oly zuiko 14-54mm gets darker zooming in

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psoetio

Member
Testing my new lens using fully manual exposure, when I zoom in at a fixed f-stop the picture gets darker! One test I did was with an evenly lit gray carpet with a white piece of paper in the middle of the shot. I metered for correct exposure at max wide angle and set the aperture at f8. Then zooming in so the paper filled more of the screen, you would think that the exposure meter would start to indicate overexposure, but actually it goes the other way and the picture is clearly getting darker. With no paper in the center the meter shows even more underexposure as I zoom in. Then, if I open up the aperture to correct the exposure, it jumps to being slightly overexposed, and if I then go back to the original f stop it is correctly exposed! Is there something I'm doing wrong? Using the Panasonic adapter for m43 to 4/3. Please help!

I'm using it on a GH2
 
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I don't think the Oly lens you indicated is a constant aperture.
Try it with a constant aperture lens.
 
video not pics

video not pics

When I play back the video I still see the same lightening and darkening. This lens is not a constant aperture in the sense of being able to stay at f2.8 throughout the zoom range, but my test was with a manual aperture setting of f8, so shouldn't it stay at that setting? The camera indicates that it is still at f8 as I zoom in, but the picture gets darker. The weirdest thing is how when I go up a third of a stop and then back down to the original f8, the picture is brighter! I'm just wondering if there is some setting on the gh2 for when a 4/3 lens is being used.
 
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