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Thread: 4X28 Binocular Versus a 200mm f1.8

  1. #1

    Default 4X28 Binocular Versus a 200mm f1.8

    I wondering who will win if the task is to see a very small newspaper fine print in very dark condition. I am very curious why there is no equivalent of exit pupil in DSLR. Let say the DSLR body is a 500D and the image can be viewed 100% on the computer. The print become smaller and smaller till one optics equipment cannot see the words I think one unfair advantage DSLR has is that it can ram up its ISO
    Last edited by maisatomai; 1st September 2009 at 08:52 PM.

  2. #2

    Default Re: 4X28 Binocular Versus a 200mm f1.8

    Smaller print has NOTHING to do with ISO. I don't see how you even can make a connection.

    Get a lens and camera body with a high resolution (like Sony A900 with a CZ 135mm) and then put it on a tripod, ISO 200, and then just use long exposure. Unless it's totally dark, you should be able to read the print unless the print is too tiny to be resolved.

  3. #3

    Default Re: 4X28 Binocular Versus a 200mm f1.8

    Sorry.... The example I have given is purely academical. My point is why there is no comparison between exit pupil and f-stop. The higher the exit pupil, the less light is needed. The smaller the f-stop for a certain lens, the less light is needed. For example, a 7mm exit pupil is equivalent to f1.2???

  4. #4

    Default Re: 4X28 Binocular Versus a 200mm f1.8

    Depends on the binocular too though.

    But an exit pupil of 7mm is the same as the maximum size of the human pupil, thus you could argue that it's f/1.0? But it doesn't translate into how much light is actually let through in terms of f-stops. An 8x56 should capture more light than a 4x28, but then your own pupil will adjust to compensate if too much light is let through.

    Plus how old are you? The maximum your pupil can expand to (unless fully dark-adapted) decreases with age. So the amount of light from the binocular (without filters) is regulated by your own pupil, thus your pupil is essentially the aperture for an f/1.0 (7mm pupil diameter) lens.

    If you're 40, the most the average human pupil can dilate to is 6mm. Thus it would look like an f/1.16 or f/1.2 aperture lens, etc etc.

  5. #5

    Default Re: 4X28 Binocular Versus a 200mm f1.8

    That mean a 200mm f5.6 will be totally useless in dark condition since it will be like a 4X4 binocular (I don't know the Math behind it but I guessing from Rashkae's post).


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