Mamiya 645 Pro AE Prism Questions

I just re-discovered SLR photography again with a Mamiya 645 Pro TL that I purchased from KEH with a few lenses and the AE prism. But I'm a bit confused as to the operation of the prism. I shot the camera today and found myself simply using my Pentax digital spot meter for every shot.

First of all, the display in the viewfinder doesn't stay up long enough to view. It flickers when the shutter is held halfway down. Secondly, spot meter offers no advantage to me if I cannot see + and - on a scale in the viewfinder (I'm used to Nikon displays) and the meter in matrix metering seems to want to under-expose compared to my other cameras. And lastly and most importantly, once mirror lock up is activated the meter reading is lost, unless of course you either hold the shutter half way down in AEL mode until you take the photo, or use the meter to get the reading, then dial in the shutter speed. Anyone have the solution to this last problem?

Overall I'm just rather disappointed with the AE prism and am thinking I will just stick with my hand held spot meter for readings with this camera. So I'm thinking of exchanging for an un-metered prism.

Thoughts? Advice?

In-camera meters are certainly limited. I'd stick with the spot, or an incident for more speed (not much slower than using an in-camera meter). Or if you have time, use both – the incident for finding your normal exposure, and the spot for measuring the brightness range of the composition and making tweaks to your normal exposure and development.

Brian:

Do you have the manual?

http://www.butkus.org/chinon/mamiya/mamiya_645_ae_prism_finder/mamiya_645_ae_prism.htm

Assuming your metering prism is similar or the same as mine, (mine is a type introduced with M645Super), if you set your shutter speed to A or AEL, it turns your body into an aperture priority system. Set your aperture and the shutter speed is set for you. It flickers between two numbers when the metered speed is in between the two.

If you have it in A position, the metering it uses is the value when shutter is released. In AEL position, by half way pressing the shutter button, you can lock the reading.

If you have it in any other position, it shows the shutter speed it thinks you should use, given the aperture setting. You will have to take your eye off the view finder, and set the shutter speed manually.

You meter can be set to a SPOT only mode, Average only mode, or automatically switch between the two. I have no idea what logic it uses to switch between the two.

To me, this is quite useful. I keep mine in AEL mode unless I have a reason to do anything else.

MattKing said:

Brian:

Do you have the manual?

http://www.butkus.org/chinon/mamiya/mamiya_645_ae_prism_finder/mamiya_645_ae_prism.htm

Click to expand...

Thanks Matt. No I don't have the manual. I understand pretty much everything about the camera, just not the prism. I will print this out.

tkamiya said:

Assuming your metering prism is similar or the same as mine, (mine is a type introduced with M645Super), if you set your shutter speed to A or AEL, it turns your body into an aperture priority system. Set your aperture and the shutter speed is set for you. It flickers between two numbers when the metered speed is in between the two.

If you have it in A position, the metering it uses is the value when shutter is released. In AEL position, by half way pressing the shutter button, you can lock the reading.

If you have it in any other position, it shows the shutter speed it thinks you should use, given the aperture setting. You will have to take your eye off the view finder, and set the shutter speed manually.

You meter can be set to a SPOT only mode, Average only mode, or automatically switch between the two. I have no idea what logic it uses to switch between the two.

To me, this is quite useful. I keep mine in AEL mode unless I have a reason to do anything else.

Click to expand...

Understood, but how about holding a reading when locking the mirror up?

brian steinberger said:

Understood, but how about holding a reading when locking the mirror up?

Click to expand...

Just read the manual quickly thanks to Matt. Seems that the only way to use MLU and the AE prism is to hold the shutter halfway while locking the mirror up just as I thought. Other than that there is no way.

For mirror lock up work I have the camera on a tripod and use the meter in manual.

EDIT: It is fairly easy to flip the meter up and down to check for exposure changes.

EDIT2: By the way, this link to a list of Mamiya manuals on Mike Butkus' site is one I use over and over and ....

http://www.butkus.org/chinon/mamiya/mamiya_lenses_accessories/mamiya_lenses_accessories.htm

Brian,

I don't use MLU as I hand hold mine most of the time. If I had a need to use MLU, I'd use a tripod and in that case, I won't be using AE. It really is a limitation of SLR that we can't meter while the mirror is up....

I decided to send the AE prism back and got a non-metered prism. I'm much happier with it, I'll use my spot meter for metering.