The real Bigma - or How High The Moon?

Discussion in 'Digital Cameras' started by ASAAR, Nov 30, 2006.

  1. ASAAR

    ASAAR Guest

    From the Dec. PP&I comes a brief mention of a new Zeiss lens,
    custom manufactured for a private client. Intended for use on a
    Hasselblad 203 FE to "photograph wildlife at a great distance", its
    focal length is 1700mm and weighs in at 564 pounds. Aperture and
    cost not given, but a small photo of this BWL is on the bottom
    corner of page 18. Anybody know what the effective focal length
    would be if it could be adapted for use with an APS sensor DSLR?
    ASAAR, Nov 30, 2006
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  2. It's a 1700/4.0.

    From a thread on the MF list: (where there was a link to a photo that's
    since been taken down).
    Actually this Zeiss statement is hype: Canon made 5000mm lenses for the
    1964 Tokyo Olympics which came with their own pedestal and seat, and
    had a nitrogen bottle attached so that the photographer could flush the
    internal environment of the lens. You could mount a canon FT on it, as
    well as a TV camera. When I worked in Photo-Retail in Pennsylvania in
    the 80-s, I had an Oil-millionaire ask me if I could find one for
    him... then the oil bust....

    David J. Littleboy
    Tokyo, Japan
    David J. Littleboy, Nov 30, 2006
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  3. ASAAR

    Neil Ellwood Guest

    Just imagine hand holding it - two and a quarter cwt. :-(
    Neil Ellwood, Nov 30, 2006
  4. ASAAR

    Bob Williams Guest

    APS size sensors have a magnification factor of about 1.6X vs Full Size
    35 mm film. So the Equivalent focal length on an APS DSLR would be a
    whopping 2720 mm!!!!
    Bob Williams
    Bob Williams, Nov 30, 2006
  5. ASAAR

    ASAAR Guest

    Probably not well suited for the veldt.

    Methinks dpreview needs to hear the voice of an expert:
    ASAAR, Nov 30, 2006
  6. ASAAR

    Guest Guest

    this one?

    Guest, Nov 30, 2006
  7. ASAAR

    ASAAR Guest

    Whoops! Check again. The lens was built for a Hassy, not a D5,
    so it should be quite a bit longer than 2,720 mm! :)
    ASAAR, Nov 30, 2006
  8. ASAAR

    SimonLW Guest

    If my calcs are any good, it gives the angle of view of something like a
    SimonLW, Nov 30, 2006
  9. ASAAR

    ASAAR Guest

    It's hard to pin it down because telescopes can be lighter than
    some lenses. But by the time a lens weighs more than the
    photographer (in this case 2 to 3 times as much), and you might
    think that the mount is where the photographer sits, I think that
    most people would agree that we've exited the realm of lenses. :)
    ASAAR, Nov 30, 2006
  10. ASAAR

    ASAAR Guest

    If you missed anything, it's that I didn't ask for the actual
    focal length, which as you point out is obviously already known. I
    asked for the effective focal length, which is a function of the
    actual focal length and the sizes of the cameras' sensors.
    ASAAR, Nov 30, 2006
  11. ASAAR

    ASAAR Guest

    Thanks. It's interesting that the other lens, mentioned by David
    is an actual 5200mm (5,150 in the spec's). But the Canon designed
    lens uses mirrors, and at 220 lbs. is less than 1/2 the weight of
    Zeiss's glass. The mirror lens also is said to use ND filters, so I
    guess that the Zeiss lens chalks up another advantage with its
    (assumed) diaphragm.
    ASAAR, Nov 30, 2006
  12. ASAAR

    ASAAR Guest

    I understand what you mean about the crop factor being fixed at
    1.6 (or 1.5) when comparing an APS sensor to a FF sensor, and the
    lens is 1,700mm for all cameras. But there's also a crop factor to
    account for when comparing a FF camera to the Hasselblad with its
    larger sensor, and the difference in size between the images
    produced by the APS sensor and the Hassy's would be even greater
    than the difference between the APS and FF sensors.

    The problem is that the base being used for comparison is the FF
    sensor, but what I was after was the effective difference in focal
    length using the Hasselblad's sensor as the basis of comparison, not
    an FF sensor. If we had the crop factor of the Hasselblad's sensor
    vs. an APS sensor we'd simply multiply 1,700 by that constant. If
    we have that, would the effective focal length of the APS camera
    relative to the Hasselblad be 5200mm or something else? The world
    revolves around FF sensors only for a subset of Canon and Kodak DSLR
    owners, ya know. <g>
    ASAAR, Nov 30, 2006
  13. ASAAR

    Eric Miller Guest

    What he probably doesn't understand is that, in comparison to FF 35mm, there
    is a "reverse crop factor" for medium format. I.e., on the Hassy, a 1700mm
    lens would have the same field of view of a much shorter lens on a 35mm
    camera. Because the 1.6 - 1.5 of APS sensors is a ration derived from
    comparison to FF 35mm, you can't use the 1700 focal length as part of the
    equation used to determine the effective focal length comparison of APS to
    Medium Format. In order to to compare APS to Medium Format, under the
    "comparison to FF 35mm" nomenclature, you would first need to start with the
    shorter apparent focal length of Medium Format in comparison to 35mm. So the
    medium format film would have a .6, more or less (couldn't find the exact
    number), reverse crop factor. So in comparison to the fov on a 35mm camera,
    the 1700mm lens would have the same field of view of a 1020mm lens. So if
    you want to use the crop factors of both 35mm and APS, then you must start
    with 1020mm (more or less) to get the right result. Of course, you should
    come up with the same apparent focal length by simply multiplying 1.6 x
    1700, but that is apparently just too easy.

