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iangreenhalgh1
Joined: 18 Mar 2011
Posts: 15679
Expire: 2014-01-07
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 Posted: Wed Feb 06, 2013 6:39 pm Post subject: Putting a Mamiya 645 2.8/45 in a shutter |
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iangreenhalgh1 wrote:
Hi folks
This is probably a bit of a mad idea, but I am a bit mad 
I bought a box of lenses with issues a while back for next to nothing and in there was an abused Mamiya 2.8/45. The barrel was a mess so I removed the front and rear cells and cleaned the glass. There's a lot of scratches on the front but otherwise, the glass is okay.
I measured the size of the cells and the front is 27mm unthreaded, the rear is 28mm threaded, as close as I can tell with a ruler.
Seems to me, with a bit of epoxy and shimming, I should be able to cram these cells into a shutter.
Thing I don't know, and have failed to work out from measuring the barrel, is the correct cell spacing.
How critical is the cell spacing?
What shutters are there that will probably suitable for stuffing these cells into? Has to be cheap, so maybe I can rob something from an old folder?
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luisalegria
Joined: 07 Mar 2008
Posts: 6602
Location: San Francisco, USA
Expire: 2018-01-18
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| Posted: Wed Feb 06, 2013 8:07 pm Post subject: |
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luisalegria wrote:
Cell spacing is very important. Changing that will change the corrections for CA, etc., and I expect the potential sharpness of the system.
Some people play with cell spacing to get special effects. You can try it yourself with any lens in shutter by partially unscrewing the cells.
Just how accurate you have to be with a given lens is iffy and I guess it depends on what you want to achieve. I expect wide angle types like your Mamiya would be pretty sensitive.
27-28mm are fairly large as these things go. The typical shutters that took 10.5cm lenses on roll film folders are smaller. The next larger size for 13.5cm/4.5 lenses is more like what you want and may be very close (just under 30mm on a Compur if I am measuring right).
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I like Pentax DSLR's, Exaktas, M42 bodies of all kinds, strange and cheap Japanese lenses, and am dabbling in medium format/Speed Graphic work. |
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iangreenhalgh1
Joined: 18 Mar 2011
Posts: 15679
Expire: 2014-01-07
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| Posted: Thu Feb 07, 2013 6:40 am Post subject: |
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iangreenhalgh1 wrote:
Cheers Luis. You are right, it won't fit a folder shutter, I tried that as I have quite a few folders.
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ZoneV
Joined: 09 Nov 2009
Posts: 1632
Location: Germany
Expire: 2011-12-02
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| Posted: Thu Feb 07, 2013 9:01 am Post subject: |
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ZoneV wrote:
| luisalegria wrote: |
Cell spacing is very important. Changing that will change the corrections for CA, etc., and I expect the potential sharpness of the system.
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+1
You see at some lenses washers to adjust cell spacing for production tolerances.
I have a DIY project to build automatic iris in old manual lenses. There I have to get the same cell spacing as well.
The Canon EF aperture cells have much mechnics and the engine which interfere with the lens sometimes and this prevents further work with a combination of lens and iris :/
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iangreenhalgh1
Joined: 18 Mar 2011
Posts: 15679
Expire: 2014-01-07
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| Posted: Thu Feb 07, 2013 2:52 pm Post subject: |
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iangreenhalgh1 wrote:
Cheers. I'll just have to experiment and hope I can get a sharp result. CA isn't a problem as I'll only be shooting bw with it.
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danfromm
Joined: 04 Sep 2011
Posts: 595
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| Posted: Thu Feb 07, 2013 4:09 pm Post subject: |
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danfromm wrote:
| iangreenhalgh1 wrote: |
| Cheers. I'll just have to experiment and hope I can get a sharp result. CA isn't a problem as I'll only be shooting bw with it. |
Ian, about cell spacing. Don't focus on that, instead make sure that the lens in shutter is the same length as it was in barrel. This will get the desired spacing.
About CA, it will reduce sharpness in b/w. Where did you get the idea that CA doesn't matter for b/w?
Also, I'm very surprised that the rear cell is threaded and the front cell isn't. Are you sure that you disassembled the thing correctly?
The thread's title is "Putting a Mamiya 645 2.8/45 in a shutter." Do you really have an M645 wide angle lens? |
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ludoo
Joined: 18 Sep 2009
Posts: 1397
Location: Milan, Italy
Expire: 2011-12-05
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| Posted: Thu Feb 07, 2013 4:20 pm Post subject: |
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ludoo wrote:
Ian use a vernier caliper instead of a ruler, it's precise to 1/20 of a mm. 
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luisalegria
Joined: 07 Mar 2008
Posts: 6602
Location: San Francisco, USA
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| Posted: Thu Feb 07, 2013 4:38 pm Post subject: |
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luisalegria wrote:
Keeping the total length constant (or a measure from fixed points on the front and rear cells) is an easy way to verify cell spacing.
The only measurement this doesn't control for is the iris location, and I don't think that is so significant.
A Mamiya 645 45mm lens in its intended format would be like a 30mm(more or less) on 35mm and mounting one on a 4.5x6 folder in a hyperfocal fixed focus way would be an interesting project.
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iangreenhalgh1
Joined: 18 Mar 2011
Posts: 15679
Expire: 2014-01-07
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| Posted: Thu Feb 07, 2013 10:36 pm Post subject: |
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iangreenhalgh1 wrote:
This is the lens I had:
I was surprised the front cell wasn't threaded. The barrel was a mess so I threw it away, so that will make measuring the length of the lens a bit difficult. 
I know CA will affect sharpness in BW, what I meant was, I can live with a little bit of CA in BW whereas in colour, I hate it.
Luis, that was my idea - to put this thing on a modified 6x6 folder, I suspect the image circle stopped down will be enough to cover 6x6.
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