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Submitted in a kindly spirit: Interesting discussion on NEX Flange back challenges.

Discussion in 'Other Systems' started by WT21, Aug 7, 2011.

  1. WT21

    WT21 Mu-43 Hall of Famer

    Feb 19, 2010
    Boston
  2. drizek

    drizek Mu-43 Veteran

    492
    Aug 5, 2011
    What's the problem?

    Isn't the flange distance exactly the same as A-mount with an adapter? The images from an adapted lens should be the same on the NEX cameras as they are on the alpha cameras.

    I think their real mistake is not allowing for in-body IS in search of super slim bodies. So now they have made the body even smaller and the lenses either extremely large (kit, superzoom) or unstabilized (pancake).
     
  3. drizek

    drizek Mu-43 Veteran

    492
    Aug 5, 2011
    Interesting quote from NEX 7 rumor at SAR

    sonyalpharumors | Blog | (SR3) A NEX-7 one minute hands-on report...(Zeiss with leaf shutter?)
     
  4. WT21

    WT21 Mu-43 Hall of Famer

    Feb 19, 2010
    Boston
    The lenses tested are M mount, not A mount lenses.
     
  5. Mellow

    Mellow Mu-43 All-Pro

    Aug 27, 2010
    Florida or Idaho
    Tom
    Very, very interesting . . this has always been my suspicion. The extra 2mm (18 vs. 20, if I recall) DOES appear to make it difficult to get sharp corners, especially at wide angle where the light is entering at a very sharp angle.

    If they can fix this with micro-lenses, great, but I wonder if m43 hasn't found the sweet spot in terms of minimum flange distance with minimal image degradation due to angle of incidence.
     
  6. WT21

    WT21 Mu-43 Hall of Famer

    Feb 19, 2010
    Boston
    I think there are two issues -- getting closer AND going wider (because of the larger sensor). I guess also digital is more susceptible to this issue than film was, which might explain why Canon hasn't released a compact mirrorless, like I dearly want them to (that, and not wanting to kill off their DSLR business, but it seems the engineering is more than just simple. Could you imaging the angle of incidence in trying to cover a 2X larger sensor than the m43 sensor, with a short flange back, if the NEX is having issues?

    Like you, I am thinking m43 might be the "sweet spot" but they've got to improve that sensor a bit, to keep up. At least the lenses are finally starting to arrive :) (said the person with an open PL25 order since May).

    The discussions on sonyalpharumors, and then the link through there to a Fred Miranda discussion were interesting reads, and the jury still seems out.

    p.s. -- this bit does some nice explaining http://www.fredmiranda.com/forum/topic/1030741/1#9793822. It is interesting to learn that Leica does in-camera software correction! I didn't know that.
     
  7. Hikari

    Hikari Mu-43 All-Pro

    Nov 26, 2010
    The flange distance of the Nex camera does not make any difference--the M mount adapter has to hold the lens at the M mount flange distance. This would be true for any camera. The slight difference in sensor size between APS-C and m4/3 is not really significant especially when you consider the two images will effectively be enlarged at different magnifications. The only issue would be the micro lenses used on the sensors. But where could you get those specs?

    All digital camera have some type of in-camera lens correction if the lens can be read. The question is what happens when there is no communication between the body and lens.
     
    • Like Like x 1
  8. Mellow

    Mellow Mu-43 All-Pro

    Aug 27, 2010
    Florida or Idaho
    Tom
    But the flange distance does matter for native NEX lenses, which nearly all suck at wide angle, especially in the corners where the light enters at the sharpest angle. Isn't this true?

    And I don't understand your argument that the sensor size doesn't matter. Isn't it straight physics that the shorter the lens-sensor distance and larger the sensor the more the light has to be bent?
     
  9. Hikari

    Hikari Mu-43 All-Pro

    Nov 26, 2010
    For a simple lens, but not a telecentric design (but this is a relative problem too, see below). The flange distance is a physical distance which does not necessarily apply to optical distances--how can a telephoto lens be physically shorter than its focal length, for example. (BTW, maybe the Sony lenses suck rather than being a sensor problem.)

    Simple geometry. For any given angle of view, the incident angle will be the same regardless of sensor size. The larger the sensor, the larger the permissible circle of confusion (the limit to what appears sharp), so larger sensors don't require as good optics as smaller ones. This is a relative problem of scale not a problem that can be defined in a single absolute frame.
     
