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Wide Angle Converter on Oly 12mm f2

Discussion in 'Native Lenses' started by tradesmith45, Sep 29, 2013.

  1. tradesmith45

    tradesmith45 Mu-43 All-Pro

    Dec 13, 2012
    Oregon
    Hey anyone out there tried using one of the wide angle converters on the M.Z 12?

    Need a fast UWA.
     
  2. KBeezie

    KBeezie Mu-43 Top Veteran

    697
    Sep 15, 2012
    Grand Rapids, Mi
    Karl Blessing
    Are you looking at a specific auxiliary lens? Cuz I'm just thinking wouldn't you utterly destroy the lens quality throwing that in front?

    Also bear in mind, just like filters (CPL etc), wide angle converters and such also reduce the effective amount of light reaching the sensor, sometimes as much as 2-3 stops, so it wouldn't actually give you any benefits of having a "Fast UWA". (think of it the same way teleconverter do).

    For clarification, say you find a cheapish WA convertor around 80-120$, it may not actually increase it to UWA capable without distorting the hell out of the edges, and would turn the Oly 12mm f/2.0 to roughly the amount of light a f/4.0 or f/5.6 lens would give, ergo putting you back to square one while also ruining the image quality.
     
  3. dougjgreen

    dougjgreen Mu-43 All-Pro

    Jun 5, 2013
    San Diego
    Doug Green
    Actually, they don't. Wide converters do NOT reduce the effective aperture, and if they are designed to do so, like the Metabones wide converters, they can actually increase the effective apertures. They actually work the reverse of the way teleconverters do, not the same way teleconverters do. But alas it IS true that the quality is likely to be substantially degraded unless the converter was actually optimally designed for the particular 12mm Zuiko lens.
     
  4. KBeezie

    KBeezie Mu-43 Top Veteran

    697
    Sep 15, 2012
    Grand Rapids, Mi
    Karl Blessing

    I'm a little confused on how more glass (ie: more material) can add more light. Would any of those converters effectively turn an f/2.0 lens into f/1.4 effective? Though I do know a teleconvertor would do much more so because its focusing down the focal length of course.

    But yea either way I can't think of any converters off the top of my head that are :

    1) Going to retain the same quality (or very close to) as the 12/2.0
    and
    2) One made specifically for it, seeing as most are designed to go on normal-ish lens to take the wide image area and place it down the normal focal length .
     
  5. dougjgreen

    dougjgreen Mu-43 All-Pro

    Jun 5, 2013
    San Diego
    Doug Green

    None of the existing converters which could be adapted to the 12mm lens actually do make it wider in aperture - they simply wouldn't reduce the aperture as you claimed that they would. But the Metabones converters do provide an existence proof that you COULD make a wide converter that actually made the 12mm f2 into an 8 or 9mm f1.4 - but it would be expensive, and it would need to fit between the lens and the mount. The Metabones converters do exactly the same thing for the current 35mm-designed lenses that they work with. Again, at this point, it's a return on investment issue, not an optical feasibility issue.
     
  6. KBeezie

    KBeezie Mu-43 Top Veteran

    697
    Sep 15, 2012
    Grand Rapids, Mi
    Karl Blessing

    See this is what's confusing me. Light couldn't be made brighter especially behind the lens.

    This is how I'm visualizing what you're saying.

    Imagine if you will light is grains of sand, the f/2.0 aperture for the sake of argument is a hole 2mm wide with the sand being poured down it.

    Now place a hole behind that one that's 4mm wide, twice as big, but the sand keeps flowing thru the 2mm hole and isn't going any faster. Flip the holes where the 4mm is in front and the 2mm is behind it... but it's still not going any faster thru the holes.

    Maybe I'm not a physicist or an expert, but seems like "adding" glass will always reduce the amount of light reaching the lens, in some cases may be negligible, in others more drastic, but in either case it's always less than without the add-ons.

    So unless you can show me how it would be the opposite of what I'm saying, I'm not going to be able to grasps your claim that a WA convertor will actually increase the effective light gathering of a f/2.0 lens down to f/1.4 by adding optical elements to the glass.
     
