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metabones speedbooster for native lenses?

Discussion in 'Native Lenses' started by travelbug, Oct 27, 2015.

  1. travelbug

    travelbug Mu-43 Regular

    138
    Oct 20, 2014
    im new to (topside) photography and mft in general,but reading about the metabones speedbooster, wouldnt native lenses benefit from this too. from what ive gathered, a speedbooster would give us an additional stop, decrease the crop factor, will not introduce additional aberrations/degrade image quality and maintain fly by wire control. maybe im missing some big con of the system, but wouldnt this be a good thing even for native lenses?
     
  2. Speedliner

    Speedliner Mu-43 All-Pro

    Mar 2, 2015
    Southern NJ, USA
    Rob
    The focal reducers work by concentrating the light circle intended for a larger sensor down to MFT size. That msjes the image brighter. Like a magnifying glass will do with sunlight. you've probably done that.

    Since native lenses don't have a larger image circle they can't be concentrated. Magnified like a TC, but not concentrated to create a brighter image.

    I do wonder if the deeper flange distance of 4/3 lenses provides an opportunity for some concentration but I doubt it. Probably not enough to make a difference and provide any value.
     
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  3. MarkRyan

    MarkRyan Instagram: @MRSallee

    772
    May 3, 2013
    California
    It wouldn't work for native lenses, for two reasons.

    (1) The Speed Booster fits between the back of the lens and the lens mount. With legacy lenses, there's plenty of room between the back of the lens and the mount, which is otherwise occupied by an adapter. With native lenses, there is zero room between the back of the lens and the mount.

    (2) Native lenses project too small an image circle. The Speed Booster works by taking the larger, full-frame image circle and compressing it onto the smaller sensor. With native Micro 4/3 lenses, there's a good chance the lens does not project an image much larger than the Micro 4/3 sensor. Compressing it further would simply result in heavy vignetting (black edges).
     
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  4. travelbug

    travelbug Mu-43 Regular

    138
    Oct 20, 2014
    thanks for the explanation
     
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  5. travelbug

    travelbug Mu-43 Regular

    138
    Oct 20, 2014
    just a follow up question, if the native lens is projecting an image circle that is the same size as the sensor, then why are we still getting the 2:1 crop for then?
     
  6. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    The sensor is smaller than 135, thus a shorter focal length is equivalent in field of view to one roughly two times it's length. The lenses in question may be a shorter focal length however they're designed for the smaller image circle and do not project one for the larger format.
     
  7. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    We aren't actually getting a 2x crop at all. It's really just an awkward shorthand so that people who are used to shooting 35mm film cameras can understand what the field of view is by multiplying the M4/3 focal length by 2.

    When digital SLRs first came out the sensors were extremely expensive, so they could only make them at APS-C size, but there weren't any lenses available that covered that field of view, but plenty of lenses designed for 35mm film cameras. So they called them "crop" cameras, because the sensor was just capturing a 1.5x or 1.6x cropped portion of the image circle projected from the "full frame" (135 / 35mm format) lens.

    Today, by contrast, most lenses available for APS-C cameras on the market will only cover APS-C sensors. They aren't truly a 1.5x crop, just like 4/3 and M4/3 cameras aren't actually a 2x crop. They are totally native lenses, designed and optimized specifically for a system that happens to use a smaller sensor. This has pros and cons, but that's a conversation for another (1000) threads...
     
  8. MarkRyan

    MarkRyan Instagram: @MRSallee

    772
    May 3, 2013
    California
    The size of the projected image circle is independent of both (a) the focal length, and (b) the field of view.
     
  9. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    I've always wondered: if I take a medium/large format lens and build a specific focal reducer for it should I gain 2 or maybe 3 stops, right? :)

    Is this about what happens when I connect the camera to a big telescope?

    And should I also be able to do a medium format -> full frame speed booster? Is there any one around?
     
  10. RnR

    RnR Mu-43 All-Pro

    Sep 25, 2011
    Brisbane, Australia
    Hasse
    I have never seen one. Not sure on the available image circles from astronomy type gear, but they do use focal reducers in astronomy a fair bit. Perhaps one could be adapted.
     
  11. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    I'm sure you could make one, but I'm not sure how much appeal it would have. Most Medium Format standard lenses top out around f2.8. I guess there's that one Mamiya 645 80mm/f1.9, but then you'd be buying a $350 420g lens to turn it into a 58mm/f1.4, of which there are plenty...

    I guess you could turn a Pentax 105/2.4 into a 75/1.7, which would be pretty cool. Though that's already a 600g lens...
     
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  12. Petrochemist

    Petrochemist Mu-43 Top Veteran

    652
    Mar 21, 2013
    N Essex, UK
    Mike
    Both correct but reason (1) is actually worse than that.
    A focal reducer makes the distance from lens to image shorter, not only does it need to fit in zero space but it has to reduce it to a shorter distance still. It might somehow be possible to fit a focal reducer within the mount but the lens would be too far away for infinity focus, it would no doubt foul may of the native lenses & the vignetting would be terrible. It's usefulness would very questionable even if it didn't require any effort to design.
     
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