Adding the B function to a MF leaf lens, Or…?

My story…..
I (sometimes) shoot Star Trail Photos, 5hr exposures onto film. I’ve been using a Mamiya Press with fair results, mostly chasing light leak issues, but it works good overall. My main issue is I don’t use the set up often enough (mostly during new moon nights only, when the weather is clear, when my schedule allows) so a roll of 120 film sits in the camera for long periods of time. I want to change over to 4 x 5 sheet film so I can shoot single photos and send them off for processing individually and quickly. (I know I should just shoot more images!)

The lens… LF lenses are $$$ and I need to shoot at 5.6 or so f-stop where most LF lens don’t go (very well at least). I’ve been thinking about morphing a MF lens onto a LF camera (I had high hopes for the Wanderlust but can’t hold out forever so will build my own P&S 4 x 5). MF lenses are much less expensive on the auction block plus they are fast, usually 2.8 but they lack a shutter obviously. So I need a shutter with the “B” Bulb function built into the lens or added on externally. I’ve never held a leaf lens so not even sure how they function let alone performing surgery on one! I thought about a Copal #3 shutter which has about 53mm opening but not sure if that is large enough to mate to a MF lens (w/special machined mounting plate…$$$!). I even looked at the Packard shutters as an option, mounted inside the camera behind the lens board.

I haven’t picked out a lens other than seeing Mamiya 645’s plentiful and less than $200. And yes I know I won‘t get full coverage onto 4 x 5 film, I don’t need it, I just thought a MF lens for cost and sheet film for convenience would be a good marriage for this special purpose camera.
Thanks for your feedback.

I suppose it depends what your budget is, but it seems to me you should reconsider getting a 'proper' 4x5 camera. Unless you actually *want* to do a DIY project, then good luck to you.

eBay can offer 4x5 cameras with lens for < $400 USD. I can't comment on the lens quality at f/5.6, but you've got a lot of film area on 4x5 vs. 6x4.5 to make up shortfall in image quality. Seems a shame to me to go to the trouble of using 4x5 just to put a little image in the middle of the film, but that's just me.

An interesting project though, if you do go ahead with it, and I'd be interested to see your star trail photos too.

I bought a Graflex Optar for a 4x5 camera from KEH for $40. It was an "UG" but it is beautiful.

Aren't lenses for the Mamiya Press system in leaf shutters?

Since you're willing to use lenses that don't cover the format on 4x5, why not use one of your lenses for Mamiya Press on your DIY 4x5 box camera? There are other medium format cameras that use lenses in shutter. Do some research.

So why do you need a shutter for a five hour exposure? Just get an older barrel lens or a newer lens on a sinar mount and use the lens cap.

A 4x5 Speed Graphic or Burke & James press camera should do you fine. And finding one with a 127-150 mm lens won't be hard or expensive. All in all, seems that using something like a Mamiya MF lens is going to take a lot of trouble to hack it to do what a few thousand press camera lenses do by design.

By the way, if you are having light leak issues on 5 hour exposures, just wrap the camera in a black clothe or inside a dark plastic bag? Here's an example:
http://www.sfmoma.org/explore/collection/artwork/27689#

Medium format lenses won't cover 4X5. I've tried a 105mm f4.5 Kodak triplet from a 6X9 and it is woefully short on covering power, corners completly dark. It would be ok if you like round images I guess.

Have you considered cutting a sheet of 4x5 to size (or a sheet of 2x3) and loading it into your Mamiya Press back in the dark?
Just position it into the film gate and close it up. If the sheet is too lose you can shim it with a piece of backing paper. If the back has a setting for 220, that might work better.

A sheet back would make things easier, but this would get you going with what you already have.
If you're determined to go the DIY cam direction, your press cam already has a leaf shutter. But you can get a serviceable Graflex with a lens for the sort of money you'd spend on adapting otherwise incompatible stuff (100 USD +or-).

As for a "B" setting, or whether to have a shutter or not, you don't really need one, just a lens cap will do for what you're looking to do.

Not sure if it is still available, but for the OP's reference, here's a B&J press camera with two lenses for $175 in the classifieds-
(there was a url link here which no longer exists)

Many cameras of this type floating around out there.

Thanks everyone for your input. It does make sense to just use the lenses I have for the Mamiya Press. I do still want to use 4x5 film, I checked into 2 1/2 x 3 1/2 film and only found one source for processing but I'd have to cut my own film, not something I really want to do. I'll let you know how the project turns out.
Dave