using 645 lens for 6x7 format

[ghost1001]

Hi All,

Anyone have experience using mamiya 645 lenses with a 6x7 back.

I plan to build a medium format camera with these components.

I am trying to figure out if the image circle will cover the 6x7 format.

Short of testing i do not expect a absolute answer, but would like to know if anyone has tried it.


Thanks
Kevin

[keithwms]

Consider the flange-to-film distance and whether this will allow you to focus at infinity. If you're making a bellows rig then no problem, but mounting a 645 lens on an rb, for example, you will have issues.

In terms of coverage, yes, it'll be tight but doable for some lenses at reasonably close focus, so for macro it's fine. However, apart from the issue of coverage, there may be no sharpness benefit.

If it were me I'd just grab some RB lenses while they're still there aplenty on the market... then you will have enough coverage for basic movements at close focus.

[ghost1001]

Hi Keith,

The reason for the 645 lens is that the body will be fixed...no bellows, and the 645 lens will focus the RB's will not. I plan to maintain the standard film plane distance for the 645 at 63.3mm.

I would like to shoot macro with tubes on the camera so that should cover the 6x7, but I would also like to shoot at infinity.

Worst case I will have a great 645 image in the midle of a 6x7 negative?

I quess I could use a 6x4.5 RB back.

I want the camera to be small and light so I think the 645 lens would be best.

My next will project use the RB lens with a bellows body, or a helical focusing lens mount.

Thanks
Kevin

[keithwms]

Kevin, you could get that 100-200 zoom, that one has helicoidal ability, if I remember correctly.

But I see your point about focusing.

Hey, I think you can get a helicoidal mount for LF lenses from fotoman... just another stray thought.

The main attraction of the 645 lenses is that they are *way* faster than the RB lenses. There is the 80-/1.9 for example. I am considering rigging that onto my horseman VH. On a speed graphic that'd be nice, then I'd have a shutter.

[Greg_E]

You could also look at the Mamiya 645 Super/Pro backs. They are pretty simple to mount to a camera body.



Sorry, it's the best scan I can get right now. Scanned at 150ppi with the ruler for size reference.

[ghost1001]

Cool,

Thanks...can you advance the film with the back off-camera?

If so how?

Thanks

[Greg_E]

The knob on the left side (attached to the gear) will advance the film to the nexxt frame and stop. Then you need to push the release pin (top left) in order to wind it again. If you really wanted to get fancy you could use a handle with a gear to wind the back. I assume that the Rb/RZ backs work in a similar way.

[ghost1001]

thanks for the explination.