Pentax camera/lens combo - practical?

Discussion in 'Pentax' started by Serious_Practitioner, Feb 1, 2006.

  1. Good day, and thank you in advance for your assistance.

    I am beginning to look for a digital SLR - never had digital. I want an SLR
    because more things are eventually possible by varying lenses, not because I
    have really great skills. Also, I'm going to Alaska this year so I want to
    be able to take the best shots I can. Anyway...

    Between us, my father and I have two Pentax film cameras and we like them.
    He uses a Pentax model #SF1n and has a few lenses for it.

    I've read Pentax's Web pages and it seems that the lenses that we have for
    the SF1n will mount to and function with either the Pentax DS or the *istDS.
    So I was wondering if anyone has an opinion on using those lenses, which
    were made for a film camera, on a digital body...

    Thank you again.

    Steve E.
    Serious_Practitioner, Feb 1, 2006
    1. Advertisements

  2. Serious_Practitioner

    Bernd Steyer Guest


    I have heard of no problems so far.
    But I would nevertheless buy the kit lens, too. It is good.
    Bernd Steyer, Feb 1, 2006
    1. Advertisements

  3. Serious_Practitioner

    John Meyer Guest

    Which lenses do you and your dad have? Any of the lenses for the SF1n
    will work on the DS.

    I have a DS and besides the kit lens (which is surprisingly good) I use
    an FA 50mm 1.4 which is just wonderful. It works perfectly on my camera.
    I also us an SMC-A 80-210mm manual focus lens which I also like very
    much. It also works perfectly on the DS, without autofocus of course.

    The excellent viewfinder on the DS series allows for easy manual
    focusing and there is a visual and audible focus assist indicator.

    Keep in mind the crop factor when using film lenses on the DS. Multiply
    the focal length of a film lens by 1.5.

    The DS and *istDS are the same, and have been superseded by the DS2.

    I've been extremely happy with my camera and don't hesitate to recommend
    John Meyer, Feb 1, 2006
  4. My apologies. I'm in the wrong group.

    Steve E.
    Serious_Practitioner, Feb 1, 2006
  5. Serious_Practitioner

    Pete D Guest

    Actually this is exactly the group you want, lots of Pentax users using
    their cameras for good not evil!
    Pete D, Feb 1, 2006
  6. Serious_Practitioner

    corks Guest

    when you guys say kits lens , which one did you mean the 18-50 lens ???
    corks, Feb 1, 2006
  7. Serious_Practitioner

    Pete D Guest

    Probably, they are pretty reasonable, mind you for 4 or 5 times the price
    you can get the Pentax 16-45mm ED AL, very sweet.
    Pete D, Feb 2, 2006
  8. Serious_Practitioner

    RiceHigh Guest

    The lenses with your father's SF1n should be F ones and they should be
    fully compatible with the *ist DS.

    The major concern instead is the 1.535X focal length multipler. Just
    say if you used to have a SMC F 28-80/3.5-4.5 standard zoom lens
    mounted on the DS, it will become a 43-123 lens in terms of the same
    Angle of View. Afterall, you shall need to get also the kit lens, say,
    18-55 (I got mine at only $60), which is equivalent to 28-84 in film
    sense) to cover the missed wide side and this will become the new
    standard zoom.

    Also just wish to remind you that if you have older TTL flashgun with
    your old SF1n, don't get the *ist DL as it don't have the TTL flash
    metering sensor and thus TTL auto flash is not possible. For more
    details, see:-

    Best Regards,
    RiceHigh, Feb 2, 2006
  9. Thank you all. I have to digest this and do some more reading, but this
    raises another question. Why does the focal length of the lens "multiply"?

    Steve E.
    Serious_Practitioner, Feb 2, 2006
  10. Serious_Practitioner

    RiceHigh Guest

    Actually the physical focal length doesn't change. It's just that the
    size of the CCD sensor is changed. 135 film is in 36 x 24 mm and thus
    the diagonal length is 43mm. APS-C DSLRs like Pentax *ist D series ones
    are with CCD of size 15.7 x 23.5 mm (approx.) and thus with a diagonal
    length of 28mm.

    With the change of the sensor size, the image is *cropped* and thus the
    effective Angle Of View (AOV) or Field Of View (FOV) is narrowed. In
    order to obtain the *same* AOV, one must use a wider lens and the
    conversion factor between the "old" and the "new" for equivalent AOV is
    the "mulitplying factor" or commonly called the "crop factor". In this
    case, the crop factor is simply calculated by 43mm/28mm which is
    roughly equal to 1.535X.

