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  1. #31
    Andy K's Avatar
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    Danilo, artistic element is not compulsory for showing an image. It is just as valid if you are showing it for technical reasons.


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  2. #32

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    Andy K: You are right, but am acting like any noob in any proffesion

    Maybe it is good idea to change aperture during the exposure, does anybody know something about it?

  3. #33
    Andy K's Avatar
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    I think if you changed aperture during the exposure you would probably get a blurred image. Because no matter how carefully you turn the aperture ring the camera will vibrate.


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  4. #34
    Lee L's Avatar
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    You can change aperture during a long exposure without visible camera shake if you cover the lens with a non-reflective black card (velvet or flocked paper would help) or a black plastic cup while you carefully adjust the aperture. You don't actually need to touch the lens with the card or cup, just block its field of view. Let the camera settle for a few seconds after you've touched it, then pull the card away. This does require a steady tripod mounting, but it works.

    There are lots of places to learn about reciprocity failure. Here's just one:
    http://home.earthlink.net/~kitathome...eciprocity.htm

    Lee

  5. #35

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    Quote Originally Posted by Danilo
    TBlocking lens is real smart idea, must try it. But how you exactly dodge?
    Let's say I want 5 minutes of ground plus 1 second of moon/sky. That should make for a pitch black sky plus a white moon without motion blur. I'd tape a small piece of black construction paper to the lens shade while looking through the viewfinder. Once all is set, I'd flip the mirror up and open the shutter with a cable release. At the end of the 5 minute exposure I'd block the whole lens with black construction paper in one hand, remove the paper from the lens cap with the other, then allow one more second of exposure before closing the shutter. I'll only make one exposure modification like this because I need the viewfinder to set up the paper.

    I'd recommend using a camera with depth of field preview to see just how sharp/blurry the cardboard is going to be at any given aperture. If you close down more than a couple of stops, the viewfinder will probably be too dark to see much during preview. You should, however, be able to judge what will happen if you watch the edge while operating the DOF switch slowly. The visibility of the paper edge will depend of the dimensions of the shade, aperture setting, focal distance, focal length, and lens construction. Experiment and see if it will work for you!
    Jacob

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