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Thread: Changing Exposure During Totality

  1. #1
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    Changing Exposure During Totality

    All,

    I was shooting a video on my back-up camera as totality came and went on Monday using an old Rebel T2i. Unfortunately, the exposure continuously adapted to keep the lighting about the same. Is the exposure information embedded in the video file somehow? I'd like to know what the exposure was as a function of time in the video.

    Thanks.

  2. #2
    Senior Member Jonathan Huyer's Avatar
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    I don't know about exposure information during videos, but I do think that some kind of exposure adjustment would be essential during the event. Otherwise you would probably go completely black during totality, due to the very wide difference in lighting. I was doing a time-lapse with a wide-angle lens, for the period of totality +/- about 5 minutes on either side. I set the camera to Av mode, ISO 800 at f/5.0. At the start the shutter speed was 1/3200 sec, and during totality it was 1/15 sec. Once I finish processing it, I'll put it together and post a link.

  3. #3
    Super Moderator Kayaker72's Avatar
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    Quote Originally Posted by Jonathan Huyer View Post
    Otherwise you would probably go completely black during totality, due to the very wide difference in lighting.
    I had video going on my G7x mounted on a gorillapod. I started it a few minutes before totality: 1/250, f/5 and ISO 400. In M mode (nothing auto). That was 1 stop above proper exposure with ~95% of the sun covered.

    Scene went pitch black during totality except for a sliver along the horizon.

  4. #4
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    We had clouds off in the distance that were outside of totality (still in the penumbra though). They were pretty bright. The street lights came on where I was so I really couldn't say how dark it was. But the sky was blue, not black.

  5. #5
    Senior Member Jonathan Huyer's Avatar
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    Here is my completed time-lapse. It covers about 14 minutes at 10x normal speed. I brightened the foreground in Lightroom equally for each frame.

    https://photos.smugmug.com/photos/i-...Spb9n-1280.mp4

  6. #6
    Super Moderator Kayaker72's Avatar
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    I just played around with some numbers. But a typical bright day is 18 EV. About 3 minutes before totality, I started my video and set it at 1/250th, f/8, ISO 400, or about 12 EV. That was about +1 EV, so the scene was ~11 EV with 180 seconds to go. During totality, my M3 had trouble focusing. I missed a couple of shots. It's lower range is rated at EV 2. So, best guess, totality was ~EV 1-3. So, we went from EV 18 to EV 1-3, or dropped 15-17 stops of light, with 8-10 of those stops coming in 180 seconds. This fits with a chart I just found for different EVs that listed EV 2 as "total eclipse of the moon."

    BTW, my G7x II, which I had mounted on a gorillapod, also lost focus. It went blurring during totality.
    Last edited by Kayaker72; 08-27-2017 at 09:27 PM.

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