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Thread: Under-Exposure Issue

  1. #1
    bisso7's Avatar
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    Jeff

    Under-Exposure Issue

    For those of you who do not know, I am very much a beginner, and I am asking for some feedback about this situation. I have no clue as to what I did incorrectly, but I ended up with a dark blob for an exposure. I'm only posting the photo so you can see for yourself.

    I was shooting (Canon Rebel T3) a small creek of running water at very close range, using the kit lens and had my camera mode on "Tv" (Shutter Priority). My intention was to get a crisp, clear exposure of the running water, which is why I chose the high shutter speed.

    When I pressed the shutter release halfway, my apeture setting (5.6) was blinking, but I didn't know how to correct the problem. Settings were as follows: f/5.6, 1/1600, ISO: 400, 55mm at close range. I was under a bridge, in a shaded area.

    Under-Exposure Issue

  2. #2
    Moderator GrumpyDiver's Avatar
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    Manfred Mueller

    Re: Under-Exposure Issue

    The blinking aperture reading was indicating that based on your ISO setting and selected shutter speed, you would not be able to get a correct exposure. I would assume that the maximum aperture on that particular len / zoom setting was f/5.6.

    You will have to increase your ISO setting, decrease your shutter speed or both. Using flash to get more light into the image would work too, but I suspect that the reflection is not something you would want in the image.

  3. #3
    bisso7's Avatar
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    Re: Under-Exposure Issue

    Thanks for the comments, Manfred....Well, I tried raising the flash and still got the flashing aperture setting, so I didn't use the flash. I did try decreasing the shutter speed, though not by much, and the aperture setting was still flashing. I really don't know enough, yet, to "really" know what I'm doing. LOL Everything is so experimental at this point.

  4. #4
    Moderator GrumpyDiver's Avatar
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    Manfred Mueller

    Re: Under-Exposure Issue

    Remember that you have three variables that can be adjusted for a given lighting situation; ISO, aperture and shutter speed. If you fix two of these variables; in your case ISO 400 and shutter speed at 1/1600, you have to have a aperture setting that allows enough light in to correctly expose the image. In shutter priority mode, you tell the camera which shutter speed to use, and it tries to select an aperture that gives you the correct exposure. If the camera can't do so, it warns you, but takes the picture anyways.

    Personally, I think the 1/1600 is way too fast to get realistic looking water, so backing that down to something more reasonable (I tend to shoot water slowly so that you can see the flow), you should have a situation where there is enough light for the exposure. If it still does not work, increasing ISO speed will increase the light sensitivity of the exposure and move in the right direction. The only downside of increasing ISO speed is that you will eventually start seeing digital noise in the image and your dynamic range will drop.

  5. #5

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    Re: Under-Exposure Issue

    Hi Jeff,

    I'd suggest a good starting point is to put the camera into Av mode, and get a feel for the kinds of shutter speeds that you're going to need to use to get a good exposure at various ISO settings.

    The basic issue you're having here is one of massive under-exposure: at your selected ISO and shutterspeed the aperture ("hole") in the lens can't get big enough to let enough light in in the required time.

  6. #6

    Re: Under-Exposure Issue

    Quote Originally Posted by bisso7 View Post
    I did try decreasing the shutter speed, though not by much, and the aperture setting was still flashing. I really don't know enough, yet, to "really" know what I'm doing. LOL Everything is so experimental at this point.
    Digital photos are free (you don't waste any money if you take a shot that doesn't work out) so feel free to experiment. Take a shot (it's bad) change one setting and take another - is it better or worse? Change the same setting again and take another, and another. Seeing what the changes you make do is a great way to learn and with digital it is easy to experiment because you aren't burning up rolls of film.

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