12-35mm X - Constant Aperture through Zoom?

Discussion in 'Native Lenses' started by thebmillz, Sep 1, 2012.

  1. thebmillz

    thebmillz Mu-43 Rookie

    12
    Aug 31, 2012
    Apologies if this is a stupid question.

    One of the reasons I was excited about the 12-35mm lens was the idea it would have a constant aperture, so that I could do a slow zoom on a character and I wouldn't see the light change or flicker. But, it's definitely happening with this lens.

    Check out this video:
    https://vimeo.com/48662408
    password: 1235

    I've messed around with the exposure settings in movie mode. But, all of them do the same thing. Am I doing something wrong? Or was I wrong to expect this lens to do that?

    PS. It should be noted: I used the new "Apocalypse Now" hack with the lens: personal-view.com/talks/discussion/4391/apocalypse-now-quest-for-simulated-444-smooth-cinema-quality-driftwood-cbrandin-bkmcwd?Sort=newest
     
  2. arad85

    arad85 Mu-43 Veteran

    477
    Aug 16, 2012
    Umm.. It's your camera altering the aperture, not the lens. You may need to upgrade the camera not the lens ;)
     
  3. thebmillz

    thebmillz Mu-43 Rookie

    12
    Aug 31, 2012
    If the GH2 isn't capable of it, what would be?
     
  4. mattia

    mattia Mu-43 Hall of Famer

    May 3, 2012
    The Netherlands
    Are you shooting full manual? i.e. fixed shutter and fixed aperture rate? If the camera is doing any metering, exposure will shift as the content of your image (proportion of light and dark areas) changes.
     
  5. thebmillz

    thebmillz Mu-43 Rookie

    12
    Aug 31, 2012
    Everything is set to manual. Unless there's a setting I don't know about.
    I even tried taking the camera outdoors and the camera didn't adjust the aperture for that. (stuff was blown out)
     
  6. meyerweb

    meyerweb Mu-43 Hall of Famer

    Sep 5, 2011
    You're correct -- this is NOT a constant aperture zoom

    The aperture adjusts in discreet steps, at specific focal lengths. In between those steps the effective aperture changes gradually as you zoom.

    I noticed this today. I just got my 12-35, mounted it on the camera, and noticed that as I zoomed from 12mm toward the long end the lens made a clicking sound about half way between the 18mm marking and the 25mm one. I wondered what the heck was making the click. A bit later, I tried doing this again, after the camera had gone to sleep, and there was no click. Wake up the camera, and there's the click again.

    I then turned the camera around so I could look in the lens while doing this. I discovered the click was the aperture adjusting size as it passed that point. And there are several other points at which the aperture does a discreet step adjustment, no matter which direction you zoom in. With my Canon constant aperture zooms, the aperture adjusts continuously, or at least in steps that are fine enough you can't tell the difference.

    Sadly, this lens is NOT continuously compensating the aperture as focal length changes. It makes several discreet adjustments as you move through the zoom range.

    The OP is not doing anything wrong. What the OP's video is showing is the image gradually darkening as he zooms in, then suddenly brightening as the lens reaches the point where the aperture adjusts. I'm very surprised, but this is NOT a constant aperture 2.8.

    I don't really care about video, so this doesn't bother me much. But I can see this as a real issue for video shooters who zoom during shots. More to the point, though, is that Panasonic's advertising is false. Their specs say: 'Top-quality optics combined with a large non-variable maximum aperture produce sharp,lifelike images with one control, as desired by professionals.'

    http://content.meridinet.com/pub/Panasonic/spec-sheets/camera-lens/PCEC4503-4_LumixSS_Lens_LR.pdf

    This simply isn't accurate. The aperture visibly changes in steps, and does not maintain a constant, non-variable maximum aperture as you zoom. Try this yourself, while looking into the front of the lens.

    Question for the OP: does this still happen in Aperture preferred mode? I wonder if the shutter speed will vary to maintain a constant exposure.
     
  7. thebmillz

    thebmillz Mu-43 Rookie

    12
    Aug 31, 2012
    Hi meyerweb,

    I tried aperture priority with no luck.

    That clicking noise thankfully goes away during video shooting, but the flaw I spoke of before is still there. In fact, I shot some outside stuff here and yet again it creeps up:
    https://vimeo.com/48673906
    password: 1235

    My apologies for the yapping dog in advance.

