Correcting the multiplication factor on DSLR's/optics question

Discussion in 'Digital Photography' started by barronchung, Feb 7, 2006.

  1. barronchung

    barronchung Guest

    I have been contemplating getting a DSLR for a while, but the
    multiplication factor on the lenses has made me want to wait until
    full-frame CCD's become less expensive. I contemplated adapting my old
    digital camera to take Nikon lenses after I found this:

    http://www.davearney.org/cam/

    So I tried something similar with my old digital camera:

    http://barron.cfdeveloper.co.uk/makepage.cfm?Page=HP120

    Then, I found this article where someone has converted a Casio digital
    camera to take Leica m39 tread mount lenses:

    http://www.digit-life.com/articles2/m39var1/

    However the multiplication factor was an even bigger issue because the
    CCD was even smaller than on a DSLR. Now, I'm really curious as to
    whether or not someone could make something usable with an F-mount. I
    sold my old (crappy) HP and got a cheap (sold as a "parts" camera) 2
    megapixal Nikon to sacrifice. What I was wondering is if it's possible
    to add some optics in front of the CCD that would shrink the incoming
    image so that the multiplication factor wouldn't be so big? At first, I
    was thinking of just adding a wide-angle converter to the front of the
    lens, but then you're still just taking a crop of the full image
    available--i.e., you lose the resolution of the lens. Is it possible to
    use a wide-angle converter between the lens and camera body (like you
    do with a teleconverter) to grab more of the incoming image? I'm
    guessing a consumer point and shoot CCD won't really notice a
    difference in the loss of lens resolution from taking a crop of the
    full image available, but it would also be much more convenient if the
    wide-angle converter is permanently fixed to the body and you don't
    have to add a wide-angle converter to a lens every time you switch
    lenses. I'm sure someone out there is screaming "blasphemy" or "moron"
    but I really don't know enough about the optics except what I've seen
    on those websites and tried myself. I couldn't find any information on
    the Internet on the placement of wide-angle lenses on the back-end.

    On a side note, I was interested in taking out the electronics of the
    digital and placing them inside an old Nikon body, so that the rig
    looks like a real DSLR. But, I don't have a spare body. If anyone knows
    where I can get a cheap non-functional body, or has one they wouldn't
    mind donating to a "good cause", I would appreciate that too. Call me
    old-fashioned, but I just can't justify sacrificing a working Nikon
    just to see if my Frankenstein camera can work.
     
    barronchung, Feb 7, 2006
    #1
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  2. barronchung

    Paul Furman Guest

    Just get a DSLR. They have much larger sensors than 'regular' digital
    cameras and that provides better quality images, especially low light
    high ISO performance. The only difference is you may need a new wide
    angle lens to compensate for the size difference. Full sized sensor
    DSLRs are very expensive and that probably won't change soon.
     
    Paul Furman, Feb 7, 2006
    #2
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  3. barronchung

    barronchung Guest

    Just further on the bit about mounting it inside an SLR: I was planning
    on replacing the focussing screen with the LCD screen, so you get the
    feeling that you're using a regular SLR. In practice the parts may not
    all fit in the body the way I vision, but it would be an interesting
    project nonetheless.
     
    barronchung, Feb 7, 2006
    #3
  4. True. But...
    The extra US$1800 or so the 5D costs seems pretty cheap compared to the
    headache of having to multiply or divide by 1.6 every time you think about
    taking a photograph...

    David J. Littleboy
    Tokyo, Japan
     
    David J. Littleboy, Feb 7, 2006
    #4
  5. barronchung

    Bruce Hoult Guest

    The extra US$1800 or so the 5D costs seems pretty cheap compared to the
    headache of having to multiply or divide by 1.6 every time you think about
    taking a photograph...[/QUOTE]

    I think most of us fall into one of two categories:

    1) those who put the camera on a tripod, use a tape measure to find the
    exact distance to the subject and the size of the subject, calculate
    which lens they'll need, put a light meter up against the subject,
    calculate the exposure by hand, set the aperture and shutter speed.

    2) those who look through the viewfinder and twist the zoom until it
    looks right.


