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Thread: Deciding on a 4x5 for digital conversion project

  1. #11

    Join Date
    Dec 2012
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    12

    Re: Deciding on a 4x5 for digital conversion project

    Quote Originally Posted by BTMarcais View Post
    I think you're missing something here. Just because an 80mm is a standard lens on the 645 doesn't mean it won't still behave like an 80mm lens on a full-frame 35mm sized DSLR. It'll be a short tele, not a standard lens.
    Dividing by .66 isn't really going to do anything for you.
    -Brian
    Am I? An 80mm MF lens would give a FOV roughly equal to a 120mm in a standard DSLR lens on full frame. A 35mm MF lens would get me a FOV equal to about 53mm on the sensor. The difference would be that it will likely have a closer minimum focusing distance which would have additional benefits as I see it.

    For my uses the biggest issues I see are the shadowing that can be caused by the DSLR flange during extreme movements and possibly chromatic aberration using wide angle lenses. I don't need any adapters from China as I am a capable machinist with my own shop. In fact, that is part of the reason I want to do this project. I haven't made anything interesting in the shop in a while.

    Bob

  2. #12

    Re: Deciding on a 4x5 for digital conversion project

    Make me one.

    How much would you charge to machine a Rollei 600X lens mount to lens board adapter?

  3. #13

    Join Date
    Nov 2008
    Posts
    182

    Re: Deciding on a 4x5 for digital conversion project

    It's been done many times before, so you should have no trouble doing it. The mirror box on the dslr is a big limiting factor for tilts. A spherical panorama head will be much more efficient than shifts. The sensors may not tolerate off axis light very well either. One of the EVIL cameras with a telecentric lens would be the best starting point

  4. #14

    Re: Deciding on a 4x5 for digital conversion project

    " An 80mm MF lens would give a FOV roughly equal to a 120mm in a standard DSLR lens on full frame"

    I'm sure you have this off.

    An 80mm MF is going to be 80mm on the DSLR. But the 80mm on the DSLR is going to be like a 120mm on MF(or close enough).

  5. #15

    Join Date
    Dec 2012
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    12

    Re: Deciding on a 4x5 for digital conversion project

    Quote Originally Posted by RichardSperry View Post
    " An 80mm MF lens would give a FOV roughly equal to a 120mm in a standard DSLR lens on full frame"

    I'm sure you have this off.

    An 80mm MF is going to be 80mm on the DSLR. But the 80mm on the DSLR is going to be like a 120mm on MF(or close enough).
    Ok, I am no expert on optical theory but what is there besides projected image circle and flange focal length? Light enters the lens and light exits the lens. The longer the focal length, the smaller the FOV entering the lens and the larger the projected image circle. A wide angle lens has a tight image circle focused at the film plane whereas the film/sensor only covers a small portion of the image circle on a long lens. Because I am planning to use 645 lenses the flange focal length is basically standardized so that will not be an issue. The size difference between a 35mm sensor and a 645 film plane is easily determined making it an easy calculation to determine FOV coverage at the sensor. So, what "behavior" variable am I missing? I have done a lot of research and I have seen this question asked before and people throw out the same answer every time with no explanation; something along the lines of "It will still be an 80mm lens". That answer speaks to nothing.

    Bob

  6. #16

    Join Date
    Jul 2012
    Location
    Michigan
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    101

    Re: Deciding on a 4x5 for digital conversion project

    https://www.box.com/s/y08pcw82m4csmoikmyu2
    https://www.box.com/s/sd2b1gbhysmzfmtdqvs0
    I went a bit in the other direction, machined up a lens board for my 4 by 5 Speed Graphic to adapt the Pentax 67 Bayonet mount.
    The P67 lens covers the 6 by 9 roll film back, but not much, if any, extra for tilt and rise.
    The register of the P67 is about 85 mm. The front standard is locked on the rear rail at infinity then the lens is focussed normally using its scale.
    I am still learning about using this and starting to get some nice sharp images, so far I have a P67 1:4.5 75mm lens which is a versatile one on the 6 by 9.

    I have no real plans for a digital back. Is there a digital back that will fit directly on the 45 Speed Graphic on the register of the ground glass?

  7. #17

    Join Date
    Sep 1998
    Location
    Loganville , GA
    Posts
    14,409

    Re: Deciding on a 4x5 for digital conversion project

    "I have no real plans for a digital back. Is there a digital back that will fit directly on the 45 Speed Graphic on the register of the ground glass?"

    Linhof makes an adapter to convert any Graflock 45 camera to accept any Hasselblad H compatible digital back. No focus plane adjustment needed to the 45 camera.

  8. #18

    Join Date
    Jun 2010
    Location
    Alameda, CA
    Posts
    31

    Re: Deciding on a 4x5 for digital conversion project

    Bob-- (ranger bob)
    Maybe we're just not understanding the way you're stating the focal length thing? It looks like you have at least part of this right, flange length and image circle. I think where we're all confused is what you think the angle of view is going to be on your DSLR. Not sure whether it's a real confusion as to what the effect will be, or just issues with terminology.
    An 80mm lens is ALWAYS an 80mm lens, and won't act as anything different. Because we're talking different formats though, the angle of view will be different for an 80mm on a mamiya 645 than it will be on a canon 5dmkII DSLR. a 80mm lens would be a standard focal length on the mamiya, but would have a narrower angle of view on the canon. Even if it was the same exact lens. Using the Mamiya lenses give you a bigger image circle than the 35mm lenses, but the angle of view will be the same as if it was a lens for 35mm in the same focal length.
    80mm for 4x5: very wide angle
    80mm for 6x9: moderate wide angle
    80mm for 6x6/545: standard
    80mm for 35mm (or 5dmkII): short portrait length
    Hopefully that makes us all less confused?
    -Brian

  9. #19

    Join Date
    Mar 2006
    Location
    Pittsfield, MA
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    784

    Re: Deciding on a 4x5 for digital conversion project

    RB/RZ lenses have a much longer FFL, around 105mm, putting them into the "easy to make work on a view camera" category.

  10. #20

    Re: Deciding on a 4x5 for digital conversion project

    [QUOTE=Ranger Bob;970485]From what I've read, tethered in live view works great for this creating a quick, efficient workflow.

    Bob[/

    Nothing could be further from the truth, live view is a utter pain and frankly pointless, as you might have little experience using a Sinar p2 with a medium format lens you may not be aware of the technical difficulties using such a combination particularly with a 35mm camera adaptor, but I suppose as somebody who is working every day with capture one using hasselblads, sinars and very occasionally canon 5d mk11's any well meaning advice offered should be countered by hearsay and well intentioned mis information .

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