Older Pentax Lenses on Pentax Digtal Bodies

Discussion in 'Digital Photography' started by Anonyma, Jul 9, 2006.

  1. Anonyma

    Anonyma Guest

    I have several wonderful SMC Pentax prime lenses and I just can't bring myself to part with them.

    If I buy a Pentax DSLR it is my understanding that the effective focal lengths will change to higher values, because the chip size of the DSLR is smaller than the film frame size.

    Is there any Pentax or other DSLR that will enable me to make use of my current lenses--even with adapters--and retain their equivalent 35mm focal lengths?
     
    Anonyma, Jul 9, 2006
    #1
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  2. Anonyma <> wrote:
    : I have several wonderful SMC Pentax prime lenses and I just can't bring
    : myself to part with them.

    : If I buy a Pentax DSLR it is my understanding that the effective focal
    : lengths will change to higher values, because the chip size of the DSLR
    : is smaller than the film frame size.

    : Is there any Pentax or other DSLR that will enable me to make use of
    : my current lenses--even with adapters--and retain their equivalent 35mm
    : focal lengths?

    Not a big problem. First from personal experience I found that the change
    is minimal and you will quickly get used to the effect of the change. But
    if you really must have the focal length be the same, use a .6 or .7x
    supplemental lens that screws onto the filter threads. This will offset
    the reduction in angle of view presented by the smaller sensor. If
    you have several lenses with different filter sizes, I suggest getting the
    supplemental lens for the largest filter threads you have and then use
    filter adapters to adjust the supplemental lens to the smaller filter
    sizes. This will keep all vignetting problems at bay and mean that you
    only have to have one expensive supplemental lens.

    Now if you are using zooms and do your composing using the viewfinder you
    will be better off just using your old lenses. The main effect of the
    "multiplier" is that your lenses will now extend much further into the
    "long" end and be much worse at the "wide" end. Which may inspire you to
    add one more "extreme wide angle zoom" to your kit to reclaim your wide
    angle.

    Randy

    ==========
    Randy Berbaum
    Champaign, IL
     
    Randy Berbaum, Jul 13, 2006
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  3. Randy Berbaum wrote:
    > Anonyma <> wrote:
    > : I have several wonderful SMC Pentax prime lenses and I just can't bring
    > : myself to part with them.
    >
    > : If I buy a Pentax DSLR it is my understanding that the effective focal
    > : lengths will change to higher values, because the chip size of the DSLR
    > : is smaller than the film frame size.


    Think of it as getting an extra 1.4x teleconverter for free built in
    the camera. The extra magnification may make some weaker old lenses
    look a bit iffy at the edge of field. OTOH it is a positive benefit for
    long focal length lenses since you get more magnification without any
    loss of light.
    >
    > Not a big problem. First from personal experience I found that the change
    > is minimal and you will quickly get used to the effect of the change.


    I don't find it an issue - except for very wide field images.

    > if you really must have the focal length be the same, use a .6 or .7x
    > supplemental lens that screws onto the filter threads. This will offset
    > the reduction in angle of view presented by the smaller sensor.


    This is not a good idea. They really are quite poor performance with
    chromatic aberrations visible at edge of field (though better than
    nothing if needs must).

    Tthe only old Pentax lens I really miss using on my istD is a 17mm
    fish-eye.
    That still needs a film camera to be used effectively.

    Regards,
    Martin Brown
     
    |||newspam|||@nezumi.demon.co.uk, Jul 13, 2006
    #3
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