    Those is the first group can and do cope with all sorts of film/sensor
    sizes and lens focal lengths and wouldn't even remark on the calcualtion
    to fgure the fiield of view from those becuase they've alwasy been doing
    it *anyway*.

    Those in the second group don't know or care what numbers are printed on
    the lens. They'll have a wide angle lens and bring-distant-stuff-close
    lens and who cares what the numbers say?


    The crop factor is something they think about when deciding what to buy
    but not, that I can see, something that you think about when taking a
    photo.
     
    Bruce Hoult, Feb 7, 2006
    #5
  6. barronchung

    ASAAR Guest

    True, but people could choose a different brand DSLR and not only
    save far more than US$1800, but spare themselves the complex math.
    headaches by getting a camera having a 2.0 crop factor. This sensor
    isn't quite as large as those in other DSLRs, but compared to the
    digital P&S cameras having tiny sensors with truly 'insanely small
    pixels', the 2.0 factor sensors are virtually olympian sized. :)
     
    ASAAR, Feb 7, 2006
    #6
  7. barronchung

    BobF Guest

    If you want to build your own camera... try to get some lenses from old 16mm
    movie film cameras... some were adapted to video security use in the 70s, EG the
    Shibaden camera... they throw a smaller image... I used to have some but sold
    them a while back...
     
    BobF, Feb 8, 2006
    #7
  8. Essentially, you need a specialized piece of optics to shrink the scale
    of the image, sort of like a telescope operated in reverse. But, it
    needs to operate in the converging-rays environment between lens and
    sensor, not the parallel-rays environment of an ordinary telescope (so
    literally using a telescope in reverse isn't likely to work).

    In addition, you want the final image to have much higher resolution
    (in terms of lp/mm) than what the original lens could achieve. More
    precisely, you want the final image to have the *same* resolution when
    measured in terms of line pairs per picture height, but if the sensor is
    1/5 as high as the lens was originally designed for (which is about
    correct for the better P&S digicams), the image is 1/5 as large, and you
    need 5 times more line pairs per mm to get the same number of line pairs
    per picture height. So if the original lens resolves 50 lp/mm nicely,
    your conversion optics need to resolve 250 lp/mm on the output side -
    quite a challenge. Oh, and you want perfect colour correction (no added
    colour fringes) and flat field.

    On top of that, the conversion optics needs to accept all the light that
    comes through the main lens up to some f/number, preferably wide open.
    If you're going to use multiple "main" lenses, the conversion optics
    have to do this for all of the possible exit pupil locations for all of
    those lenses.

    In short, making this work well is a very difficult optical problem,
    more difficult than just designing a new lens for the smaller sensor
    from scratch. Someone (Nikon?) did do this once, but abandoned it.

    Dave
     
    Dave Martindale, Feb 8, 2006
    #8
  9. I think most of us fall into one of two categories:

    1) those who put the camera on a tripod, use a tape measure to find the
    exact distance to the subject and the size of the subject, calculate
    which lens they'll need, put a light meter up against the subject,
    calculate the exposure by hand, set the aperture and shutter speed.

    2) those who look through the viewfinder and twist the zoom until it
    looks right.


    Those is the first group can and do cope with all sorts of film/sensor
    sizes and lens focal lengths and wouldn't even remark on the calcualtion
    to fgure the fiield of view from those becuase they've alwasy been doing
    it *anyway*.

    Those in the second group don't know or care what numbers are printed on
    the lens. They'll have a wide angle lens and bring-distant-stuff-close
    lens and who cares what the numbers say?


    The crop factor is something they think about when deciding what to buy
    but not, that I can see, something that you think about when taking a
    photo.
    [/QUOTE]
    I think there are a lot of people in between those two groups....Or, they
    are gradually going from the second group toward the first........
     
    William Graham, Feb 8, 2006
    #9
  10. I think correcting the multiplication factor will be the least of your
    problems.....Before you're done, you'll wish you had just bought a good
    digital camera......Consider Fuji's S3.....(If you have a bunch of Nikkor
    lenses)
     
    William Graham, Feb 8, 2006
    #10
  11. barronchung

    Ray Fischer Guest

    Given that the problem can be solved with some masking tape applied to
    the lens and a pen, the extra $1800 to solve a non-problem seems
    pretty ridiculous.

