Have I made a mistake with this camera?

Discussion in 'Large Format Cameras and Accessories' started by leeturner, Apr 15, 2006.

  1. leeturner

    leeturner Subscriber

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    I've decided to have a go at large format as I need movements for a project I've started working on. I've invested in a Sinar Norma (unbelievably cheap) for studio type work and certain architectural work. I also picked up an old MPP Microtechnical for carrying around. However the MPP is a MKIII and looking on the MPP users club it states that the MKIII doesn't have an international back. There is a section on registers http://www.mppusers.freeuk.com/registers.htm
    that states that lenses may have to be stopped down when using modern holders. Does anyone know what the register is and how it can be adjusted? If it's not possible to use modern film holders with this camera it will have to go on the auction site.
     
  2. Steve Hamley

    Steve Hamley Member

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    Lee,

    The international back just means it can take graflok accessories. It doesn't necessarily have anything to do with the film plane spacing. I'd think a Mark III would probably do fine with modern holders, have you tried it out? Is the film sharp?

    You could always send it to S.K. Grimes or Ken Ruth for a checkup.

    Steve
     
  3. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    You should be fine with standard filmholders in the MPP. As Steve says, you just won't be able to use things like rollfilm holders requiring a Graflok/international style back. The film plane register of 4x5" filmholders has been standardized for a very long time.
     
  4. Helen B

    Helen B Member

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    I've had an S92 for over thirty years (from Fenham's in Newcastle) and never noticed a problem with MPP holders, Riteways and a Polaroid 545. However, 0.187" is only 0.05 mm away from 4.8 mm and if that was a measurement to the film plane, who knows how accurate it was? The standard depth from the face of a film holder to the septum is 5.0 mm, with an allowance of 0.2 mm for the film thickness. Is there any way that you can measure the comparative depths of the GG and the septum of a film holder to see if there is other than 0.2 mm difference? Couldn't you shoot a test wide open with a distant object?

    Best,
    Helen
     
  5. leeturner

    leeturner Subscriber

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    Thanks for the replies. I'm still waiting for the camera to arrive so I'll try it with a standard fidelity holder and see what happens. I wouldn't be shooting anywhere near wide open with this camera and won't be needing a roll film back so that doesn't seem like a problem. The only thing I'm worried about is being able to use a standard holder without focus problems.
     
  6. Richard Kelham

    Richard Kelham Member

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    Helen's S92 is virtually the same as the later Mk.VII and Mk.VIII cameras in terms of film plane register, whereas the older cameras such as Mk.III had register at 5.08mm (instead of 4.8mm).

    As suggested, do a test wide open and see if there is a problem (not one caused by the lens of course) and if so fit a 0.28mm shim (approx 10 thou). Or buy as many old MPP dark slides as you can find. Oh and a type 500 Polaroid back as that is the only one that will fit.

    I'm very fond of my Mk.VII MPP – a very rugged camera, though the Mk>VIII had more movements and was as good as a Technika (and half the price).

    Happy shooting...
     
  7. leeturner

    leeturner Subscriber

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    Thanks Richard. One thing I need to know is where is the register measured from (in a roundabout way, what is the register)? I've seen quite a few MPP film holders for sale but some are marked as plate holders and from what little I've learnt these need a sheet film adaptor. Is there any particular model to look for? Still for what I paid for it (£60, the price of a boring night out at the local) it's worth giving it a go.
     
  8. Richard Kelham

    Richard Kelham Member

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    I was afraid you might ask that! :-(

    I presume the register is the distance from the focussing screen to the back of the camera – ie the plane that the DDS sits on, under the spring back.

    As has been intimated, stopping down to say f22 should be enough to cope with a 10 thou variation with most lenses. And as you say, for 60 quid you can't complain!


    Richard
     
  9. MichaelBriggs

    MichaelBriggs Member

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    On a filmholder the depth is the distance from the outside of the filmholder, that rests agaist the camera, to the septum against which the film rests. On the ground glass back, you want to measure the equivalent distance to the ground surface of the ground glass. Normally the ground glass will be aboout 0.007 inch closer to allow for the thickness of the film.

    The standard depth for 4x5 filmholders is 5.0 mm = 0.197 inches, which implies the ground glass should have a register of 0.190 inches = 4.83 mm. The ANSI filmholder standard specifies a tolerance of 0.007 inch. The table http://www.mppusers.freeuk.com/registers.htm gives the register for the MKIII as 0.200 inch = 5.08 mm (avoiding metric, they were...). So, right off, if a MKIII is exactly on its target register, its just past the ANSI standard tolerance: 0.010 versus 0.007 inches

    The ANSI spec is reasonable. The equation for depth of focus is +/- C N, where C is the diameter of the circle of confusion and N is the f-number. A standard value for C for 4x5 is 0.1 mm; supposing f11 as the fastest taking aperture, gives +/- 1.1 mm = 0.04 in. This is larger than both the ANSI tolerance and the likely register difference between the MKIII and the standard.

    Also, it is possible that Lee's camera (which he doesn't even have yet) has been modified or upgraded in the many years since it was made -- hopefully for the better, possibly for the worse. I suggest a careful photographic test of the focusing accuracy, or a measurement of the register with a depth micrometer, or both, rather than relying too much on the table of the original specs.

    I haven't seen a MKIII, but most cameras have the position stops in front of the ground glass, so adding shims will move the ground glass away from the lens, increasing the register, which is the wrong direction.
     
  10. leeturner

    leeturner Subscriber

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    Thanks Michael for the detailed explanation, the circle of confusion now rests in my head :smile:. It looks as though it all comes down to testing as both Michael and the MPP site mention that general wear and tear or modifications can make a difference. According to the register page the register can be adjusted so it's looks like it's going to be a worthwhile £8 to join the user club. Upon joining there's apparently another site with a lot more info and discussion on the cameras though I doubt there's not much that can't be answered on APUG, as the above replies prove.
     
  11. Curt

    Curt Subscriber

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    If the film holder and the gg measure the same .187 or 5mm then what would be the cause of a fuzzy image? ...And the image is sharp on the ground glass when viewing... ???Motion as a possible cause??? either the camera or the subject/test.