Questions about Mamiya Press 65mm lens

[BarryS]

I just received a Mamiya Press 65mm lens and if any of you have experience with this lens--I have a couple of questions. Does the aperture open completely when the lens is wide open? On my lens, when the aperture is opened to f/6.3, the iris blades don't open to the full round diameter of the lens elements--they stop short and form a pentagon--is this normal?

The helical is also very stiff. I imagine the grease has dried out and needs to be replaced. Has anyone ever disassembled the 65mm (or other) helical, cleaned, re-lubed, and successfully reassembled it? Thanks.

Barry​

 

[sevo]

It does not open to the maximum. This is quite common in leaf shuttered lenses, as the aperture is part of the separately supplied shutter assembly whose diameter will not always match the desired maximum aperture, so that some difference may have to be compensated for by adjusting the aperture end stop.

Mamiya Press lenses are quite easy to take apart, compared to a SLR lens - but you'd better have (or loan or purchase) a ground glass as you will have to readjust its focus after the fact. Within the last year or so there was a pretty enlightening discussion on Mamiya Press lens adjustment (which inevitably included disassembly) here on the forum, but I can't find it any more. Maybe someone else saved a link or has a smarter method to search the forum?

 

[BarryS]

Sevo--thanks for your help. I have many modern large format lenses in shutter and I believe the apertures all open up completely--none are limited at the wide end by the iris. In some older designs like simple meniscus lenses, wide angle rectilinears, and sometimes Petzvals--there's a limiting stop because of degraded performance "wide open".

Just to confirm--you have the 65mm? I may have seen the thread you were referring to and there's some discussion of repairing the shutter, but I haven't seen any posting where a helical was disassembled. Thanks.

 

[sevo]

Just to confirm--you have the 65mm? I may have seen the thread you were referring to and there's some discussion of repairing the shutter, but I haven't seen any posting where a helical was disassembled. Thanks.

I have the 65mm, yes. By the way, mine is a little stiff as well - given its very short throw that might be intentional, I've seen (or rather felt) the same on other short throw lenses.

IIRC it was no thread on shutter repair but a thread on helical adjustment of the 100mm, but as most press lenses (the exceptions being the last 100mm revision and the 50mm) have a fundamentally similar helical, that should apply to the 65mm as well.

 

[besk]

There is a mechanical stop to keep it from opening wider. And it was put there for a reason.
One fellow reported on one of the forums that he had removed that stop. (I have two of these 65's and the focus is a little stiff on both.)

 

[BarryS]

Thanks Sevo and besk--it sounds like my 65mm is typical. I may leave the helical alone for now and see how it works in the field. There seem to be divergent opinions on the quality of the 65mm, but I've seen some very crisp images done with this lens.

 

[ulysses.o]

mine does that and here are some photos taken with it

The Stickr Bandit by ulysses.O, on Flickr

Nick's Super Market Sweep by ulysses.O, on Flickr

Smurf Condos by ulysses.O, on Flickr

There Once Was A Building Named Alice by ulysses.O, on Flickr

 

[kuzano]

Test for coverage vs 50 and 75mm Press

Test for coverage vs 50 and 75mm Press

There is an image comparison between the M-Press 65, 50 and 75mm lens for 6X12 coverage (or not) on this page:

http://www.bigcamera.com/articles/images/4X5X6X12TEST.gif

In addition, there is a bit of information on the 65 in the same web site:

http://www.bigcamera.com

No, the aperture does not open anywhere near all the way.

And, re the stiff helical, usually nothing that sitting in front of the tv (for something to do) and working the helical for a couple of hours does not limber up.

One of the three 65's I have had resisted that exercise, and I resorted to a limited "ronsonol flush". A very light application of lighter fluid around the front edge of the focus ring. Be very careful not to "flood" the lens aperture and shutter blades. Just enough fluid to reach down into the helical threads.

It's way too easy to get too much fluid in the lens/shutter with the "ronsonol flush" straight from the bottle. I usually soak a clean cotton rag and just squeeze a bit of the lighter fluid down into the edge of the focus ring so it runs down into the stiffened grease.

Many decry this method and then go ahead and use Naptha (virtually same) or other fluid that dries without residue. The backup is that the lens can always be taken apart and cleaned/lube, but I have often found the "flush" used moderately to be quite enough to loosen up the grease a bit on a fifty year old lens. Lightly though.

Three 65's and tons of other Press lenses and leaf shutter style lenses including old folders and large format.