on the film back, which also need to be kept clean.
Finally, I have one lens that has an aperture selected prong that doesn't always engage automatically with the corresponding pin on the meter (in my case, the version N that came out with the Super). I'd suggest checking that as well.

Click to expand...

Thanks! This is a fresh battery and I cleaned all the contacts on the back, finder, grip, and body. As for the prong, changing the aperture moves the pin with it so it looks to be engaged cleanly.

wiltw said:

As I recall (and as evidenced by reading the M645 Pro metering prism user manual) only the shutter speed(s) -- for intermediate values -- should illuminate, and since the shutter speed is set to 'A' the 1/1000 should not also be illuminated...I suspect a malfunction. I would try the metering prism on a different body, if one can be found.
When you put shutter on specific speeds with meter in M and shift speeds, do you see the correct 'selected speed' displayed in the prism?

Click to expand...

No other bodies around to try this one out on unfortunately. Good call on trying it out in M mode! That's proved that it's a faulty finder, as some speeds never light up, some don't correspond correctly in the prism to the selected one on the wheel, and it seems to jump around as I scroll through (finder will show 60 lit, then 500 lit). I'll be asking for a refund on the finder and using an iPhone light meter app I suppose until I buy a replacement. Thanks a ton!