    Hope this explains clear enough for your ques.

    RiceHigh, Feb 2, 2006
  11. Serious_Practitioner

    Tony Polson Guest

    It doesn't change. The focal length remains the same. A 50mm lens is
    a 50mm lens whether it is used on 35mm film, medium format film, full
    frame digital or APS-size digital.

    What *does* change is the angle of view. The APS-size sensor is about
    a third smaller than 35mm in width and height. The result is that a
    50mm lens used with an APS-size digital sensor gives a similar field
    of view to a 75mm lens used with 35mm film (or with a full frame
    digital sensor).

    It is difficult for most people to understand the exact effect of a
    change in the angle of view due to the APS-size digital sensor being
    smaller than 35mm film. Because we are familiar with zoom lenses, it
    is much easier for most people to understand the exact effect of
    increasing the focal length by a factor of 1.5 (most DSLRs) or 1.6
    (most Canon consumer DSLRs), hence the idea of a "focal length
    Tony Polson, Feb 2, 2006
  12. Serious_Practitioner

    Bernd Steyer Guest

    And not only that!
    Also the depth of field increases!
    infernal stuff ...
    Bernd Steyer, Feb 2, 2006
  13. Thank you. Those are the clearest answers I've gotten to this question. Even
    the answer I got at a good quality camera shop was less than useful. Thank
    you very much.

    Steve E.
    Serious_Practitioner, Feb 2, 2006
  14. Serious_Practitioner

    RiceHigh Guest

    Yes, Bernd is dead right here. The Depth of Field (DoF) increase with
    the same effective AOV and same aperture number. To get the *same* DoF,
    one will need to open up the aperture more by dividing with the crop
    factor, e.g. for 43mm at f/4 on film SLR, to get the same AOV and the
    *same* DoF on the *ist DS, you need to use a 28mm lens and set the
    aperture to f2.6 which is calculated by 4/1.535.

    For landscape photographers, the increase DoF is something desirable
    sometimes but for portrait photographers, the decreased DoF is often
    something they don't want. :)

    RiceHigh, Feb 2, 2006
  15. Serious_Practitioner

    John Meyer Guest

    Yes, the 'kit lens' refers to the SMCP-DA 18-55mm f/3.5-5.6 AL lens,
    which sells separately for $109 at B&H. Right now the 16-45mm is going
    for $309 after a $100 mail-in rebate. That is a very good value!
    John Meyer, Feb 2, 2006
  16. Serious_Practitioner

    Pete D Guest

    I paid US$70 for my 18-55mm secondhand (I bought it from someone that bought
    a Sigma 18-55mm F2.8 lens) and about US$400 for the 16-45mm and am really
    happy with both. I have not had much of an opportunity to take many shots
    with the 16-45mm but this weekend I intend to take lots, evry review I read
    about this lens raved about just how sharp it is and so far I can only

    Here is the first shot with he 16-45mm.


    Pete D, Feb 2, 2006
  17. Serious_Practitioner

    Tony Polson Guest

    You're very welcome. Glad I could be of help.
    Tony Polson, Feb 2, 2006
  18. Steve-

    At least is a good group for your question.
    Although it seems that the majority of people here are Canon or Nikon
    nuts, there are a few of us who like Pentax.

    I wanted the *ist DS in order to use a 28-70mm f/4 zoom lens I used with
    my film camera. It is a good thing I bought the DS with the kit lens. It
    seems that my particular zoom lens has a chronic problem with lens element
    separation, which I first noticed when it was attached to the new DS body!

    In addition to the kit lens, I've only been able to find a couple of
    Tamron AF zooms locally. However, they are working quite well. I still
    hope to find a store that has a 50mm lens, although I can use an old
    non-AF lens in a pinch.

    So far I've been able to use ALL of my old pentax K-mount lenses. Manual
    focusing can be tricky, since there is no split-image focusing aid, but it
    is helped by using the camera's AF signal.

    There is always a chance a new Pentax body will be announced at the PMA
    show in a few days, so you might wait and see.

    Fred McKenzie, Feb 3, 2006
  19. Will keep an ear out...thanks for the tip.

    Steve E.
    Serious_Practitioner, Feb 4, 2006
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.