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Thread: How does aperture works?

  1. #1
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    Default How does aperture works?

    Okay this has been bothering me for quite sometime since I start to learn photography.

    As far as I know, the aperture's main function is to control the amount of light reaching the focal plane as well as the depth of field but why doesn't closing the aperture blades blocking up the image itself and resulting in a image when a black round border around it?
    Last edited by Scandiacus; 2nd September 2008 at 09:45 PM.

  2. #2

    Default Re: How does aperture works?

    the sensor doesn't capture what it sees in front but rather receive whatever comes onto it.

    think of it like this... comparing when you pour a pail of water thru a funnel with smaller opening above a tray and a funnel with a bigger opening at a similiar given time, the tray with the funnel having the bigger hole will collect more water. now if you understand this, then replace the water with amount of light, and the opening of the funnel with aperture opening.

    get it?
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    Default Re: How does aperture works?

    Quote Originally Posted by zzyzx View Post
    the sensor doesn't capture what it sees in front but rather receive whatever comes onto it.

    think of it like this... comparing when you pour a pail of water thru a funnel with smaller opening above a tray and a funnel with a bigger opening at a similiar given time, the tray with the funnel having the bigger hole will collect more water. now if you understand this, then replace the water with amount of light, and the opening of the funnel with aperture opening.

    get it?
    Sort of but, why don't the light from the object get all absorbed by the aperture blades when the hole's really small?

  4. #4

    Default Re: How does aperture works?

    the pupil of your eyes and the lens aperture work on the same principle.

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    Default Re: How does aperture works?

    Quote Originally Posted by attap seed View Post
    the pupil of your eyes and the lens aperture work on the same principle.
    I know, but, why won't we get tunnel vision when our pupil is really small in bright light, and same goes to a camera?

  6. #6

    Default Re: How does aperture works?

    Quote Originally Posted by Scandiacus View Post
    Okay this has been bothering me for quite sometime since I start to learn photography.

    As far as I know, the aperture's main function is to control the amount of light reaching the focal plane as well as the depth of field but why doesn't closing the aperture blades blocking up the image itself and resulting in a image when a black round border around it?
    did you get to play with pinhole camera last time in school?

  7. #7
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    Default Re: How does aperture works?

    Quote Originally Posted by night86mare View Post
    did you get to play with pinhole camera last time in school?
    Got but can't really remember liao.

  8. #8

    Default Re: How does aperture works?

    Quote Originally Posted by Scandiacus View Post
    Got but can't really remember liao.




    a camera is a camera.

  9. #9

    Default Re: How does aperture works?

    Light coming onto sensor is in all directions.

  10. #10

    Default Re: How does aperture works?

    Think of it as the iris in your pupil changing focus.

    The aperture blades do not close like your eye lids. That will be the lens "cover"

  11. #11
    Senior Member Override2Zion's Avatar
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    Default Re: How does aperture works?

    Quote Originally Posted by night86mare View Post




    a camera is a camera.
    Bro night86mare has the best answer. A picture speaks a thousand words. The smaller the opening (aperture), the least the diffusion and thus obtaining sharper image with maximal DOF.
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  12. #12

    Default Re: How does aperture works?

    Quote Originally Posted by Scandiacus View Post
    I know, but, why won't we get tunnel vision when our pupil is really small in bright light, and same goes to a camera?
    Do you get tunnel vision under bright sunlight? I don't.

    Anyway, it has to do with where the aperture diaphram is located.
    Last edited by lsisaxon; 3rd September 2008 at 09:47 AM.

  13. #13

    Default Re: How does aperture works?

    It is because you assume that everything in front of the lens (or at the middle of it) will leave its image on the sensor, which is not true.

    Only things those are near to the focused object will leave their images on the sensor. Things those are not with in the DOF will leave blur images. If you observe carefully, those blur images are half transparent.

    In extreme cases, there are some positions that any objects placed there will not leave the images on sensor at all. For example, right at the center of each lens. Draw something on your UV filter, then put it near the front element of your lens, then take picture, you will know what I mean.

    The apreture blades are placed at such a position, therefore, it can block the light as well as control aperture without leaving any image on sensor.

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    Default Re: How does aperture works?

    Ahh I see, I'm starting to get the picture (no pun intended), thanks guys


    Anyway, my curiosity sprouted when I saw this web page on custom made bokeh

    http://www.diyphotography.net/diy_create_your_own_bokeh

    The custom heart shaped aperture left me wondering why won't the image be blocked

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    Default Re: How does aperture works?

    Quote Originally Posted by Scandiacus View Post
    Okay this has been bothering me for quite sometime since I start to learn photography.

    As far as I know, the aperture's main function is to control the amount of light reaching the focal plane as well as the depth of field but why doesn't closing the aperture blades blocking up the image itself and resulting in a image when a black round border around it?
    The aperture is only an opening to allow light to reach the sensor/film. Light reaches the sensor through the aperture and for the sensor it can be said that the aperture is similar to a light source. Therefore, no black borders.

    Quote Originally Posted by Scandiacus View Post
    Ahh I see, I'm starting to get the picture (no pun intended), thanks guys


    Anyway, my curiosity sprouted when I saw this web page on custom made bokeh

    http://www.diyphotography.net/diy_create_your_own_bokeh

    The custom heart shaped aperture left me wondering why won't the image be blocked
    In this case, changing the shape of the aperture affects the image formed on the sensor. In the parts of the image that are in sharp focus, these aberrations are not noticeable but on the bokeh they are.

  16. #16

    Default Re: How does aperture works?

    Quote Originally Posted by Scandiacus View Post
    Ahh I see, I'm starting to get the picture (no pun intended), thanks guys


    Anyway, my curiosity sprouted when I saw this web page on custom made bokeh

    http://www.diyphotography.net/diy_create_your_own_bokeh

    The custom heart shaped aperture left me wondering why won't the image be blocked
    You can try but I'm quite sure the image will be blocked with wide angle lenses.

  17. #17
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    Default Re: How does aperture works?

    Quote Originally Posted by Override2Zion View Post
    Bro night86mare has the best answer. A picture speaks a thousand words. The smaller the opening (aperture), the least the diffusion and thus obtaining sharper image with maximal DOF.
    Diffusion?!

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