    Considering the existence of the Panasonic AF100 and the rumors surrounding the GH3 being more "pro video shooting friendly" - I thought for sure this would be "the lens". Couple that with Panasonic's advertising and well...This just sucks.

    I hope there's something in camera I'm missing, but if not, I'll have to send it back.
     
  8. ptolemyx

    ptolemyx Mu-43 Veteran

    290
    Jun 19, 2012
    Vancouver, BC
    Ben
    Nevermind. Out to lunch.
     
  9. ptolemyx

    ptolemyx Mu-43 Veteran

    290
    Jun 19, 2012
    Vancouver, BC
    Ben
    More blather to ignore. :)
     
  10. thebmillz

    thebmillz Mu-43 Rookie

    12
    Aug 31, 2012
    I've zoomed in and out at 2.8 and stops up to 8. They all have the same problem. The last video I did was in daylight. Another early video someone posted had the same problem and it was in broad daylight. I've seen that help link you posted before (I've been trying to figure this out for the last 24 hours). I've reset my camera, etc.

    Via that site:
    "To get a constant f-number while zooming with the Lumix 14-42 and 14-140 lenses, zoom out all the way and then set the aperture setting to the widest setting available at the longest focal length you intend to use, e.g., 5.8 for 140 mm. It won't be a truly constant f-number, but the camera will approximate it by adjusting the aperture in increments as you zoom in and out."

    Not sure how that applies to me here... if it's supposedly 2.8 at every focal length. And heck, at 8, it's still doing it.
     
  11. ptolemyx

    ptolemyx Mu-43 Veteran

    290
    Jun 19, 2012
    Vancouver, BC
    Ben
    Sorry, I'm being dumb. Of course the physical size of the aperture changes as you zoom; f2.8 is wider at 35mm than it is at 12mm. Ahem...

    I failed to see meyerweb's point, which is that a constant aperture is not maintained at focal lengths in between the aperture steps; the adjustment would have to be stepless for that to be the case.

    Anyway, it's still possible that the fault lies with the camera--that it's incapable of adjusting the lens steplessly, as opposed to being a limitation of the lens itself. But yeah, I'm surprised that Panasonic hasn't got this sorted.

    I'll go crawl back under my rock now...
     
  12. thebmillz

    thebmillz Mu-43 Rookie

    12
    Aug 31, 2012
    It's all good. I'm no professional by a long shot.

    I'd be really curious how this lens acts on an AF100, since that camera is specifically made for video. If it doesn't work there...
     
  13. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    Wow, bummer. The lens still suits my needs fine, but any idea how high the aperture can get before the next adjustment?
     
  14. jnewell

    jnewell Mu-43 All-Pro

    Jun 23, 2011
    Boston, MA
    The term "constant aperture zoom" goes way back before anyone put video into a "still" camera (or before the categories got blurred). It's supposed to be essentially a math fact, not a video-related attribute. It is sort of surprising that with all the attention being paid to zoom lenses set up for video use with quiet motors, etc., that this problem hasn't gotten more focus (pardon the pun).
     
  15. CPWarner

    CPWarner Mu-43 Veteran

    244
    Dec 24, 2010
    Cliff
    Interesting. I tried this with my 12-35mm and found I have a louder click at just about 14mm. No noise between 18 and 25mm. I see 4 steps in the aperture when I look at the front like you did. They are at 14mm, ~16mm, ~20mm, and 25mm. I guess our lenses are slightly different in that one step is louder than another on different lenses.

    EDIT: I tried this at f/2.8, f/5.0, and f/8 and the aperture steps were at the same places.

    I agree that I would have thought that they would adjust these in smaller steps than that. If you have the setting "Live View Boost" set to off on the OMD, one can see the screen change in brightness with zooming associated with these steps. I can live with it as I do not shoot video, but that is disappointing that they did not implement an aperture control with finer resolution considering the cost of this lens. I wonder if they can improve this with a firmware upgrade as it is an electronic aperture or if it is a consequence of the aperture control?
     
