E-P1 darkens while zooming during videos

barronchung

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Hi there, I'm new to the forum, and couldn't find any other threads on this. I have the 14-42mm zoom lens and was wondering if anyone else noticed that the video darkens when you zoom in while recording? I know the lens' maximum aperture changes as you zoom, but I would have thought the camera could compensate for that by adjusting the shutter speed or gain? I tried using aperture priority in video mode and setting it at f5.6 so that the aperture would stay constant, but that didn't seem to keep the exposure constant either. Does anyone else have this problem or is it just me? Thanks.
 

deirdre

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My first question: is the area you're zooming into darker than the average part of the wider frame?
 

barronchung

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Here's a sample:
[ame="https://www.youtube.com/watch?v=cYANzf7_UA8"]https://www.youtube.com/watch?v=cYANzf7_UA8[/ame]
 

icase81

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Could be because you have the aperture wide open. When you zoom, that max aperture gets smaller.
 

Brianetta

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Could be because you have the aperture wide open. When you zoom, that max aperture gets smaller.
barronchung is using aperture priority mode, where the diaphragm opens and closes to maintain the correct ratio even when zooming. I've just tried this, and as I zoom in to a blank patch of wall, I can see the brightness darkening, then increasing in jumps, along with the sound of the diaphragm's aperture changing.

All zoom levels are capable of f/5.6 on that lens.
 

barronchung

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Sorry that video clip was tested in program mode, let me try again in aperture mode @f5.6 when I get home...

Brianetta, do you get that while you are recording video or just pointing at stuff without recording? Mine brightens/darkens itself when I'm not recording, but it's while recording that I notice it doesn't auto-compensate.
 

Brianetta

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barronchung, I just tested it. You're absolutely right, the aperture isn't adjusted when zooming whilst recording. The image just gets darker. The camera does appear to adjust the exposure some other way, though - presumably by altering the ISO (or sensor gain; not sure if ISO is the correct term for movie mode). It's slow, in any case, gradually getting brighter after zooming in, then darkening after zooming out.
 

barronchung

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OK thanks, at least I'm not the only one!

I guess I didn't wait long enough to see it adjust the brightness, glad to know that it does eventually (even if slowly) do that. Anyways, thanks for testing it out on yours!
 

icase81

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barronchung is using aperture priority mode, where the diaphragm opens and closes to maintain the correct ratio even when zooming. I've just tried this, and as I zoom in to a blank patch of wall, I can see the brightness darkening, then increasing in jumps, along with the sound of the diaphragm's aperture changing.

All zoom levels are capable of f/5.6 on that lens.
I should learn to read better :)
 
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