    Unless you're just trying to justify $3300 for a camera.
     
    Ray Fischer, Feb 8, 2006
    #11
  12. Seriously, if you thought I was being serious there, your sense of humor is
    seriously defective.

    David J. Littleboy
    Tokyo, Japan
     
    David J. Littleboy, Feb 8, 2006
    #12
  13. barronchung

    tomm42 Guest

    Since it sounds like you really want to do this, stick good lens on a
    lousy sensor. Sensors have gotten much better. You can do what Sony
    used to do and put camcorder lenses on your Frankenstein. 15mm -40mm
    lenses for C-mount cameras can be found fairly easily and cheaply (as
    long as they are not Zeiss). The cheapest would be the normal 25mm.
    Thsi would still be a little large for a P&S sensor but would still
    have enough depth of field fudgability since you won't be able to
    focus. The back focus of the lens would be closer to the original
    digicam lens. I wish you luck.

    Tom
     
    tomm42, Feb 8, 2006
    #13
  14. barronchung

    Doug Robbins Guest


    Complex math? Multiplying by 1.5 or 1.6 is "complex math"? Did you graduate
    the third grade? Damn, educational standards have fallen!

    Doug

    BTW, solving non-linear differential equations is complex math (at least for
    me). Simple multiplication should be considered as essential as being able
    to read traffic signs and make change.
     
    Doug Robbins, Feb 8, 2006
    #14
  15. barronchung

    ASAAR Guest

    To quote DJL:
    I got it. You didn't. Add *your* name to the list of the
    humor impaired since I believe that whatever humor I contributed was
    at least slightly more obvious than David's.. :) And FWIW, though
    it really doesn't matter much, in university higher math. courses I
    got nothing but the highest grades, to the point where on some
    exams, for the first time my instructor had to ignore my scores
    because, as he told the class, they "broke the curves". That
    doesn't mean that education standards haven't fallen, but if they
    have, it's probably due more to those such as yourself, who all too
    easily read without fully comprehending.
     
    ASAAR, Feb 8, 2006
    #15
  16. barronchung

    Doug Robbins Guest

    and add *you* to the killfile of usenet assholes.
     
    Doug Robbins, Feb 8, 2006
    #16
  17. barronchung

    ASAAR Guest

    Thus demonstrating that humor impairment is the least of your
    problems. I'll bet you've got a large killfile. :)
     
    ASAAR, Feb 8, 2006
    #17
  18. barronchung

    barronchung Guest

    I think you hit the nail on the head here; I'm pretty much in the
    second group and as William described, gradually going from the second
    group toward the first. What it boils down to in my Frankenstein
    project is whether the sensor size will crop too much out of the image
    and make even a wide-angle lens unusable for everyday shots. I guess I
    would end up with a macro- or landscape-only camera with
    interchangeable lenses, which may be useful to some but not others.
     
    barronchung, Feb 8, 2006
    #18
  19. barronchung

    barronchung Guest

    Thanks, Dave. This is the kind of technical info I was lacking. I guess
    I have to deal with the fact that the optics don't work that way and
    have all my lenses x5, or just don't bother with Frankenstein.
     
    barronchung, Feb 8, 2006
    #19
  20. barronchung

    barronchung Guest

    Well, photography is a hobby, and so is electronics, which is why I was
    contemplating this project. The best way for me to find the "hobby
    money" to throw at a "real" DSLR is to sell my film cameras and lenses,
    which would pretty much mean that there's no reason I have to stick
    with a Nikon mount. At which point, I may as well just invest in a
    really good consumer digital of any brand that has the best value and
    features for whatever money I could get. Frankenstein is just an
    interesting project I thought I could try; I think I was more
    interested in the process (a.k.a., playing with gizmos) than in making
    something that was of a professional grade. The multiplier factor was
    something that I thought may be possible with my limited knowledge of
    optics, but now thanks to Dave I realize it's not possible. I am the
    result of what happens when a Tinker Toy or Lego child grows up-- I
    used to take things apart to see how they worked; maybe I couldn't get
    them back together but I sure had a lot of fun in the process!
     
    barronchung, Feb 8, 2006
    #20
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