HELP! Video and exposure even when on Manual

[Ian]

I am investigating a complaint that Olympus cameras change the exposure when zooming even when the exposure is set to Manual If this does indeed happen, I have a theory that could explain it. I'll reveal this later but in the mean time here are two short clips - can you detect any changes in exposure for each one?

Video A:

[ame="http://www.youtube.com/watch?v=zVDKM3WDB_E"]P7160414 - YouTube[/ame]


and


Video B:

[ame="http://www.youtube.com/watch?v=0FPaY48Ob64"]P7160412 - YouTube[/ame]

What do you think (and please excuse the bad focus on one of the clips, which is not related to this investigation).

Ian

[pvasc]

Re: Video and exposure even when on Manual

Wouldn't the exposure change because the area that is being meter changes? I know when I do crops in Lightroom the histogram changes.

[Ian]

Re: Video and exposure even when on Manual

Wouldn't the exposure change because the area that is being meter changes? I know when I do crops in Lightroom the histogram changes.

Manual exposure was used so in theory the exposure of any given area of the frame should remain constant.

Ian

[Imageryone]

Re: Video and exposure even when on Manual

Certainly appears to be a more noticeable difference in the first video than the 2nd, bvut, not being a videographer , no idea why

[Ian]

Re: Video and exposure even when on Manual

Certainly appears to be a more noticeable difference in the first video than the 2nd, bvut, not being a videographer , no idea why

Your answer is interesting - and why? I will reveal later!

Anyone else?

Ian

[Graham_of_Rainham]

Re: Video and exposure even when on Manual

If the maximum aperture zoomed in is f/6.3 then any aperture set wider than this at wide angle is reduced on zooming in. With the video "shutter" speed effectively consistent depending on frame rate, would this account for any difference. Assuming Auto ISO is not active.

Is AWB active in video mode

As I almost never shoot video, this is pure guess work

[Magnusrn]

Re: Video and exposure even when on Manual

While I realise this is a bit old, I noticed you hadn't provided the answer, this baffled me for a while, I only figured it out once I ended up with a camera that couldn't change aperture in live view(d7000)

Well it turns out that even though the tokina 11-16 is a CONSTANT f/2.8, the brightness adjusts when you zoom, because the aperture changes in size as you zoom, and cameras are made to adjust for it, and as the d7000 couldn't, it brightened.

While you see the flickering more in video A, although I'm not sure if it's apparent in B, maybe it's just the wb changing or something, the reason for it is that the first video has a variable aperture, and as you zoom the camera adjusts to compensate, even though you could be shooting at f/11.