    Eric Miller


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    Eric Miller, Nov 30, 2006
  14. ASAAR

    Bill Funk Guest

    From the description I read, it doesn't autofocus with anything. :-(
    Bill Funk, Nov 30, 2006
  15. ASAAR

    ASAAR Guest

    No. That's exactly the point I tried to make. And the same focal
    length lens on an FF camera would have the same field of view as a
    shorter lens on the APS camera. So these individual differences, or
    let's say, crop factors, would each be less than the crop factor of
    an APS sensor that was based on a comparison with a sensor the size
    of the Hasselblad's sensor, instead of the more commonly compared FF
    (35mm film size) sensor.

    True, unless it's just a part of a more complex equation.

    Too easy is correct. If the reverse crop factor used for FF and
    Hassy comparisons is 0.6, then wouldn't the crop factor of APS
    sensors (when compared to Hassy sized sensors) be on the order of
    1.6 * (1/0.6)? This would indicate that a 1,700mm lens on the Hassy
    would be comparable to 2833mm (1,700 / 0.6) on a FF camera and
    4,533mm (1,700 * 1.6 / 0.6) on an APS camera. But a 1,700mm lens on
    a FF camera would be comparable to 2,720mm (1,700 * 1.6) on the APS
    camera. Based on the last of your sentences quoted above, it would
    appear that there's little to no difference between a Hassy sensor
    and a FF sensor, since the 1,700mm lens on either would be
    comparable to 2,720mm when used with a camera with an APS sensor.
    Is that what you really meant or did I misread it?
    ASAAR, Nov 30, 2006
  16. You're over-complexifying things.

    The lens has a focal length of 1700mm. On a 35mm full-frame camera, that
    corresponds to a certain field of view. On a camera, like the
    Hasselblad, that has a bigger active area, the field of view is bigger.
    Hence, the 'blad sees a FOV that is the same as a 35mm camera with a
    shorter lens, so the lens has a "Hasselblad-effective" focal length of
    maybe 1000mm.

    On a camera with a smaller active area (ie an APS-C sensor
    camera), the field of view is smaller, corresponding to what a 35mm
    camera would see if it had a 2800mm lens.

    Daniel Silevitch, Nov 30, 2006
  17. ASAAR

    SimonLW Guest

    The key term is "angle of view". Many compact digital cameras have zoom
    lenses of, say, only 5 to 23mm. This means little to the typical user
    because there are numerous sensor sizes. Manufacturers often list the
    equivalent focal length for the same angle of view the lens provides if it
    were designed for a 35mm film camera. 35mm is often used as a standard due
    to it's former popularity. In this example it could be a 38 to 140mm lens.

    Most people are familiar that a 50mm on a 35 mm camera is about "normal",
    not wide nor long. If it were possible to mount that 50mm lens on a digital
    compact camera, the FOV becomes equivalent to about 400mm lens on 35mm.

    If that hassy is 6x6 film, the diagonal measurement across the film plain is
    about 3 times that of a APS sensored dSLR, thus the angle of view shrinks
    down as if it were a 5200mm equiv. lens on the hassy.
    SimonLW, Nov 30, 2006
  18. ASAAR

    ASAAR Guest

    I understand that perfectly well. I've already acknowledged that.
    How hard it is for YOU to understand this?
    ASAAR, Nov 30, 2006
  19. ASAAR

    ASAAR Guest

    You're missing the point.

    With the 1,700mm lens as used on an APS camera, what focal length
    would be needed to get the same FOV on an FF camera? I get 1,700 *
    1.6, or 2,720mm.

    With the 1,700mm lens as used on an APS camera, what focal length
    would be needed to get the same FOV on the Hasselblad? I get 1,700
    * 1.6 * (1/0.6), or 4,533mm. The 1/0.6 factor was based on Eric's
    reverse crop factor of 0.6, used for comparing the Hasselblad with
    an FF camera. Would you get a focal length substantially different
    than 4,533mm?
    ASAAR, Nov 30, 2006
  20. ASAAR

    SimonLW Guest

    I don't assume eveyone knows about the "effective FL issue" clearly. The
    last line in my previous post answered the question.
    Your 2550mm "effective FL on 35mm is not correct. 6x6 has a diagonal measure
    (~85mm) of about twice that of the 35mm film frame (43mm). This gives is
    about 2x crop so the lens is effective 3400mm. On a APS sensor, the diagonal
    of the 6x6 frame is 3 times so the efective FL is around 5000mm.
    SimonLW, Nov 30, 2006
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