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Thread: CloseUp and Focussing distance

  1. #1

    Default CloseUp and Focussing distance

    HI All,

    Want to confirm on this:

    If my lens minimum focussing distance is 0.5m and I use a +4 CloseUp filter, will my focussing distance be 0.5/4=12.5cm???? Or it's 1/4=25cm??

    Thanx
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  2. #2
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    should be 25 cm.

  3. #3
    Member patch17's Avatar
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    Quote Originally Posted by mpenza
    should be 25 cm.
    huh? I thought the filter will shorten the min focusing distance by 4, i.e. to 12.5 cm.

    if it's 25 cm, that means if it's a +2 filter, min distance remains at 0.5m (1/2 = 0.5).
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  4. #4

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    Quote Originally Posted by patch17
    if it's 25 cm, that means if it's a +2 filter, min distance remains at 0.5m (1/2 = 0.5).
    Any focal length, be it a 20mm or 500mm, will focus at 25cm (minimum) when you added +4 closeup filter into it. You're right if +2 filter is added, the min focusing distance will still remain at 0.5m, but magnification wise we have to test.

  5. #5

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    Quote Originally Posted by Sgt. Pepper
    Any focal length, be it a 20mm or 500mm, will focus at 25cm (minimum) when you added +4 closeup filter into it. You're right if +2 filter is added, the min focusing distance will still remain at 0.5m, but magnification wise we have to test.
    you mean using a +4 filter, you don't enable macro mode and shoot?
    What's the difference with using a macro mode and the filter? the c730 has super macro mode, so do I still need a close up? Practically speaking, what do i actually do with it? thanks!
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  6. #6

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    Quote Originally Posted by KSeet
    you mean using a +4 filter, you don't enable macro mode and shoot? What's the difference with using a macro mode and the filter? the c730 has super macro mode, so do I still need a close up? Practically speaking, what do i actually do with it? thanks!
    You dont have to enable macro mode if you'll going to attach +4 filter, it's because +4 can already give you a much closer focusing distance. If you think that the magnification of your C730 is enough for the size of the subject you're shooting, I suggest that you dont attach any closeup filter as it may only degrade the quality.

  7. #7
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    Quote Originally Posted by Sgt. Pepper
    Any focal length, be it a 20mm or 500mm, will focus at 25cm (minimum) when you added +4 closeup filter into it. You're right if +2 filter is added, the min focusing distance will still remain at 0.5m, but magnification wise we have to test.
    hmmm.... an interesting feature.

    that means if my lens' min focus distance is 1m, by adding a +4 it goes down to 25cm. But what would happen if the min focus distance is less than 25cm?
    (say a zoom with 1:4 macro feature. I think it can focus to less than 25cm.)

    worth an experiment...
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    No, I think regardless of whats your lens min focus distance is, the focus distance when added with a +4 close up filter is always around 25cm. Anyone correct me if I am wrong..
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  9. #9

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    Quote Originally Posted by patch17
    hmmm.... an interesting feature.

    that means if my lens' min focus distance is 1m, by adding a +4 it goes down to 25cm. But what would happen if the min focus distance is less than 25cm?
    (say a zoom with 1:4 macro feature. I think it can focus to less than 25cm.)

    worth an experiment...
    It's the same case as using extension tube and closeup filter combination for macro. From one of the threads here I mentioned that there might be a conflict there, since extension tubes are meant to get a closer focusing distance that might be closer than the close up filter can give. But, I doubt whether you can ‘override’ the min focusing distance of the closeup filter. It’s worth a try.

    Keep in mind that the minimum focusing distance is not the only factor to gain magnification. A lens that can focus at a min of 25cm at wide open may have lesser magnification than the lens that can focus at a min of 50cm at full zoom.

  10. #10

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    Quote Originally Posted by patch17
    hmmm.... an interesting feature.

    that means if my lens' min focus distance is 1m, by adding a +4 it goes down to 25cm. But what would happen if the min focus distance is less than 25cm?
    (say a zoom with 1:4 macro feature. I think it can focus to less than 25cm.)

    worth an experiment...
    if the min focus distance is less than 25cm , adding a closeup filter +4 serve no purpose. A closeup filter +4 will work well for longer focal length like 200mm.
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    Quote Originally Posted by megaweb
    if the min focus distance is less than 25cm , adding a closeup filter +4 serve no purpose. A closeup filter +4 will work well for longer focal length like 200mm.
    ah... so a close up filter basically works like a magnifying glass. e.g. the lens is our eye and the filter is the glass. There's a minimum distance you have to set the glass to get a clear, magnified view of the object, and it doesn't matter how far we set our eyes away from the glass, the object is only magnified so much as the glass allows.

    hmmm... another experiment to try at home, attaching a magnifying glass to the end of the lens.
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    Quote Originally Posted by patch17
    hmmm... another experiment to try at home, attaching a magnifying glass to the end of the lens.
    no need to try, confirm already, a simple close-up filter is basically the same as a magnifying glass, only that it's convex on one side, not both.

    reading glasses that your parents/grandparents may use are similar to close-up filters too, so basically a +4 close up is the same as a 400 degrees long-sighted spectacle lens (i think).

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