GF1 + 20f1.7 lens funny thing I don't understand

Discussion in 'Panasonic Cameras' started by pellicle, Sep 22, 2014.

  1. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    Hi

    I don't know this should be properly in another zone, because it could be camera or lens or even combo I don't know.While I've had m43 for some years, I've never had this combo of camera and lens before.

    However my issue is that using this combo I see that by simply facing the camera / lens towards brighter light it stops down the aperture without me changing or touching anything.

    It does this on all modes (such P or Av modes) and my focus is set to AFS

    is this behavior being triggered by some setting somewhere?

    Thanks
     
  2. agentlossing

    agentlossing Mu-43 Hall of Famer

    Jun 26, 2013
    Andrew Lossing
    It's common to all models, as far as I know. It keeps the sensor safe from heat damage from bright sunlight, and maintains a useful LCD readout.
    GX1•EP1•GF3•17/2.8•30/2.8
     
    • Like Like x 1
  3. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    so its common on the f1.7 lens? Does this mean that the 25 f1.4 has a similar behavior?
     
  4. agentlossing

    agentlossing Mu-43 Hall of Famer

    Jun 26, 2013
    Andrew Lossing
    It's the camera, not the lens, that triggers the aperture to close in bright lighting.
    GX1•EP1•GF3•17/2.8•30/2.8
     
  5. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    Hi

    except of course that it seems not to be. I waited till I could get home and confirm this, but of the three Panasonic lenses and 2 bodies I have it is only consistent with the 20mm f1.7

    neither the 14-45 nor the 14mm f2.5 exhibit this

    while the 20mm does it on both the GH1 and GF1

    interestingly, engaging 'shutter speed effect' halts this (as one would expect)

    So I feel that its a factor of the lens.

    It also alters how the thing takes pictures, with extra "clap ... clap clap" delays in picture taking even with the lens on manual focus.

    Its an interesting problem and I wonder if it contributes to people thinking the 20mm is a slow focuser (which it sort of is listening to the AF motor duration when going from close to infinity as well as watching the lens element move).

    I would wonder still if the 25mm f1.4 has this behaviour or not
     
  6. manzoid

    manzoid Mu-43 Regular

    137
    Jun 9, 2011
    I think it's an issue with fast lenses. The other ones you tried don't close to protect the sensor from all that light because the aperture is already smaller.
     
  7. agentlossing

    agentlossing Mu-43 Hall of Famer

    Jun 26, 2013
    Andrew Lossing
    Both of my lenses (17mm f2,8 and 30mm f2.8) do it.
     
  8. poopstick

    poopstick Mu-43 Regular

    112
    Aug 9, 2013
    Burlington Ontario
    Yes. The PL25 does it even more often than the P20.
     
  9. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    thanks for the info guys

    I'm unwilling to accept the "protection" angle because (looking at it) it stops down WAY more than f2.8 (to what looks to be f8 based on playing with shutter speed preview and A mode) and in and out of a few intermediate steps.

    IF the goal was to protect the sensor in some way then one would expect that when my f2.5 lens was pointed right at the sun it should stop down too ... but it doesn't move.

    IF f2.5 was sufficient for protection, why would it stop down more??

    anyway, at least "now I know" its not some setting that I've mis set.

    So like Julius I remain asking "why is it so"

    https://www.youtube.com/watch?v=LIfxV7uNZXQ

    :)
     
  10. manzoid

    manzoid Mu-43 Regular

    137
    Jun 9, 2011
    I don't know, maybe angle of view would be a consideration too? The 14mm would make the sun a smaller part of the overall image, so a larger portion of your image might be getting a lower intensity light.

    I think to test it scientifically you would need to make sure the light intensity hitting the sensor was the same. I don't know if it is just light related or actual temperature either.
     
  11. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    I expect that the 14-45 would cover that, and I did try it at many zoom settings.

    The aperture never , moved, facing straight at the sun too
     
  12. manzoid

    manzoid Mu-43 Regular

    137
    Jun 9, 2011
    The 14-45 isn't constant aperture, and is on the slow side though.

    If you just want to see if you can get the 14-45mm to 'rattlesnake', maybe try shining a high power flashlight directly onto it at close range, or the headlight of your car.

    I have to admit, I've only seen the problem myself with the 20mm. But it's the only native glass I have faster than 2.8. I have previously read about it with the 25mm PL, but remember hearing other lenses do it too. I think I remember usually hearing the complaint with the 25mm and Olympus cameras, so maybe it is both camera and lens dependant. That said, as mentioned above the sigma and Olympus lenses do it too.

    Edit - if you follow the flashlight advice, I take no responsibility for damage to your camera! ;)
     
  13. gochugogi

    gochugogi Mu-43 Veteran

    My 14 2.5 constantly stops down on my GX1 although in Av mode. Doesn't seem to do it on my E-P3.
     
    • Like Like x 1
  14. agentlossing

    agentlossing Mu-43 Hall of Famer

    Jun 26, 2013
    Andrew Lossing
    You can be "unwilling" to accept the protection angle but that doesn't mean it isn't a consideration of camera designers, even if it may not be the only one.
     
  15. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    I meant logically unwilling to accept that it applied. Truth is what it is - we don't know it yet. When we do then naturally I will accept that. As to me accepting a conjecture which does not fit the evidence, that is how deductive reasoning works.
     
  16. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    I see now that if I add the keyword rattlesnake to this search I find more hits. To me, reading many of those threads I see an emerging picture that points to firmware. Some combos rattlesnake while others don't

    interesting

    again, thanks for all the facts and pointers, been very educational