Does Mamiya 645 AF retain auto diaphragm with MF lenses?

[jon_porter2]

<p>Both the 645 AF instruction manual and all the forum posts I've seen are ambiguous on this point. They only state that manual focus M645 lenses must be stopped down to use TTL metering, which I don't care about. I'd like to pick up an AF body, but if there's no auto diaphragm feature with the older MF lenses the camera is of little use to me. Thanks for any enlightenment on this!</p>

[ron_dfaux]

<p>"Retain auto diaphragm" is a little ambiguous. If you expect the camera to automatically close/or open up the aperture based on your aperture setting on the camera, then, no, it does not do it.<br /> I use the 120mm MF macro lens on my Mamiya 645 AFII body. Since it is a manual lens, the aperture is set manually on the lens, and the camera can only control the shutter speed.<br /> The procedure to take the picture in this case is as follows:<br /> 1. Set your lens aperture to the widest setting to allow the most light for focusing (as you start stepping down the aperture, the viewfinder screen becomes progressively darker, which may present challenges in focusing).<br /> 2. Focus your shot. The camera's TTL will suggest the correct shutter speed when the lens is wide open.<br /> 3. Start stopping down the aperture on the lens to the desired setting for your shot. You will notice that the viewfinder becomes darker, and the camera's TTL will suggest the correct *slower* shutter speed. Depending on the camera mode, you may need to set the correct shutter speed (in Manual or Shutter modes) for proper exposure.<br /> 4. Take a picture.</p>

[jon_porter2]

<p>Thanks, but I'm not sure you understood me, Ron. I'm talking about setting the aperture on the lens, not on the camera. I don't care about any form of metering with the camera. So, for example, if I set f/8 on the M645 lens will it remain wide open until the instant of exposure, then reopen instantly once the shutter closes? From your description it sounds like it doesn't. </p>

[gregory_king1]

<p>Yes, as he said, there is no auto aperture. The AF cameras can neither operate the aperture on the MF lenses nor activate the shutter on the LS lenses. They can only tell an AF lens when to stop down.</p>

[jon_porter2]

<p>Got it. Thanks guys. So the 645 AF has a fully electronic handshake between camera and lens with no mechanical support. Technology marches on...</p>

[ondebanks]

<blockquote>

<p>So the 645 AF has a fully electronic handshake between camera and lens with no mechanical support.</p>

</blockquote>

<p>It also means that you could only use the AF lenses on a manual focus [MF] body (or on a DSLR with adapter) at full aperture, wide open. Most people would find that much too limiting.</p>

<p>There's also a mechanical impediment, at least with the 55-110 AF zoom that I have - the bayonet is the same on the AF lens, but the smooth flat part of the flange extends a little wider than it does on the MF lenses/cameras. So my AF zoom won't fit on my Zoerk M645-T2 adapter, nor on my M645 1000s bodies. You can see this size difference when you fit an MF lens to an AF body - the outer perimeter of the body flange is still visible with the MF lens attached. Of course, this has no effect on the mounting or operation of the MF lenses on the AF bodies. It's just the other way round that there's a problem.</p>

<p>This is one of the reasons why I have only that one AF lens, and use MF prime M645 lenses for everything else on my 645AFD body and my DSLRs.</p>

<p> </p>

[gregory_king1]

<p>Ray,</p>

<p>Yep, that flange difference keeps the AF lenses mounting to even the MF bodies.</p>

<p>The low cost of Mamiya m645 manual focus equipment is so low, I plan to keep mine after I unload my AF gear.</p>

[ondebanks]

<blockquote>

<p>The low cost of Mamiya m645 manual focus equipment is so low, I plan to keep mine after I unload my AF gear.</p>

</blockquote>

<p>Are you getting out of the 645AFD system, Gregory? That's a surprise. And your RZ too? What about your digital back that worked on the pair of them? </p>

[cristobal_rey]

<p>what about changing the focusing screen screen to the SF402...can i still use AF lenses normally or i need to change the screen every time???</p>

<p>thanks</p>

[ondebanks]

<blockquote>

<p>what about changing the focusing screen screen to the SF402...can i still use AF lenses normally or i need to change the screen every time???</p>

</blockquote>

<p>You can use the AF lenses with any focusing screen.</p>

<p>The AF sensors are in the floor of the mirror box, so the light hits them independently of the light diverted to the focusing screen.</p>

<p>The only contribution of the focusing screen to AF use is that some screens are engraved to show the small central areas of the scene that the three AF sensors are seeing. This is merely a visual assist for the photographer; once you are familiar with the location of these areas, you can mentally project them onto any screen.</p>