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Lens adapters and focal length.

Discussion in 'Adapted Lenses' started by GShooter, May 20, 2012.

  1. GShooter

    GShooter Mu-43 Regular

    This may be an ignorant question, but does mounting a legacy lens using a lens adapter alter the focal length; in other words,does it act in the same way as using a macro extension tube by moving the lens further away from the sensor?
  2. Ned

    Ned Mu-43 Legend

    Jul 18, 2010
    Alberta, Canada
    No, the adapter keeps the original register distance which the lens was made for, simulating the original mount of the camera it came off of. So nothing changes.

    There have of course been cases where people will adapt lenses made for a shorter register to a longer register, such as adapting a rangefinder lens to an SLR. Doing this will turn that lens into a macro lens which may be incapable of shooting non-macro. We don't have this problem though with the short register of our mirrorless cameras. Just about any lens made can be adapted with its original register distance kept.
  3. An adapter doesn't act as an extension tube; it places the lens at the exact (or almost exact :wink:) same distance to the sensor/film plane as it would have been on the camera that the lens was originally designed for.
  4. AnttiV

    AnttiV Mu-43 Regular

    Apr 19, 2012
    This is relevant enough that I think I should post here rather than start a new thread...


    What's the difference between adapters of same mount-to-mount? For example, there are multiple M42-to-Micro43 mounts available, with price ranges of about $2 to $200. I can't for the life of me figure out how that $200 adapter can be THAT much better than the $2 adapter.

    (Most unbelievable case I've bumped into, was a M42-to-SigmaSA adapter. The one I bought was about $2.50 from China and I was told that it was "the worst adapter ever" and then pointed to a Japan-made "real, better, if more costly" adapter. That was ~$150. And I can't figure out what's the difference! The are both visually EXACTLY identical. Both are said to be made from solid brass, both allow focusing to infinity. I just CAN'T figure out why should I pay $150 for a piece of brass that I can get for $2.50. I can't.

    Is there ANYTHING that can be the difference between them? The other adapter could be 0-1mm thicker/thinner so it could alter the focal length.. but it wouldn't then focus to infinity, would it?

    ps. I know (I've seen) that there are extension+adapter type gadgets out there. A M42-to-SigmaSA adapter is just a small ring (the register distances are almost the same), but I've seen M42-to-Canon (Sigma and Canon have identical register distances) adapters that are 20-30mm long. So they essentially convert a normal M42 lens to a Macro Canon lens. I don't get the point really, because you can as well use a normal adapter and a $20 extension tube, but, well, just my 2c.
  5. Peng Kang Hill

    Peng Kang Hill New to Mu-43

    Aug 29, 2011
    Hi all,

    I hope I'm not off-topic but I found something strange when I used a Voigtlander 35/2.5 and adaptor to my E-P3.

    Although the lens specs indicate minimum focus distance of 0.7m, I'm getting about 1m.

    Anyone noticed this, too?

  6. Sawfish

    Sawfish Mu-43 Regular

    Nov 11, 2011
    I have a couple of the cheap adapters, but have never tried the expensive ones. The cheap adapters often need small modifications. One of mine had sharp edges on the flange, causing it to cut in the lens cap. Another had weak springs, causing a loose fit on the lens. It takes time to make these changes, but on the other hand, buying a 200$ adapter for a 50$ lens (one of my expensive ones) feels awkward.

  7. fin azvandi

    fin azvandi Mu-43 All-Pro

    Mar 12, 2011
    South Bend, IN
    I would hope that the more expensive adapters are manufactured to stricter tolerances, but I'm not going to spend the extra $$ to find out. I just received a cheap Hexanon AR-m4/3 adapter and it focuses rather farther past infinity than my other (cheap) one. I may try to shim it up, but I'll probably just leave it on the macro lens and not worry about it.
  8. Brianetta

    Brianetta Mu-43 Veteran

    Sep 5, 2010
    North East England
    Brian Ronald
    This is caused when an inexpensive lens adapter maker, which might not be able to stick to the sort of tolerances required, errs on the side of caution when making the adapter. It's better to lose a little at the close end and be able to focus past infinity, than to gain a little close focus and lose infinity completely. So, the lens is mounted slightly too close, and all the distance markings on the lens will be out by a fixed amount.
  9. DeeJayK

    DeeJayK Mu-43 Hall of Famer

    Feb 8, 2011
    Pacific Northwest, USA
    As others have already pointed out, the adapter is designed to put the lens at the same "focal flange distance" or "register" as it would be in the camera the lens was designed for. The reason that :43: (and mirrorless designs in general) are great for using adapted lenses is that the native :43: register is just 19.25mm, which is quite short. For comparison here is a pretty comprehensive list of registers for nearly any camera mount. You'll notice that different adapters have different depths (e.g. Leica M adapters are fairly thin while Pentacon 6 adapters are quite protuberant); the reason for this difference is the registers of the different mounts.

    Keep in mind that the Field of View of a legacy lens mounted on a :43: body is going to differ from the FOV on the original system because of the 2x "crop factor" of the :43: sensor as compared to 35mm film. Here's the best explanation I've read (from Amin) on how the smaller sensor will impact your results.
  10. DeeJayK

    DeeJayK Mu-43 Hall of Famer

    Feb 8, 2011
    Pacific Northwest, USA
    I think fin is right on the money here. I guess if I had a bunch of pricey Leica lenses I would be much more likely to spring for the expensive Novoflex or Voigtlander adapter. But since my legacy lenses consist of yard sale finds, I'll take my chances with the cheap ones.

    I have heard stories of cheap adapters that attached themselves to lenses and would not let go, so if you are going to go that route, I would suggest not mounting your prized f/1.2 that your grandfather bequeathed to you until you've tried it out with a lens to which you are not as attached.
  11. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    FWIW, even with fancy adapters, I've not found the focusing scales on adapted lenses to be particularly accurate.

  12. Laurentiu Cristofor

    Laurentiu Cristofor Mu-43 Veteran

    Mar 9, 2012
    Based on the brand and no-brand adapters that I used, the main difference is build quality.

    Each adapter has two parts - body and lens one.

    On body side, the problems I have seen is that the adapter doesn't fit tightly onto the camera mount, so it allows some movement. (Funnily, the Pentax M42 adapter does exactly this, but it is perceived as an advantage in that case, because you can remove the adapter easily - it sits entirely inside the K mount; this is an exception though - in general you want a tight fit).

    On the lens side, screwmount adapters are usually nice - everyone knows how to do threading. OTOH, for bayonet, the expensive adapters seem to have a better construction with tabs to keep pressure on the lens mount - the inexpensive ones usually just rely on a tight fit and the lens locking mechanism. Such extra details will make production more expensive for brand adapters.

    Overall, the brand adapters may also be more precise and likely to allow infinity focus. I have two generic adapters from different sellers - M42 and LTM - and I cannot focus to infinity with many lenses when used wide open. I am still not sure whether this is a lens issue (perhaps old lenses were never meant to accurately focus at infinity wide open) or an adapter issue, but I suspect the adapters.

    None of the issues is big enough to say that is justifies a $200 cost over a $2 or $20 one. But it can explain the price difference. :) 
  13. Peng Kang Hill

    Peng Kang Hill New to Mu-43

    Aug 29, 2011
    Hey thanks a million Brianetta. Looks like I'm paying the price for buying a cheap adaptor (sorry, no pun intended). :rofl:

    Think I'll live with it for now because it's not a major concern for me.

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