Aputre ISO and infintiy focus all controling focus?

Discussion in 'Photography Beginners' Forum' started by Hair Bear, Sep 24, 2006.

  1. Hair Bear

    Hair Bear TPF Noob!

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    Can confirm a point about Apature size and Depth of field

    A large Apature number = smaller apature and a large or long depth of field?

    This means on my lens if the max setting is 22 I will get max depth of field on that shot.

    So if that is correct, do I need to worry about focusing when using this apature size?

    If I set 22 on the lens and infinity focus will I get it all in sharp focus?

    If I set 3.5 on the lens the depth of field will be much smaller or shallow and therefore the focus point is critical?
     
  2. Alex_B

    Alex_B No longer a newbie, moving up!

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    true: a large aperture number/stop means a small opening and therefore large depth of field.

    false: maximum aperture stop means everything is in focus automatically.
    This really depends on what scene you try to capture. you don't really get an infinite depth of field.

    also sharpness is limited if you go to too large aperture stops as diffraction ruins your sharpness. with an aperture stop around 8 you never have to worry about diffraction, if you go to 22 you will.
     
  3. Hair Bear

    Hair Bear TPF Noob!

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  4. Alex_B

    Alex_B No longer a newbie, moving up!

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    depth of field is greatest on f/45, just you cannot see it since this is not a shot that requires large depth of field.
    what you can see is the effect of diffraction for larger numbers which kills your resolution.
     
  5. Hair Bear

    Hair Bear TPF Noob!

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    OK, can't wait to get my hands on aDSLR and then I can play with all these settings and see the results before I forget what I had done!!
     
  6. Alex_B

    Alex_B No longer a newbie, moving up!

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    Using larger apertures can be fun, play a bit with them as limited depth of field can add a lot of value to some images.

    BTW, small apertures will also nicely focus the dirt and dust on your camera's sensor ;)
     

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