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Using focal reducers with GH1/2 and old lenses?
  • PsycoPsyco
    Hi!

    As I dont like the result of using wide angle adapters and it is not easy to find cheap bright and wide lenses, I did some tests with a focal reducer.

    The idea is, to use the much bigger image circle of the full frame lenses and squeeze it onto the m4/3 sensor. As a result this would give more light and more angle of view. As there is enough space between the backend of the lens and the image sensore, it would be possible to modify this cheap adapters (like Nikon/Canon/.. to m4/3 adapters you find on ebay) to fit a focal reducer in it. This would not only set the angle of view back to what you will get on a full frame DSLR, but also brighten the image by the same factor!


    After some testing with my GH13, Antares 0.5x 2" focal reducer and Minolta MD Rokkor-X 50mm f1:1.4 ...
    image

    Test Image without reducer at high F-stop (sorry for the boring subject;-):
    image

    Same lens, high F-stop, same setup but WITH focal reducer:
    image
    Obviously, the field of view is wider - just not as much as I like it to be. But a "stronger" focal reducer might solve that problem. The image is also brighter - in this case I used a different shutter speed - which was pretty much what I expected.

    But as we all know, high F-stops are not what we want. Same setup, same lens without focal reducer, but at F1.4:
    image

    And finally the lens at F1.4 WITH focal reducer:
    image
    Wider field of view, brighter image but horrible IQ. The white glow is known as coma (thanks to hopeless_4ever for that information).

    There are also coma correctors out there, but there is not enough space between the lenses to fit one of these also in there.

    Bitcrusher did some very interesting tests with the rear element of a Tokina lens. Hopeless_4ever also pointed out, that Olympus did reworked some lenses with focal reducers to fit m4/3 - so, it is possible.

    These last bits of information point in a promising direction, but there is still a lot of things to test and think of.

    If we could find a setup to project the full frame image circle in good quality onto the m4/3 sensor, we wouldn't need the crop mode on the GH2 and the tiny c-mount lenses or buy the very expensive m4/3 lenses...

    ...but the ultimate goal would be a 1.5x anamorphic focal reducer - small, not as expensive as a full lens and the choice of the main lens would still be up to us!

    Hopefully someone has a good idea, as how to proceed from here. Focal reducers with stronger light bending exist, but without solving the coma-problem, that doesn't get us closer to something usefull.
  • 61 Replies sorted by
  • Xenocide38Xenocide38

    Tried out one of the cheap $100 speed booster knockoffs with a GH2 http://www.stronzvanderploeg.net/100-speed-boosterlens-turbo-test/

  • Tom3DTom3D

    I'd still be interested to hear your progress. The speedboosters aren't very high magnifications, only 0.7x 0.5 seems like a more powerful reduction.

  • coagulosocoaguloso

    @Brian202020 well the price of those adapters is really out of my budget... Let´s expect for the lens turbo to be very cheap.

  • Brian202020Brian202020

    I abandoned the work when there was a rumor of the Speed Booster. It's harder than you think. I say let the professional make them now that they exist.

  • coagulosocoaguloso

    Is there any information from that guy @Brian202020 ?, i really want to build something similar, with a 0.5x focal reducer, making any FF lens adapted to m43 while keeping the focal length, i am planning in buying the same focal reducer and build something similar, i am not a serious photographer, but i like to play with lenses so quality is not an issue, also i have a Olympus OM 55mm F1.2 i would like use, it is very soft already so maybe mantaining the focal length will keep the softness away, i don´t know...

  • Vitaliy_KiselevVitaliy_Kiselev

    @jleo, we have separate topic now

    http://www.personal-view.com/talks/discussion/5770/metabones-lens-speed-booster

  • jleojleo

    Metabones Speed Booster

    Philip Bloom: The Metabones ‘Speed Booster’ is a 0.71 x focal reducer, that will effectively turn your full frame 50mm f/1.8 lens into a 35mm f/1.2 lens

    This version is of the ‘Speed Booster’ is optimised for the NEX so it’s not just a case of putting it in a different housing. But the good news is that Metabones plans shortly after initial release, other camera mounts will follow, the Micro 4/3 and the Fuji X-mount and others in the future. That has some exciting possibilities! for the Micro 4/3 Black Magic Cinema Camera and the Panasonic GH3 ...

    http://philipbloom.net/2013/01/13/speedbooster/

  • GH2_fanGH2_fan

    @mnryan @Brian202020 Anything at all?