  10. squeegee

    squeegee Mu-43 Veteran

    403
    Jan 26, 2010
    If i recall proplerly, for native 43 & m43; the spec says light leaving the lens is suppose to be perpendicular to the sensor. If that's true then. The distance for m43 systems is irrelevent and micro correction lenses would not be useful (for native lenses). I think thats why they say 43 is suppose to be good in the corners.

    (but on an unrelated note, what would be interesting would be a large lens that widens the incoming image, say to 4x the size, then incidenting that on a 4x larger sensor...)
     
  11. JJJPhoto

    JJJPhoto Mu-43 Veteran

    252
    Jul 8, 2011
    Cincinnati, OH
    Jerry Jackson Jr
    OK, maybe I don't understand something, but shouldn't the flange back distance on the NEX only matter for native NEX lenses? Any adapted lens uses an adapter and thus the distance to the image sensor remains the same as what it is on whatever mount the lens was designed for. This might also explain why legacy lenses seem so much sharper than Sony's own E-mount lenses.
     
  12. Amin Sabet

    Amin Sabet Administrator

    Apr 10, 2009
    Boston, MA (USA)
    Yes, you've got it right.

    Sent from my HTC Thunderbolt using Mu-43 App
     
    • Like Like x 1
  13. Hikari

    Hikari Mu-43 All-Pro

    Nov 26, 2010
    The flange back is a mechanical distance for mounting a lens. It has nothing to do with the quality of the optics.
     
  14. WT21

    WT21 Mu-43 Hall of Famer

    Feb 19, 2010
    Boston
    Yes, it is impacting new lens design, and may be a reason Sony has been slow in getting out quality lenses. It seems that a) Sony didn't expect NEX to be a hit with more serious hobbyists, and b) it impacts making both small AND well corrected lenses.

    It seems that with m-mount lenses, which are also designed for a short flange back distance on M bodies, the Leica bodies are employing both special sensor corrections and software corrections. So, if you are mounting M Mount lenses, and the NEX body doesn't have the sensor corrections (and it has no way of knowing the lens on the camera), then it does impact the quality of that legacy glass. So, this is not really an issue of NEX using a short flange-back distance, but it does speak to the fallacy that NEX + M lenses = just a crop of an M9 FOV. It's actually more complicated than that (though still yielding pretty good results, it's not up to par as on an M9 -- there is color shifting, softer corners, and also not as sharp, though that is more down to the AA filter, from what I've read).

    A great discussion on this at Fred Miranda is here: Sony NEX-C3 first impressions - FM Forums
     
  15. drizek

    drizek Mu-43 Veteran

    492
    Aug 5, 2011
    Panasonic has an official M adapter, right? Do they do any sort of correction with Leica lenses?
     
  16. WT21

    WT21 Mu-43 Hall of Famer

    Feb 19, 2010
    Boston
    No, so the issues should be the same when adapting M lenses (different issues with Native lenses). Same with Oly, too.


    (which is also why I said "So, this is not really an issue of NEX using a short flange-back distance")
     
  17. drizek

    drizek Mu-43 Veteran

    492
    Aug 5, 2011
    So now the real question is, did Oly and panasonic screw up by making the flange distance on m43 too long instead of just correcting for it in the sensor like Sony and Leica?
     
  18. Hikari

    Hikari Mu-43 All-Pro

    Nov 26, 2010
    Flange distance has nothing to do with image quality. Period.

    Olympus and Panasonic do correct for THEIR lenses. Most manufacturers do not profile lenses made by others, especially lenses not designed for their cameras.

    No one "screwed up."
     
  19. WT21

    WT21 Mu-43 Hall of Famer

    Feb 19, 2010
    Boston
    Can you explain more, since short flange back distance certainly seems to impact color shifting on digital sensors, as even Leica has to correct for it. But it seems an acceptable tradeoff for compactness.
     
  20. squeegee

    squeegee Mu-43 Veteran

    403
    Jan 26, 2010
    Are you *sure* about this? The way i read it, although i may be wrong, is that the nex system uses lenses that send light to the sensor at an angle, similar to most nikon/canon/alpha dslr's. This means even with native nex lenses there is a problem. I.e. they require micro lens correction on the sensor itself, i.e. Effcetively what they need/want is a curved sensor. My understanding with 43 / m43 native optics is that this is corrected in the lenses themselves so by the time light hits the sensor it is already straightened (on native lenses).

    if that is true, then yes the flange distance matters as a longer distance will create angles closer to 90 degrees and therefore match the sensor surface closer, and it would mean yes, sony screwed up in either not correcting the light angle in lens or picking too small of a flange distance. This might also explain why m43 lens' look not much shorter than nex lenses, m43 needs more length to do correction while nex doesn't correct at all.