14-140 exposure shift during zoom?

Actually, I take that back. The exposure fluctuations can happen during slow zooms as well, they're just more subtle. But you can see them if you watch the zebras carefully. The lens does manage to hold focus on slower zooms, though.

I'd really like to hear if more people are experiencing this same thing, either with the 14-140 or other micro4/3 lenses. I've never seen this sort of thing happen with any other zoom lens, be it a still photo lens or video lens, constant aperture or not, parfocal or not. Is this a widespread issue with m4/3 lenses (in full manual mode)?
 
On the Oly zooms the iris glitch occurs no matter how fast you turn the zoom ring. You can see & hear the iris change as well as see the numerical f/stop change in the LCD/EVF.
 
Just saw someone in another thread mention that this happens with the Panasonic 14-54mm on the AF100 as well. So my next question is; why this happening, and will it be possible to fix this with firmware or not? (Do these lenses do this on the GH1 and GH2 as well?)
 
Ljung said:
...you can see the lens isn't able to keep up and seems to lose track of both the focus and the exposure simultaneously, if only for a moment. It's a very odd thing for a lens that is supposedly optimized for video to do.
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Panasonic and Olympus auto-focus zooms do not function like traditional manual zoom lenses which maintain precise focus and aperture settings by mechanical design. Four Thirds lenses are not designed to hold focus and aperture while zooming - they are utterly dependent on active electronic compensation to dynamically correct their inherent shortcomings. Even the slightest touch on the zoom ring will disturb both focus and aperture settings, forcing the camera to revise its internal lens adjustments.

When you zoom an auto-focus lens during a video take, the camera immediately detects the aperture change and loss of focus-lock and attempts to correct it. However, continuous zooming will repeatedly invalidate the camera's attempts to correct the aperture and regain focus-lock, forcing it to abort and retry its lens adjustment procedures over and over again. If you zoom quickly enough, the camera will simply fail to keep up with your pace, and the lens will visibly drift out of focus until you pause and allow the camera to catch up. This hazard is particularly severe with the Lumix 14-140mm due to its extremely wide zoom range.
 
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hi all. first post, but i have been reading these threads for weeks. (great work by the way). i got my agaf101 and gh2 a week or so ago. having the same problem with the 14-140. am i being a huge div, or is this not a massive deal breaker?!? if you cannot zoom in full manual mode without exposure and focus fluctuations, aren't the lenses useless? it's all making my head hurt at the mo. ha!
 
Think about it. If the lens is a 14-140 f4-5.6 guess what would be the NORMAL reaction of the aperture if you zoom in? That is an easy one.
 
To John, and others who don't know what we're talking about here, but are compelled to offer theoretical observation, you don't know what you're talking about here. What this lens does is fluctuate, rubber-band its exposure behavior during any kind of zooming. In other words, when you zoom out, the effective exposure darkens, the lightens, very quickly, elastically. This is not just an optical phenomena, it's a characteristic of the lens's inner workings. It makes the lens useless for any kind of intended snap zooming - as not only iris but also focus fluctuate, I would say "wobble", back and forth as you change focal length. Not a good characteristic for a video lens, but then again, I think we've heard Jan and Panasonic stay away from calling the 14-140 a "video" lens, and they've definitely avoided calling the AF100 an ENG camera.
 
There is fluctuation during the zoom movement. If you use it as a variable prime, it'll always settle in where you want. But as you travel, it fluctuates.

Nature of the beast, I'm afraid. It's a $700 lens that does a million things automatically; it doesn't appear to do them all perfectly. If you want perfectly stable zoom & iris, you can get the Red Pro 18-85 zoom, but note that that's $10,000. And about 10 pounds.

If this was marketed as an ENG camera, and the 14-140 was marketed as an ENG lens, I'd say they were both pretty mediocre to lousy for that job. But it isn't, and I still say that if you had to do that job with an AF100 (and I would recommend against it) but if you HAD to, the 14-140 is still the best game in town. It's got the zoom range, the OIS, and the autofocus that make it the best substitute for a video camera lens that we can currently get, and it's cheap.

But no, it's not an ENG lens, and you're ideally not going to be doing a lot of zooming during a shot with it. If you absolutely need a low-cost, perfectly-zooming camcorder, the AF100 isn't it, you should be looking at the HMC150, HPX170, HMC40, HMC80, or any other designed-for-ENG camera.
 
I think there is some complaint exhaustion going on here, and everyone is getting touchy, but I have to say this thread has been useful. I personally like to know the limitation and why. When I noticed it during a shoot I wasn't mad, or feeling cheated...I just made a note to myself not to do that again and figure out what was going on. Sure enough I had exceeded a limitation of the camera lens combo for that use. This thread, especially a few posts up was very useful for that.

