Please explain "A" and "M" settings on Mamiya manual focus lenses

[Graham_Martin]

I have a Mamiya 645AFD, and I have a 500mm manual focus lens as part of the small "herd". I asked this question on another forum and it was explained to me that the M setting is for depth of field review, and the A setting is for actually taking the picture. However, I seem to have misunderstood something because it is still unclear to me. I have even looked at a couple of Mamiya Instruction manuals and something is blinding to me to what I am sure is a simple answer.

For example, if I want to shoot at f/8 what exactly should I do when setting up the shot?

Thanks

 

[flatulent1]

On the M645 cameras they refer to Automatic and Manual aperture control. On A the camera controls the aperture, on M you do.

 

[MattKing]

Not quite right, Fred. The only auto-exposure functions on Mamiya 645 cameras are aperture preferred.

The designations either don't make sense, or no longer make sense.

The "A" is used for open aperture metering on the manual focus cameras. The "M" is used for stop-down metering on the manual focus cameras, and for depth of field preview. I have never used an AFD body, but my understanding is that on the Automatic Focus bodies, you can only use metering in stop-down mode, so I would assume that you need to set the manual focus lenses to "M" on those bodies in order to meter with them.

Matt

 

[flatulent1]

I see I'm going to have to play with mine again...

 

[Ian Grant]

Matt, the A & M do mean Automatic and Manual, so Fred was partially correct.

But the A setting means the camera automatically stops down the aperture to the pre-set aperture after the shutter release is pressed prior to the shutter opening, and it returns to full aperture afterwards.

The M setting is used on bellows etc where there's no mechanical linkage.

Ian

 

[MattKing]

Matt, the A & M do mean Automatic and Manual, so Fred was partially correct.

But the A setting means the camera automatically stops down the aperture to the pre-set aperture after the shutter release is pressed prior to the shutter opening, and it returns to full aperture afterwards.

The M setting is used on bellows etc where there's no mechanical linkage.

Ian

Like back in the day, when open aperture metering was the newest thing .

I had forgotten about using the lenses with bellows - it certainly makes sense that "M" for manual would still be used for that purpose.

Matt

 

[suzyj]

The M setting is also useful on bodies without a DoF preview button, like the M645. It's a tad fiddly, but you can stop the lens down to check depth of field by flicking it across to M, then take the shot.