  16. thebmillz

    thebmillz Mu-43 Rookie

    12
    Aug 31, 2012
    @jnewell - I don't want to belittle the lens just because it's not living up to my standards as a videomaker. BUT - Panasonic is no doubt in the videomaking business and I thought I'd get a lens that could handle long zooms like that and be able to autofocus fairly quickly (for run and gun situations) and I don't even feel that part of the equation is that wonderful.

    The stabilizer in the lens seems pretty good though. If I walk around at 12mm, it feels nice and floaty almost.

    Honestly - I'm contemplating sending this back and getting that little 14-42mm compact lens: Amazon.com: Panasonic Lumix G X Vario PZ 14-42mm/F3.5-5.6 Lens for Panasonic Lumix G-Series Digital Cameras (Black): Camera & Photo If all zooms display this type of problem, I might as well get something that's compact that I'd take out and use traveling more. Then, maybe get a really fast wide prime lens. I had sold my 20mm pancake and 14-42 kit lens, thinking that this 12-35 would solve all my problems as a videomaker, but alas...

    The focus and zoom ring are silky smooth though!
     
  17. Bruce.B

    Bruce.B New to Mu-43

    2
    Sep 4, 2012
    It changes, currently Maine
    Bruce
    If you want a credible answer, this is probably not it, but if you'll settle for IN-credible, 2 things come to mind. Either or both can produce a visible effect in the image...

    - if there's a clicking noise at predictable zoom positions (btw, is it picked up in the audio?), the issue is in the lens. The camera controls aperture for exposure, but not for geometry compensation. The latter is controlled by lens f/w. I'd speculate a bug in the lens f/w was causing the audible 'click'. Whether a mechanical or electrical source, it's specific to the lens.

    - what's your ISO setting? Auto by chance? I'm not sure how your camera's firmware is designed, but at least some Manual modes are mechanized in a way to allow operator control of Aperture and Shutter speed but leave ISO set to Auto. Depending on your metering settings (spot vs. multi-point), an evenly lit scene will likely not change the amount of light hitting the sensor as you zoom in/out or pan, but a scene with a lot of contrast may have a varying amount of light hitting the sensor which can affect the processing engine's calculation for ISO. If Auto ISO is active, whether intended by the mfr or not set by you, you'll see it in the image. If Auto-ISO is active, a different camera might produce different results if that camera leaves ISO fixed. Or maybe you can set ISO to a fixed value.

    Since you mention both situations, i.e. clicking noise as you zoom and varying brightness of the recorded image, you may have both situations.

    This is all speculation of course... I don't have your camera nor your lens.
     
  18. stoneinapond

    stoneinapond New to Mu-43

    2
    Sep 4, 2012
    Greetings,

    There does seem to be an issue with the aperture adjusting in a stepped manner during zooming in video mode. My steps seem to occur at around 15 and 23 mm approximately, accompanied by a click. I'm using the camera in full manual mode and I notice that the histogram is also changing at these points.

    I tried AF/AE lock, but it makes no difference.

    Does anyone know if there is a place to communicate this to Panasonic? And if anyone who has this issue is on Facebook, can you send a message there to see if this is something they are aware of and is fixable?

    If not, I may regretfully have to return the lens. Really don't want to.
     
  19. thebmillz

    thebmillz Mu-43 Rookie

    12
    Aug 31, 2012
    The stepping sound only happens when you're taking stills. Once you're shooting videos it stops.

    I couldn't find any help via Panasonic and ended up returning the lens to Amazon.
     
  20. arad85

    arad85 Mu-43 Veteran

    477
    Aug 16, 2012
    Now I have this lens, I also see the 4 steps. Looking down the lens with the camera off, the aperture increases linearly and smoothly with the moving of the zoom ring meaning the clicks and flicks are not mechanical but driven by the lens/camera combination (I have a G5 here). What I think is happening is that as you zoom, the limiting aperture ring (the one that grows smoothly when the camera is off) grows to reveal the aperture blades behind the aperture. Once you get to a certain amount revealed, the lens decides to pull them back and this is where the "flick" happens.

    I suspect a lens firmware issue - the aperture does constantly vary mechanically, it doesn't do it as smoothly electronically. Switching the camera off with the lens very close to the click points with a little of the aperture blades visible and they immediately jump back behind the opening.

    As far as I can see the 7-14 doesn't do this. Unfortunately, those are the only two Panny fixed aperture zoom lenses available so comparisons with other lenses is difficult :(