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Exposure changes when zooming even in fully manual

Discussion in 'Videography' started by harrisdpi, Apr 21, 2017 at 12:43 AM.

  1. harrisdpi

    harrisdpi New Member

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    Has anyone else noticed that the image exposure changes when zooming in or out while filming, even though ISO, aperture, shutter speed and white balance have been locked down?

    If so, is there a way around it?

    When I get a chance I will post an example.
     
  2. Gaston

    Gaston Premium Member

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    Normal if your lens doesn't have a fixed aperture... like the 18-55 or the 55-200 for example...
     
  3. Goldingd

    Goldingd Premium Member

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    First answer, well actually a question first, is what particular zoom lens? If is one with a variable aperture, then that is fully expected.

    Second answer, if it is a fixed aperture (aka constant aperture) zoom lens, then that depends upon the quality of the optic design.

    Note, I am not talking about depth of field.

    Incidentally, focus can change as well (depending on quality of optic design)
     
    Last edited: Apr 21, 2017 at 2:03 AM
  4. SausalitoDog

    SausalitoDog Premium Member

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    Depends on the lens. Many of the fuji zooms change aperture as they zoom.
     
  5. Shadowside

    Shadowside Good Glass is Forever...

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    In addition to the valid points already mentioned...

    Even if the lens has a fixed aperture your metering method will be affected by a change in content, for example if using average or matrix as the content changes so will the average EV, if using spot this can also happen as you zoom in your meter is less influenced by surrounding luminance.

    If you want to test the variance for this with you meter you will need an even (large) light source and a large consistent surface (wall),. focus at infinity (manually) and be within a meter of the wall (or so). Do your test with a high enough ISO setting to allow for hand held speed (meters are less accurate at either extreme end of their range) and stop down one stop to reduce the effect of vignetting changing at different focal lengths.

    When you are all done this test, read an article on the ISO-Less sensor like those used in Fujis. :)

    ISOless Photography With the Fujifilm X-Series

    :)
     
  6. starlights

    starlights Premium Member

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    Is your observation based on reviewing actual footage or just what you noticed through EVF while filming? What mode is your EVF set to? Is it possible that its only the EVF compensating ? Try setting it to the non-studio mode (I am forgetting what is it called in the camera menu)...

    If, as stated, your aperture, SS and ISO is locked down, then the only reason your exposure will change while zooming "out" with a variable aperture zoom such as 18-55 or 55-200 is if your aperture is locked down at the widest and you were zoomed in to a focal length where the available aperture was smaller than the value locked down. In this case while zooming out the camera will try to set it to the widest aperture that is locked down and now becoming available as your zoom out. Lock your aperture value to one of the constantly available apertures and you should not see this phenomenon.
     
    Last edited: Apr 21, 2017 at 4:37 AM
  7. starlights

    starlights Premium Member

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    The metering should not affect the exposure if the aperture, SS and ISO are all locked... should it? Otherwise what would be the point of using all manual while filming? Unless I misunderstood and you were referring to how EVF handles it, not the actual recording

     
  8. Shadowside

    Shadowside Good Glass is Forever...

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    Correct, it shouldn't affect the exposure if the camera is on all manual. However, if you are testing the meter of the camera (as I wrongly assumed was the OP's point here) there are many things that will affect the meter that are not as 'fixed' as we think they are. :)

    Sorry to distract, I will go back to hockey and my scotch lol...
     

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