Our 500 was too big to strap to my back and go snowboarding with, so we used the 100, which is why I like it. It actually did very well, though I will not use that lens again for that kind of shooting. At least not for any zoom. Frame and shoot and it's fine.

It's actually worked quite well for us as an ENG camera and I"m thrilled with it, though I know of more than a few situations where our 500 would be the only option. On the other side I know a bunch of situations where our 500 would stay in the locker and we'd use the 100. The Panasonic 600 is a dream bit of kit.
 
True, a large-sensor camera might not be the best choice for ENG-style shooting, but the fact that the 14-140 includes fancy autofocus capabilities and OIS seems to indicate that it's not really intended for controlled, cinematic style shooting either. I suppose it's disheartening for me to see that Panasonic appears to have chosen to sacrifice the consistency of exposure/focus while zooming in exchange for automated features that most of us who enjoy large sensors don't really want anyway.

And I'm curious if the sacrifice is necessary; I've used the Tamron 17-50mm VC, which offers autofocus (for stills), image stabilization, stable exposure while zooming (and constant aperture covering a slightly larger sensor to boot), at a price point less than the Panasonic 14-140. Is it the "continuous autofocus" in the Panny that's the culprit? The fact that the glitch occurs with other m4/3 and 4/3 lenses seems to indicate not.

I guess the next question for me is, does there exist a zoom lens that can go at least as wide as 14mm, cover the 4/3 sensor, and handle predictable in full manual mode? If not, someone should build it. Go!
 
Ljung said:
True, a large-sensor camera might not be the best choice for ENG-style shooting, but the fact that the 14-140 includes fancy autofocus capabilities and OIS seems to indicate that it's not really intended for controlled, cinematic style shooting either. I suppose it's disheartening for me to see that Panasonic appears to have chosen to sacrifice the consistency of exposure/focus while zooming in exchange for automated features that most of us who enjoy large sensors don't really want anyway.
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Well you'd have to ask yourself -- who did they build that lens for? Certainly not cinema shooters! That is the kit lens off the GH1, which was the first consumer stills camera that had a usable, "real" video mode. And it was because of that lens.

I guess the next question for me is, does there exist a zoom lens that can go at least as wide as 14mm, cover the 4/3 sensor, and handle predictable in full manual mode? If not, someone should build it. Go!
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The Olympus 14-35 is probably more along the lines of what you want.

But still, you have to understand something -- NONE of these lenses have been built for video purposes. The 14-140 is the closest to a video-style lens that's been made. The Olympus lenses are big, fast, and sharp, but they're SLR lenses through and through.

If someone someday builds a purpose-built HD video lens that is designed from the ground up to handle all the video tasks, then yes that would be the time to start looking at an AF100 as a true crossover. Until then, m43 lenses are stills lenses that are borrowed into a video world.
 
While I don't yet have an AF-100, I have a Panasonic G2 which supports AFS auto-focus mode on most Four Thirds lenses, as does the GH2. I conducted a quick zoom test of the Olympus 35-100mm f2.0 lens in manual focus mode, with exposure set to f3.5, 1/60 sec, ISO800. See if you can spot any fluctuations in exposure:

 
A quick zoom test of the Olympus 14-54mm f2.8-3.5 Mark II lens in manual focus mode on the Panasonic G2, with exposure set to f3.5, 1/60 sec, ISO800. See if you can spot any fluctuations in exposure:

 
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A quick zoom test of the Panasonic 14-50mm f2.8-3.5 lens in manual focus mode on the Panasonic G2, with exposure set to f3.5, 1/60 sec, ISO800. See if you can spot any fluctuations in exposure:

 
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A quick zoom test of the Panasonic 14-45mm f3.5-5.6 lens in manual focus mode on the Panasonic G2, with exposure set to f5.6, 1/60 sec, ISO800. See if you can spot any fluctuations in exposure:

 
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A quick zoom test of the Panasonic 45-200mm f4-5.6 lens in manual focus mode on the Panasonic G2, with exposure set to f5.6, 1/60 sec, ISO800. See if you can spot any fluctuations in exposure:

 
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A quick zoom test of the Olympus 50-200mm f2.8-3.5 non-SWD lens in manual focus mode on the Panasonic G2, with exposure set to f3.5, 1/60 sec, ISO800. See if you can spot any fluctuations in exposure:

 
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I've been planning on selling some of my lenses on Ebay and these tests have helped confirm which ones to keep:

Olympus 35-100mm f2.0 - impeccable image quality with marvelous wide-open speed
Panasonic 14-50mm f2.8-3.5 - widest aperture available with rock-steady OIS
Panasonic 45-200mm f4-5.6 - compact telephoto with OIS and continous auto-focus
 
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