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  1. #31

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    Quote Originally Posted by AutumnJazz View Post
    Why is a fast lens hard to focus? (I haven't really used a RF before, but I understand how they work. Split image, right?)
    I have 3 fast M mount lenses (Nokton 35mm f1.2, Zeiss Planar 50mm f1.4, Zeiss Sonnar 50mm f1.5 ) and I don't find any of them hard to focus.
    Tom Hoskinson
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  2. #32
    AutumnJazz's Avatar
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    Basu's comment makes even less sense now.

  3. #33
    Anupam Basu's Avatar
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    I don't know how Tom's comment is relevant since he uses the Zeiss Ikon. That's what I use as well and I never claimed that a 35/1.4 would be hard to focus on that camera - it's a breeze to focus fast lenses with the ZI. Not so with the R4.

    The effective baselength of the Zeiss Ikon is almost 56mm - one of the longest EBLs around. The Bessa R4 is a meagre 19mm or so. Not even in the same ballpark. Focusing accuracy depends on the EBL. Longer the EBL, the easier fast lenses are to focus. So being able to focus a lens with a Zeiss Ikon has nothing whatsoever to do with the ease of focusing the same lens on an R4.

    -A

  4. #34
    AutumnJazz's Avatar
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    Uhhh...care to explain further?

  5. #35
    Anupam Basu's Avatar
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    Effective baselength = physical baselength x viewfinder magnification. It determines how accurately a rangefinder can focus. Think of it as an indicator of how much the split image in the RF moves per unit turn of the lens. Fast lenses need a longer EBL to focus accurately consistently because they have shallow DoF.

    EBLs of some of the common RFs (this is from memory and not exact, so do look them up to be sure)
    Leica M3: 62mm
    Leica M2/M4/M4-2/M4-P/M6/M6TTL (with the .72 VF) = 49mm
    Bessa T: 58mm
    Bessa R3x: 37mm
    Bessa R2x: 25mm
    Bessa R4x: 19mm
    Zeiss Ikon: 56mm
    Leica CL: 18mm
    CLE: 28mm

    As a rule of thumb, to judge whether a particular lens will be easily focusable with a given EBL, the entrance pupil size should be less than the EBL. So, for a 35/1.4 lens, what's the entrance pupil wide open? 35/1.4 = 25mm. So a rangefinder with an EBL of at least 25mm is required to focus a 35/1.4 lens accurately wide open with any consistency (remember this is a rule of thumb - someone can be extra cautious and get by with a relatively short EBL). For a 50/1 Noctilux, you'd need at least 50mm or so. So the M3, ZI or Bessa T and the M bodies would be okay. But Try focusing a Noctilux on a CL or an R4 and you'd have a very hard time and get inconsistent results. Thus, the fact that a lens focuses easily on the Zeiss Ikon, is of no relavance to whether it will focus well on an R4x.

    -A

  6. #36
    AutumnJazz's Avatar
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    So basically, I shouldn't get an R4A if I want a really wide and fast lens. :|

  7. #37
    Anupam Basu's Avatar
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    The R4 is a specialized wide angle camera which can also make do with 35 and 50mm lenses if required. You'd be ok with a 28/1.9 Ultron on it (28/1.9=14.73mm) but I would not choose it if I wanted to regularly use a 35/1.4 or a 50/1.5 on it wide open.

  8. #38

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    Quote Originally Posted by Anupam Basu View Post
    Effective baselength = physical baselength x viewfinder magnification. It determines how accurately a rangefinder can focus. Think of it as an indicator of how much the split image in the RF moves per unit turn of the lens. Fast lenses need a longer EBL to focus accurately consistently because they have shallow DoF.

    EBLs of some of the common RFs (this is from memory and not exact, so do look them up to be sure)
    Leica M3: 62mm
    Leica M2/M4/M4-2/M4-P/M6/M6TTL (with the .72 VF) = 49mm
    Bessa T: 58mm
    Bessa R3x: 37mm
    Bessa R2x: 25mm
    Bessa R4x: 19mm
    Zeiss Ikon: 56mm
    Leica CL: 18mm
    CLE: 28mm

    As a rule of thumb, to judge whether a particular lens will be easily focusable with a given EBL, the entrance pupil size should be less than the EBL. So, for a 35/1.4 lens, what's the entrance pupil wide open? 35/1.4 = 25mm. So a rangefinder with an EBL of at least 25mm is required to focus a 35/1.4 lens accurately wide open with any consistency (remember this is a rule of thumb - someone can be extra cautious and get by with a relatively short EBL). For a 50/1 Noctilux, you'd need at least 50mm or so. So the M3, ZI or Bessa T and the M bodies would be okay. But Try focusing a Noctilux on a CL or an R4 and you'd have a very hard time and get inconsistent results. Thus, the fact that a lens focuses easily on the Zeiss Ikon, is of no relavance to whether it will focus well on an R4x.

    -A
    Anupam is correct: the fact that a lens focuses easily on the Zeiss Ikon, is of no relevance to whether it will focus well on an R4x.

    Sorry about my logical lapse!

    I have a 2 Bessa T bodies and an R4M - haven't shot any film with the R4M since I got the Zeiss Ikon.

    I do shoot regularly with my Bessa Ts (1 body loaded with B&W and 1 with color).
    Tom Hoskinson
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  9. #39
    Anupam Basu's Avatar
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    Tom, isn't the Bessa T a wonderful camera? I have gone from a T to an M2 and eventually to a ZI now, but I still miss it - awesome RF as well. I'd like to try an R4 sometime, but I cannot justify a specialist wideangle body, especially since that money could go towards a lens. With the 15/28/50 combo on a ZI, I feel I have struck the right balance for my shooting.

  10. #40
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    I reviewed my friend's CV 35/1.4 here and bought my own a couple weeks later. I love the compact size of it and the extra speed comes in handy. I've had no problems focusing it wide open on an R2A. Like Basu, I also love the 28/1.9 Ultron (review here) and that is currently my favorite lens.



 

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