  • GH2_fanGH2_fan

    Well, it's been well over 2 weeks now, I was wondering if there are any updates inregards to this? :D

  • SeamlessMediaSeamlessMedia

    I've been very interested in this as well, from what I have read, the only reason that there aren't plenty of manufacturers making micro four thirds adapters with .5x focal reducer built in, is because Kodak holds the patent on them. I did have an idea I wanted to share for those experimenting with this, there seems to be difficulty in the different optical formulas of various lenses and how and where to place the reducer lens in the optical path for the desired result. Consider this, the one constant in the optical path of a lens design is the distance from the lens mount to the sensor. If you construct a tube/adapter that places the reducer optics at the specific distance from the mount where the sensor would be, you should be able to "capture" the light path with a known size and focal plane, specifically the size and focal plane that the lens was designed for and the sensor expects to see. I understand that the angle of the optical path coming from the last element of the lens may vary, but I just wanted to throw the idea out there and see if it helps. Granted placing the reducer optics at that point will make the overall construction of the adapter quite long and cumbersome.

  • DirkVoorhoeveDirkVoorhoeve

    Hey guys, you could also use the coma as a style, like in eat pray love:

  • mnryanmnryan

    @GH2_fan I'm pretty sure Brian just said he'd be another week or two yet with updates.

  • GH2_fanGH2_fan

    So...any updates? :D

  • Brian202020Brian202020

    @peterosinski

    The P+S Tenhnik Pro35 adapter is the first 35mm lens adapter made. The M2, M3, and Letus adapter were based of that. It uses a oscillating ground glass as a mini screen inside it to record the image off of.

    Also my tests will have to wait another week maybe 2. I'll keep you all updated.

  • peterosinskipeterosinski

    http://www.abelcine.com/store/P-S-Technik-PRO35-Digital-Image-Converter-for-2-3-Cameras/ looks like there is an existing product that acts similar to a focal reducer, but at the cost of a mid size sedan

  • kriskris

    I apologize for my bad english!!! Welcome the idea of ​​Focal Reducer, but there is no danger of a little softness in the corners of the frame- reduced visual acuity in the periphery? Thank s!

  • GH2_fanGH2_fan

    Please do let us know, I think the whole Focal Reducer thing is absolutely great, in my opinion, it actually restores the original focal length of any lens that is used on the GH2 due to the crop factor/sensor size.

    I really do wonder if there is one that will make us able to use lenses at wide apertures like f1.8 or lower without any image degradation.

  • GH2_fanGH2_fan

    Please do let us know, I think the whole Focal Reducer thing is absolutely great, in my opinion, it actually restores the original focal length of any lens that is used on the GH2 due to the crop factor/sensor size.

    I really do wonder if there is one that will make us able to use lenses at wide apertures like f1.8 or lower witho

  • Brian202020Brian202020

    Got my last part today actually. I will assemble everything next week and do tests.

  • peterosinskipeterosinski

    any updates yet?

  • Brian202020Brian202020

    @peterosinski

    My parts haven't all arrived yet. I purchased them on ebay and their shipping and handling seem to be slow. I'm hoping to get everything soon.

  • peterosinskipeterosinski

    updates?

  • peterosinskipeterosinski

    @brian2020 is it possible that the reason you had no coma in the pictures where you shot your face from a low angle is because the 3.5 f stop is already relatively small? Did you have a chance to try it out with a faster lens?

    edit: sorry I saw psyco already asked the same question. That being said, the 3.5 should still show up as a 1.8 when used with a reducer right?

    edit 2: in the before and after pictures you posted using the 20mm f3.5 how can it be that the exposure remains the same when using a focal reducer if you said you had the lens wide open and we can see that your shutter speed and iso remained the same

  • JohnBarlowJohnBarlow

    Have you tried a positive acromat? SurplusShed has some cheap ones for testing

  • Brian202020Brian202020

    I won't be heading to my office to get another lens until after the weekend, and hopefully by then I'll have the rest of my parts to make the adapter. The link below is the Focal Reducer I'm using. Also note that in order to make the flange distance small enough I had to actually remove the glass itself from the housing.

    http://www.ebay.com/itm/221125028103?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

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