  7. dougjgreen

    dougjgreen Mu-43 All-Pro

    Jun 5, 2013
    San Diego
    Doug Green
    As I said, the Metabones wide converters already do EXACTLY what I said could be done, with existing 35mm optics. They are an existence proof of the concept. They alter the focal length of the lens, while fully utilizing the existing physical aperture. So, effectively, they take a lens with an x mm focal length, and a y mm aperture, and convert it to a 0.7x mm focal length with the same physical y mm aperture. Which basically is 1 f-atop faster than the original lens. I suggest you familiarize yourself with the Metabones converters before claiming that what they do can't be done. As I said, they are an existence proof. They act exactly the reverse of what a teleconverter does. A teleconverter DOUBLES the focal length while retaining the existing aperture. A wide converter, if it retains the entirety of the existing physical aperture, while shortening the focal length, results in a faster lens.
     
  8. KBeezie

    KBeezie Mu-43 Top Veteran

    697
    Sep 15, 2012
    Grand Rapids, Mi
    Karl Blessing
    From what I read of their white paper, it works primarily by delivering the light closer to the sensor so that there is less of a distance for light to fall off/degrade.

    Also from reading on how the Metabones adapters work, the lens needs to cover a larger CoC than the sensor, meaning it works best with non-native lens which is already designed to cover a film area larger than m4/3. The Oly 12mm is designed specifically for the m4/3 sensor and would face two problems.

    1) It'll vignette quite a bit, thus making the wider focal length pretty useless.
    2) Since the lens itself is already designed for m4/3 it's registration distance will be increased, as such infinity will be lost unless the adapter uses optics to correct for it... but then doing so might counteract the wide angle conversion.

    So in the sense of using it on an Oly 12mm, no go, and only a an adapter that gets closer to the Sensor will work (ie: the 12/2.0 is already pretty close to the sensor, it was after all designed for the micro-4/3 registration distance). You would have to use that kind of system with a non-native lens with a larger registration distance (canon, pentax, nikon, etc etc) that was a 12mm , you would basically end up with closer to a native 12mm field of view as opposed to a 24 if used without the optics.

    So back to what I was saying before, a WA convertor in the front of the glass, is never going to increase the light gathering.
     
  9. dougjgreen

    dougjgreen Mu-43 All-Pro

    Jun 5, 2013
    San Diego
    Doug Green
    And as I said, it wouldn't be in the front of the glass. But you can still put one in front of the glass and not LOSE aperture.

    None of the front-of lens wide converters that I'm aware of lose aperture. They simply don't gain it. But they essentially make a new, wider front element, that gathers MORE light than the target lens, and they concentrate (or focus, if you will) that greater amount of light into the target lens.
     
  10. tradesmith45

    tradesmith45 Mu-43 All-Pro

    Dec 13, 2012
    Oregon
    Hey guys, I love the theory - got a degree in physics after all.

    What I hoping for is comments from someone who's actually tried this already. The better converters are $150+. Reviews at B&H and Amazon (mostly from video use) say these converters are pretty sharp (except perhaps at the very edges).

    Wide field astrophotography is pretty demanding optically. Even a moderate amount of coma or astigmatism makes a mess of the image. Was at a Nat. Geo show of the 50 best photos of the West yesterday. One image of a sandstone arch in Utah w/ stars behind had a section of stars that was blurry. Don't know what caused the problem (perhaps a decentered lens) & it was a big print but it made my head hurt & I couldn't look at it.

    Don't want to spend a bunch of time & $$ w/ a converter & trip just to make lousy images. Most pros who shot the Aurora recommend UWA w/ F2.8 as the slowest lens you should use. That leaves me 3 choices:
    M.Z 12mm w/ converter (the lens is so good the combo might work well @ F2.8)
    An adapted Rokinon 8mm F2.8 Fisheye (I'd rather shoot rectilinear)
    Rent/buy an APS-C camera & Tokina 11-16mm F2.8

    So I'm checking to see if anyone has tried a converter on the 12mm. Some here have reported good results w/ the Panasonic converter on the 14mm.
     
  11. dougjgreen

    dougjgreen Mu-43 All-Pro

    Jun 5, 2013
    San Diego
    Doug Green
    I attempted to adapt the Olympus WCON-01 to the Panasonic 14mm lens, and I was NOT satisfied with the results for a specific reason - when attaching a wide converter to a lens it is not carefully designed to fit, one gets unpredictable results with respect to field curvature - which manifests itself in corners that are not in sharp focus when the center IS in sharp focus.

    I believe this is the likely (but not certain) result that you'll see when fitting either the Olympus WCON-01 or the Panasonic wide converter to the Olympus 12mm lens, as neither of these converters has been designed to fit, nor tested to work optimally with that Olympus 12mm lens. The odds that the coupling will be properly corrected at the corners at the same focus point that it's corrected in the center, are slim to none.
     
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