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Thread: how closeup filters affect focal distance?

  1. #1
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    Default how closeup filters affect focal distance?

    anyone can help regarding the hoya +4? how does it change the min distance? is it like the 500D where the range hovers around a fixed value? or it just magnifies the image?
    "I'm... dreaming... of a wide... angle~
    Just like the ones I used to know~"

  2. #2

    Default Re: how closeup filters affect focal distance?

    Originally posted by denizenx
    anyone can help regarding the hoya +4? how does it change the min distance? is it like the 500D where the range hovers around a fixed value? or it just magnifies the image?
    Yes, a close-up filter shortens the focusing distance to around a fixed distance. Of course, different diopter rating gives different distance. Just divide 1m by the diopter value and you'll get the focusing distance. E.g, A +1 filter will focus at 1m, a +4 filter will focus at 25cm, etc.

    A 500D does so similarly too.

    By reducing the focusing distance, logically the object is being magnified.

  3. #3

    Default Re: how closeup filters affect focal distance?

    Originally posted by denizenx
    anyone can help regarding the hoya +4? how does it change the min distance? is it like the 500D where the range hovers around a fixed value? or it just magnifies the image?
    Ur focus is ard 25cm i think
    http://kkeys.home.texas.net/science/photo/macro.html

  4. #4
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    that's cool huh? regardless of lens?
    "I'm... dreaming... of a wide... angle~
    Just like the ones I used to know~"

  5. #5
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    Default

    sorry again... so I can focus on 25cm and below or above? above right? but no infinity.
    "I'm... dreaming... of a wide... angle~
    Just like the ones I used to know~"

  6. #6

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    Originally posted by denizenx
    sorry again... so I can focus on 25cm and below or above? above right? but no infinity.
    ard 25cm. Other than that blur. But very hard to estimate, usually i move the cam in until the insect becomes focussed. The higher the +, the closer u can move in but the easier for u to get OOF.

  7. #7
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    wah... ok thx! i'll go n buy it then
    "I'm... dreaming... of a wide... angle~
    Just like the ones I used to know~"

  8. #8
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    aiyah I'm a bum...
    been shooting food rencently, using my 19mm.. so +4 need to get 77mm also..
    OR is an extension tube better?
    alamak so fickle from ignorance...
    "I'm... dreaming... of a wide... angle~
    Just like the ones I used to know~"

  9. #9
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    Default

    Originally posted by denizenx
    aiyah I'm a bum...
    been shooting food rencently, using my 19mm.. so +4 need to get 77mm also..
    OR is an extension tube better?
    alamak so fickle from ignorance...
    hmm....may be extension tube better??? i GUESS closeup filter are more suitable for DC user who can't take out the lens like SLR

    somemore for extension tube, no glass is added and it can also use for ANY of your lens....not only 77mm one...and it is cheaper...less than $100 for a 3rd party one..

    but usage and quality wise...i never try before...may be our insect king can tell us more??
    We are HDD of PC & FT are MB add to storage;
    so PC never hangs with enormous storage capacity - LKY

  10. #10

    Default

    Originally posted by denizenx
    aiyah I'm a bum...
    been shooting food rencently, using my 19mm.. so +4 need to get 77mm also..
    OR is an extension tube better?
    alamak so fickle from ignorance...
    Wah, u need to see microorganisms on your food is it?

  11. #11
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    oh insect king insect king!
    LOL I only UST found out that AH is really alex hosp... where's the gdn? I stay there before...
    "I'm... dreaming... of a wide... angle~
    Just like the ones I used to know~"

  12. #12

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    Saying that using a +4 will focus at 25cm is inaccurate. The camera will focus at 25cm if you set your lens is focus at infinity. If you set your lens focus to less than infinity, then the actual focal point will be less than 25cm.

    Using a +4 close-up lens changes the possible focusing distance from

    a (where a is lens min focusing distance) to infinity

    to

    b to 0.25m

    where b is

    0.25a / (0.25 + a)
    Last edited by reflecx; 26th November 2002 at 06:29 PM.

  13. #13

    Default

    Originally posted by reflecx
    Saying that using a +4 will focus at 25cm is inaccurate. The camera will focus at 25cm if you set your lens is focus at infinity. If you set your lens focus to less than infinity, then the actual focal point will be less than 25cm.

    Using a +4 close-up lens changes the possible focusing distance from

    a (where a is lens min focusing distance) to infinity

    to

    b to 0.25m

    where y is

    0.25a / (0.25 + a)
    Wow, where did u get that formula from? I only read about the 25cm at infinity rule from web pages.

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