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  1. #1
    Loose Gravel's Avatar
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    Close-up filters: how close?

    I'm considering adding 'close-up filters' to my Pentax 67 system. I'm unclear how much closer I'll be able to get for a given lens with +1, +2, or +3 diopters. Anybody know how to do this calculation?

    Thank you. --LG--
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    Ole
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    With any lens focussed at infinity, a +1 will give focus at 1 meter from the filter. A +2 at 1/2 meter, and a +3 at 1/3 meter.

    This far it's easy. What happens when the lens is focussed at something other than infinity is a bit more complex.
    -- Ole Tjugen, Luddite Elitist
    Norway

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    I have a P67 and a Pentax 2 element close up lens (can't remember which one offhand) so could measure actual distances/size of ruler in viewfinder if that would be useful. 105, 135, 165, 200?

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    How do you calculate this for closer focusing? (in other words 1:1 or closer)

    I use these diopters on my 120mm LF macro lens. With enough bellows draw for 2:1 magnification, by stacking +1, +2, and +4 filters, I get 6:1 or 7:1 magnification and I can focus an inch away from the subject.
    Paul

  5. #5
    Loose Gravel's Avatar
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    Quote Originally Posted by MartinB View Post
    I have a P67 and a Pentax 2 element close up lens (can't remember which one offhand) so could measure actual distances/size of ruler in viewfinder if that would be useful. 105, 135, 165, 200?
    MartinB, I'd be interested to know for the 135 Macro. Thanks.

    --LG--
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  7. #7

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    Pentax T132

    Quote Originally Posted by Loose Gravel View Post
    MartinB, I'd be interested to know for the 135 Macro. Thanks.

    --LG--
    LG,

    I checked with my Pentax T132 as well as a set of lesser quality 67mm Vivitar diopters that are hanging around. The Pentax close up lens is much higher quality as it has 2 glass elements and I no longer use the Vivitars. I have tubes if I need to get closer. According to the page on Max's link, the Pentax is a +.76 diopter. The Vivitar's are +1, +2 and +4.

    With the 135mm macro at its closest focusing distance I measured the distance the from the target to the approximate film plane (I used the serial number on the left top plate as a proxy) Without a close up filter, the 135mm macro can get no closer than 30". Without changing focus on the lens, each higher powered diopter allows the camera to move closer to the target and thus increase the magnification.

    I put a ruler on the target and looking through the viewfinder, measured the max length of the long side. An object of that length will fill the frame from side to side. I used the waist level finder since the pentaprism did not see the whole frame. For instance, 16 cm seen using the waist level finder was only 14 cm using the pentaprism.

    The second column below is the closest you can get to the target and the last column is the length of the long side of the frame. Intestingly, it looks like you need +4 to get 1:1 magnification using closeup diopters on the Pentax 67 135mm macro lens.

    -----------target to film plane-----------length of long side

    no filter------[ 30"......76cm ]------------[ 8 1/2".....22cm]

    T132---------[ 24"......61cm ]------------[ 6 1/4".....16cm ]

    +1-----------[ 22"......56.5cm ]-----------[ 5 1/2".....14cm ]
    +2-----------[ 18.5" ...47cm ]-------------[ 4"..........10.5cm ]
    +4-----------[ 15"......38.5cm ]------------[ 2 3/4".....7 cm ]

    Martin

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    Loose Gravel's Avatar
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    Thanks, that's good info. --LG--
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    Avoid the one element lenses like the plague. They're uniform, as in terrible.

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    Pentax 67 Instruction Manual on their CLOSE UP Lenses

    http://www.pentaximaging.com/files/m...-Up_Lenses.pdf

    Dan
    www.antiquecameras.net

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