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Is a *fast focusing* 20mm f1.7 pancake feasible?

Discussion in 'Native Lenses' started by correos.e, Mar 30, 2014.

  1. correos.e

    correos.e Mu-43 Regular

    46
    Jan 25, 2012
    I loved my panasonic 20mm pancake - image quality and size. However, i sold it because of its awful low light focusing speed. I shoot my kids playing indoors and it just didnt work out. Oly 17 mm f1.8 fits the bill.
    But it's so much larger... I know there is a technical reason that makes the 20mm slow, my question is, is that the same reason that makes it small? Is it possible to have oly 17mm speed in a pamy 20mm size? I know the 17mm f2.8 and the 14mm... I'm asking about fast lenses, say, below f2
    Thanks!
     
  2. Jonathan F/2

    Jonathan F/2 Mu-43 Hall of Famer

    Aug 10, 2011
    Los Angeles, CA
    I'm sure Panasonic can make it small and fast, but they'd rather you buy the upcoming Panasonic Leica 15mm 1.7 or the PL 25mm 1.4.
     
  3. To make it one of the faster focusing lenses the 20mm would need an internal focusing design rather than the current unit focusing design (where the whole lens group moves to focus rather than a couple of lightweight elements). That means a fundamental redesign of the lens would be required.
     
    • Like Like x 1
  4. correos.e

    correos.e Mu-43 Regular

    46
    Jan 25, 2012
    Thanks penguin. I understand it would be a major redesign. My question is: does the current unit focusing design contribute to the smaller size and the internal design would make it larger, or can we technically have a very small internal design?
    Thanks!
     
  5. duke

    duke Mu-43 Veteran

    420
    Dec 4, 2010
    Tulsa, moving to Houston
    Duke
    The panasonic 14mm f2.5 is tiny and incorporates an internal focusing mechanism, so it can be done, just probably wont for a while :(
     
  6. MAubrey

    MAubrey Photographer

    Jul 9, 2012
    Bellingham, WA
    Mike Aubrey
    Probably? Without an optical designer we cannot say for sure, but the testament of the 17mm f/1.8 and the forthcoming 15mm f/1.7 suggest that it would be larger.

    Minimally, you need to incorporate extra space inside the lens for focusing. You can see the space difference between the 17mm f/1.8 and the 20mm f/1.7:

    20mm
    c_020mm_f017_panasonic.

    17mm
    c_017mm_f018_olympus.

    That group of three elements in the back are the focusing group (the two asphericals and one other just before the final rear element). Internal focusing also requires more lens elements for the focusing group (and correcting the focusing group) as well, which would also contribute space--and even after those corrections, then the 20mm is still sharper. The kind of focusing in the 20mm where you move the entire lens forward and back, is extremely effective for resolution in a compact size, but not great for speed.
     
    • Like Like x 1
  7. usayit

    usayit Mu-43 Hall of Famer

    Anything is possible with time and cost.

    I am kinda hoping they leave it as is.... let the R&D costs recup and lower the price. Then maybe those that complain that MFT stuff is too expensive will stop.
     
    • Like Like x 1
  8. Steven

    Steven Mu-43 All-Pro

    May 25, 2012
    USA
    I've been asking that question for a long time . Based on the fact that newer lenses from both companies, like 17/1.8 and 15/1.7 are larger , I am guessing it is not possible :(
     
  9. klee

    klee Mu-43 Veteran

    367
    Mar 20, 2013
    Houston, TX
    Kevin
    In my experience the 20mm's focusing motor is controlled more smoothly and quickly by panasonic bodies already.
    the GH4K's new "depth of defocus" algorithm may actually improve the focus speed even more.

    I don't know why Olympus hasn't bothered to make any fast aperture pancakes.
     
  10. DekHog

    DekHog Mu-43 Top Veteran

    579
    May 3, 2011
    Scotland
    As Duke stated above, they managed it fine with the 14mm, so I can't see a reason why they couldn't do it with the 20mm with a redesign .... that doesn't mean they will. I think they would have done it before now if they were going to.

    It's a very sharp little lens, but is the one I pick up less than any other due to the focus speed.
     
    • Like Like x 1
  11. Steven

    Steven Mu-43 All-Pro

    May 25, 2012
    USA
    I am guessing that wider angle lenses like 14mm can be kept shorter. Also , it is significantly slower aperture than 1.7.
     
  12. MAubrey

    MAubrey Photographer

    Jul 9, 2012
    Bellingham, WA
    Mike Aubrey
    If we look hard enough we can see a number of reasons why.

    The 14mm is only 14mm and only f/2.5. That means it only needs a entrance pupil of 5.6mm, while the 20mm f/1.7 requires 11.7mm, more than twice as large. The 14mm has the space for internal focusing because of those super tiny elements. The 20mm simply doesn't have that luxury. The 14mm also sacrifices some sharpness, too. It's nowhere near as sharp as the 20mm.
     
  13. DekHog

    DekHog Mu-43 Top Veteran

    579
    May 3, 2011
    Scotland
    Very true, I never took the max aperture into account.