SMC Pentax-M & -A series lens schematics

Discussion in 'Pentax' started by Malcolm Stewart, Apr 5, 2005.

  1. I've searched without success for lens schematics for SMC Pentax-M & -A era
    lenses.
    The two I'm particularly interested in are the :-
    SMC Pentax-M 28mm f2.8 #7295xxx
    SMC Pentax-A 28mm f2.8 #5384xxx

    Why the interest? Because the later -A version is slightly longer and
    weighs 10g more - at a time when most items were getting smaller as time
    went by. The -A version appears to have better coating, but the optical
    construction is also quite different with the aperture blades set at a
    different level, and yet independent reviews of the -M version were quite
    complementary about its performance. So why make the changes ?

    Any pointers to URLs would be very welcome. (I've checked the obvious
    ones.)
    Could the smaller -M version have been using <potentially polluting> lead
    based glass? Also, the -A version seems reticent about its country of
    origin, whereas the -M clearly states Japan.

    Thanks
     
    Malcolm Stewart, Apr 5, 2005
    #1
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  2. Malcolm Stewart

    Guest Guest

    Malcolm Stewart a écrit :
    The "Bible" for Pentaxians:
    http://kmp.bdimitrov.de/
     
    Guest, Apr 5, 2005
    #2
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  3. "michel.[pas]carrere-[de]gee[spam]"
    Many thanks. It's an excellent site which I had visited during my search,
    lots of info but no schematics.
    It does have a table stating that both of my lenses are 7 group / 7 element
    designs. The reflections are so different that I'm having trouble believing
    that that really is the case.
     
    Malcolm Stewart, Apr 5, 2005
    #3
  4. Malcolm Stewart

    Mark Roberts Guest

    It does indeed have the schematics: Just go to the individual page for
    the lens in question
    (http://www.bdimitrov.de/kmp/lenses/primes/wide-angle/M28f2.8-ii.html,
    for example) and click on the optical formula ("7 elements in 7 groups"
    in this case) to get this:
    http://www.bdimitrov.de/kmp/lenses/primes/_optics/28f2.8-ii.gif
     
    Mark Roberts, Apr 5, 2005
    #4
  5. Many thanks - I must check my monitor settings and/or my spectacles!.
    I'd missed seeing the underlines below the names of the lenses in the
    tabular listing. And, the schematics are indeed quite different for the
    pair of lenses in question.
     
    Malcolm Stewart, Apr 5, 2005
    #5
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