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Lens Mount/Sensor Size Question

Discussion in 'Open Discussion' started by Replytoken, Jul 8, 2016.

  1. Replytoken

    Replytoken Mu-43 Hall of Famer

    May 7, 2012
    Puget Sound
    Ken
    I'm not one to normally post about "what if" camera designs, but I did get a bug in my bonnet after a recent shoot involving my E-M1 and a FX DSLR. Suppose that a camera company wanted to produce both mirrorless and DSLR bodies that utilized the same lens line-up without any adapters. Assuming that the mirrorless body and lenses were m4/3rd's, roughly what would be the size of the DSLR body's sensor?

    --Ken
     
  2. Carbonman

    Carbonman Mu-43 All-Pro

    Jul 10, 2014
    Vancouver BC
    Graham
    The only way you could cram a mirror between a m43 lens and sensor would be to have it use some sort of diffractive technology for the mirror because there's no way to fit a 45 degree mirror in that space. It would require a permanent focal reducer to build enough space for a conventional DSLR mirror/pentaprism setup.
     
  3. Replytoken

    Replytoken Mu-43 Hall of Famer

    May 7, 2012
    Puget Sound
    Ken
    I realize that there needs to be room for a conventional mirror (which I should have stared more clearly as part of my assumptions), so that would mean a smaller sensor, but what I do not know is how much smaller. Let me come at it from another angle. Could I get the CAF/tracking AF performance of a high quality DSLR in a body that could use my existing lens set? I realize that the sensor would need to be smaller, but how much? Smaller than a 1" sensor?

    --Ken
     
  4. Nathanael

    Nathanael Mu-43 Veteran

    390
    Oct 12, 2015
    Well in the change from 43 to m43 they halved the flange from 40mm to 20mm. So I'd guess a mirror and sensor setup for 20mm flange is about half the size of the m43 sensor. So smaller than 1".

    ^^ this is all speculation
     
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  5. dwig

    dwig Mu-43 Top Veteran

    622
    Jun 26, 2010
    Key West FL
    The flange distance (register) is not the actual limiting factor. What matters in this OPs question is m43's spec for the minimum spacing between the sensor and the rear element and all other lens barrel components. I haven't seen the numbers, but I suspect that the distance that components can extend into the body is greater for m43 than it is for the older 4/3 mount.

    My guess is that a moving mirror SLR using m43 lenses would have to have a ridiculously small sensor given the little space left for the mirror. You could get a slightly larger sensor if you use either some elaborate mirror design (horizontally spilt mirror with the lower portion moving down and the upper portion moving up, a single mirror swinging down and sliding forward like the earliest Bronica, ...) or use a fixed pellicle mirror (Canon Pellix, ...) or a fixed beamsplitter.

    Sigma has shown a new mirrorless body that uses their DSLR lenses without adapters. To accomplish this they've used the DSLR mount with its large register distance. The resulting body has some of the advantages possible in a mirrorless body but isn't significantly smaller than it sister DSLRs.
     
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  6. TNcasual

    TNcasual Mu-43 All-Pro

    Dec 2, 2014
    Knoxville, TN
    Forgive me for going off topic, but the Nikon 1 system supposedly has very fast AF. It is also capable of using Nikon f-mount lenses.

    Also, there are AF adapters for using DSLR lenses on Sony E(F)-Mount cameras. As well as the autofocus adapters available for mft.
     
  7. Replytoken

    Replytoken Mu-43 Hall of Famer

    May 7, 2012
    Puget Sound
    Ken
    Thank you for the above replies. I was not certain how much of a reduction in size would be necessary, and we still do not know exactly, but the collective thought seems to lead me to believe that this was not as feasible as I would have speculated. The prompts for this query were recent shoots where I brought both my E-M1 and my D610. Each has great strengths and weaknesses, and while I do not mind carrying two different types of bodies, I do object to carrying that much glass (and the size of the D610 when travelling). I suspect that mirrorless improvements in EVF lag and CAF/tracking will keep closing the gap, as was called out in the post above about the Nikon 1, but I fantasized for a moment about having two bodies (mirrorless & DSLR) that could share one set of compact lenses and allow me some of the advantages from each system. Now back to my regularly scheduled reality.

    Thanks,

    --Ken