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  1. #1

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    Close work with a Bronica SQ-A

    I've got a Bronica SQ-A and an 80mm f/2.8. I have no problem with the lens except the distance I must maintain from my subject. Now I'm not looking to do true macro work, just get a little closer to my subject than I can now.

    I really have got it down to 2 options: 110mm f/4.5 or get an 18mm extension tube and use my 80 f/2.8. I'm wondering what the effective f/ would be if I got the 18mm extension tube? If it's around 4.5, and there are no other sirious issues in terms of quality when using an extension tube, then I'll probably go with that just to reduce cost.

    Any opinion is welcome and appreciated

    Thanks!

    Joe

  2. #2

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    18 mm with an 80 mm lens would reduce the maximum f-stop of 2.8 to an effective one of 3.5 (i.e. about 0.5 stop less) with the lens itself set to infinity.

    You will want the 18 mm to add to the extension built-in to the focussing mount, so the lens will be set to the close focus limit (what's that, 0.9 m/3 ft?).
    Then the reduction is about 0.7 - 0.8 stops, turning f/2.8 into an effective f-stop of just a bit wider than f/4 (at an image scale of about 1:3).

  3. #3

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    Thank you very much, this has made my decision rather clear. do you know what the 18mm extension tube between the lens and the body would do for image scale?

    Joe

  4. #4

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    Quote Originally Posted by Joe O'Brien View Post
    Thank you very much, this has made my decision rather clear. do you know what the 18mm extension tube between the lens and the body would do for image scale?

    Joe
    I'm assuming the lens focal length is indeed 80 mm, not 81.6 or something like that (which it usually is - never the exactt nominal focal length).

    With the lens set to infinity, 18 mm of extension added, the scale is about 1:4.4, i.e. the smallest field of view will be about 25 cm square.

    To calculate the scale and field of view with the lens set to the cose focus limit, i would need to know the minimum focussing distance. Which i don't.
    So i'll assume (as i have done earlier) that it is about 90 cm/3 ft, i.e. an extension of just short of 9 mm.
    Then, with the extra 18 mm, the scale will be about 1:3, the minimum field of view about 17 cm square.


    By the way: assuming that minimum focussing distance of about 90 cm, the scale will be about 1:9 , the minimum field of view about 51.4 cm square.
    So there is a leap from a field of view of about 51 cm to one of about 25 cm when adding the 18 mm tube. A gap you could bridge by using a tube of 9 mm length (if there is such a thing for the SQ-A).

  5. #5

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    Okay, the actual minimum focusing distance is 80 cm, but I do get the idea from what you've told me. Thank you for the information, I was just hoping that I would be able to focus close enough and have a wide enough aperature for this to make more sense than the 110 f/4.5.

    Thanks

  6. #6

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    Given that 80 cm, with extra 18 mm, the scale will be about 1:2.8, the minimum field of view about 16 cm square.
    (Without those extra 18 mm, scale 1:7.9, field of view 44.5 cm.)

  7. #7

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    If it helps, the PS110mm lens focuses down to about 2 feet and gives a field of view of just over 8" across. Its a great lens. I find the "macro" lens more flexible tham tubes for the work I do, though its doubtless more expensive.

  8. #8
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    Quote Originally Posted by David Henderson View Post
    If it helps, the PS110mm lens focuses down to about 2 feet and gives a field of view of just over 8" across. Its a great lens. I find the "macro" lens more flexible tham tubes for the work I do, though its doubtless more expensive.
    I believe that's the 110mm f4 that goes down to a 1:4 -- yes? The 110 f4.5 goes down to 1:1, although supposedly at 14 inches, as though there are some internal tricks going on. I have the latter and it's pretty sweet. I got a steal on it via eBay, but they don't show up often, especially at under $300 in beautiful condition.

    It's odd that there are two PS 110mm, but hey, they didn't ask me!


  9. #9

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    I'd love to get my hands on a f/4.5. So I'll keep an eye out on ebay, but the only ones I've seen were at KEH for $650, pretty far outside of what I'd like to pay for something to get me up close. But hey, if I really get into this close up work I'm sure I'll get one eventually.

    Also, thats a great shot DWThomas!

    Joe

  10. #10
    NJS
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    105/3.5 S and 180/4.5 can be used for little bit of close up work too. 105 has a minimal focusing distance (MFD) of 0,8~m and 180 has MFD around 1m. I haven't tried 180PS, heard it is supposedly Schneider built lens, I have 105S and it's very nice lens wide open, very sharp and contrasty... I don't how close do you need to get, but here's something close to MFD of 105S:

    and this, wide open (1/30s):

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