Extension tube on d70/rebel xt kit lens?

Discussion in 'Digital SLR' started by Brian, Jun 13, 2005.

  1. Brian

    Brian Guest

    Anyone tried this? If so, with what level of success? (I don't have
    either [yet], but I'm thinking about the potential of maybe being able
    to use the kit lens for some macro work)?

    Any comments?

    Thanks! Brian
     
    Brian, Jun 13, 2005
    #1
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  2. Brian

    Frederick Guest

    I have tried it with the D70 and 18-70 kit lens with surprisingly good
    results. (I didn't think that tubes on a short zoom lens was a good
    idea) One 13mm tube was all that I needed to get to about 1:2 ratio.
    Using combination of zoom and focus, a 13mm tube seems to get from about
    35cm to about 3 or 4 cm at 70mm.
    The D70 kit lens is IF (internal focus), and does not focus anywhere
    near as close as the Canon 18-55 kit lens.
    If you get tubes, make sure that you get ones with the electronic
    contacts so that you get metering.
     
    Frederick, Jun 13, 2005
    #2
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  3. Brian

    Brian Guest

    Thanks for the info! Just to clarify...are you saying that normally
    the min focus distance is 35cm for the D70 kit lens @ 70mm but with the
    13mm extension tube it is reduced to 3 or 4cm...is that correct?

    By the way, I have never used extension tubes before... :) Do you know
    if there is a ratio or some formula that can indicate what
    magnification and focus distance would be attained with different
    length tubes?

    Thanks, Brian
     
    Brian, Jun 13, 2005
    #3
  4. Brian

    DoN. Nichols Guest

    I believe that he means that the kit lens, mounted on the 13mm
    tube and set to 70mm zoom, will focus between 35 cm (13.7") and
    somewhere between 3 to 4 cm (1.18" to 1.57").
    With relatively simple prime lenses (fixed focal length) you
    should be able to calculate what the effective range would be. But you
    would need to know just how far the focus adjustment moves the lens.
    With internal focus lenses, telephotos and wide angle lenses, and
    especially with zooms, there are too many things going on optically to
    make it easy to predict the results. The best bet is to grab the lens
    and the set of extension tubes and experiment. (Or, if you want fewer
    pieces to juggle, try a bellows instead.) Hmm ... does Nikon offer a
    bellows with the electrical contacts for the CPU lenses?

    Enjoy,
    DoN.
     
    DoN. Nichols, Jun 13, 2005
    #4
  5. Brian

    eawckyegcy Guest

    eawckyegcy, Jun 13, 2005
    #5
  6. Brian

    Frederick Guest

    Yes - that is correct. Zooming back below 50mm the minimum focus
    distance becomes so close that it is practically unusable - and
    pointless as the magnification ratio is no better than achievable at 70mm.
    AFAIK, no they don't. But, I the tubes that I have are "marumi" brand,
    and it looks like they could be disassembled and the mounts with
    contacts used to construct "CPU" bellows. Some creative engineering
    would be needed to connect the aperture stop-down lever between the lens
    mount and body mount.

    For the OP, the canon 18-55 kit lens is not IF, and your paragraph above
    explains why a 13mm tube would probbaly give a completely different
    result on that lens. The Canon 18-55, including the so-called "mark II"
    on the 350D is a very special piece of equipment. I was using one the
    other day, and took some very soft shots with a 350d. For photography,
    a body cap is possibly a less expensive and more useful accessory for a
    Canon DSLR owner. ;-)
     
    Frederick, Jun 13, 2005
    #6
  7. Brian

    Brian Guest

    Hey, thanks for the additional info and the link (which after a quick
    overview seems like it might take a while to get through) - very
    helpful!



    Brian
     
    Brian, Jun 13, 2005
    #7
  8. Brian

    Brian Guest

    what is the focusing distance with the body cap? j/k!
     
    Brian, Jun 13, 2005
    #8
  9. Brian

    eawckyegcy Guest

    You can google up almost every optical equation under the Sun. Your
    specific question is answered by adding "e/f" -- e == extension, f ==
    focal length -- to the non-extended maximum magnification the lens.
     
    eawckyegcy, Jun 13, 2005
    #9
  10. Brian

    DoN. Nichols Guest

    Which probably explains why my "28-105mm f3.5-4.5 D" Nikon lens
    limits the zoom range from 50mm to 105mm when the macro mode is engaged.
    You would also need to add something to the bellows to allow it
    to compute the variable aperture loss when the lens is moved out on the
    bellows. I think that really, with a bellows, you do need to stick with
    a manual mode of operation.
    A spectacular endorsement. :)

    Enjoy,
    DoN.
     
    DoN. Nichols, Jun 13, 2005
    #10
  11. 350d kit lense works well with tubes *that it fits*. The construction
    allows you to add up about 70mm tubes at 35mm focal lenght without
    the focus point being located inside the lense. That makes the front
    almost touch the subject and gets you at 2X magnification!

    The construction of the lens means a lot. For example, my Sigma
    18-50/2.8 allows only 25mm at 50mm focal lenght or the front element
    hits the subject.

    Beware, most extention tubes do not fit EF-S lenses. EF-S lenses have
    the extending plactic part at the back of the lense and it won't fit in
    all extention tubes (including older canon tubes). My tubes are modified
    because of that.
     
    Harri Suomalainen, Jun 14, 2005
    #11
  12. Brian

    Dave Guest

    Brian,

    With your lens at infinity focus and an extension of 35mm you can get to
    1/2 life size. With 70mm of extension you would get life size.

    Fl/extension = reproduction ratio. Use actual FL of lens!!

    How close it will focus (working space) depends on focal length.

    If it were me, I'd opt for one of the Nikon or Canon high-end diopter
    "filters". With extension tubes you lose 1 stop of light at 1/2 life
    size and 2 stops at life size. (Remember, you'll need to stop down for
    depth of field), with diopters you won't lose any light.

    I've seen some very nice work done with the Canon version (250D for
    lenses under 200mm and 500D for over 200mm) and I'm sure the Nikons (5T
    & 6T I think) would do as well, but only come in 52 and 62mm sizes.

    Hope this helps,
    Dave
     
    Dave, Jun 14, 2005
    #12
  13. Brian

    Dave Guest

    SHOULD BE Ext/Fl
     
    Dave, Jun 14, 2005
    #13
  14. Brian

    Paul Furman Guest

    You can also use a canon on a nikon, it doesn't matter. That's correct
    that they are rated/designed for a given focal length range but that
    doesn't seem very critical. I got the canon 500D +2 diopter for my 200mm
    lens but here's a test on my 45mm lens:
    <http://www.edgehill.net/1/?SC=go.ph...-garden/more/2005-06-12-triteleia&PG=1&PIC=1>
    Full pixels crop and looks darn sharp to me. Better than I got from the
    big lens, maybe because that one is a zoom & the 45mm is a prime.

    Also you may not need a large one on a long zoom because you will only
    use it at full telephoto, you'd have to check that at a camera shop
    before buying.
     
    Paul Furman, Jun 15, 2005
    #14
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