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View Full Version : I want a 6x7 adapter!



Michael Carter
10-12-2007, 12:08 PM
Any of you engineering guys playing with this?

I was looking at my Mamiya gear the other day; haven't shot film in ages, was thinking of eBaying it all... but man, even the original RB bodies & lenses seem like great adapter raw materials...

The RB and RB ProS are just boxes with a bellows, mirror, and (giant) focusing screen. (The differences between the pro and pro s deal primarily with film advance and dark-slide safety - they're the same as far as making an adapter would go).

Why would this excite film makers? Well, first off, test all of your 35mm lenses. You'll find they're generally sharpest at around f5.6, with most being remarkably soft wide open... but with adapter light-loss, lots of you guys must be struggling just to shoot wide open, much less stopping down. Most of the big Mamiya lenses have a sharper operating range.

Next would be the GIANT imaging circle... 6 centimeters for medium format - that's 60mm on the ground glass; talk about reducing grain size (by, literally, almost 50%). And that's with 6x6 gear; 6x7 (like the mamiyas) would give you a 70mm x 60mm imaging area.

Cons? Weight & size issues... sticking a mamiya or hasselblad box on your camera would take a rail system. Also, the lenses have shutters built-in, adding more weight. AND the lenses arent as fast; there's few 2.8's in the 6x6/6x7 MF world.

On the plus side (again) there's a lot of russian hassy knock-offs out there as well...

Just looking at that big mirror box, and thinking "wow, you could get a motor in there..."

Easom Aerospace
10-13-2007, 07:42 PM
Michael,

Yes.... I have experimented with both 6x7 and 6x4.5 (Mamiya only) and found the 645 to be the better choice. The 6x7 makes a wonderful giant image, but mostly unusable without being reduced. Just the reducer lens out the back of the 6x7 lens could break the bank. It would make a great static adapter if you're just filming SD stuff. The lack of lens focusing ring was a negative for me. With the bellows focusing, a rack focus also gains a slight zoom in/out effect during the focus as the whole lens is moved back and forth. I was testing 90mm and 150 soft focus in the f3.8 to f4.0 range. The thread with my 645 test is here.

http://www.dvxuser.com/V6/showthread.php?t=110922

Page 5 has the most useful post about light and Medium format lens use. It also has a few diagrams I made up to help explain the difference and in many cases, the benefit of larger lenses.

Great question and I hope this helps some.

Cory Easom