I want a new pentax lens.. but...

Discussion in 'Digital Photography' started by Keebler, Sep 8, 2007.

  1. Keebler macrumors 68030

    Jun 20, 2005
    Hi folks,

    I'd like to upgrade my Pentax 50-200 to a 300 type lens. I'd like something in the 400 or better range, but with stabilization, they're way out of my range!

    So, i've been looking at a Sigma 70-300 lens: http://www.sigmaphoto.com/lenses/lenses_all_details.asp?id=3303&navigator=3

    It goes for $320 CDN

    then I saw this guy:

    PENTAX SMC FA J 75-300mm f4.5-5.8 AL - it retails for $249.99 CDN

    The latter is from the 'film era' so a bit older. I did try both lenses and the Sigma appeared to be a tad overexposed, but I will admit that I shot something outside and about 20 mins later so maybe the light affected the shot.

    Any thoughts as to which one is better? I can't seem to find a comparative website b/n these 2 particular lenses.

    Any help would be great.

  2. Keebler thread starter macrumors 68030

    Jun 20, 2005
    btw, i just realize something fairly important - the Sigma lens DID NOT have a UV filter on it, whereas my lens did. that would explain the overexposure a bit now wouldn't it? what a dolt.

    i'm still deciding b/n the lenses though.
  3. Abstract macrumors Penryn


    Dec 27, 2002
    Location Location Location
  4. Steamie macrumors 6502


    Dec 27, 2006
  5. greg555 macrumors 6502a

    Mar 24, 2005
    A filter shouldn't affect the exposure (excluding using the wrong type of polarizer) since the metering is done through the lens and thus includes the filter effect.

    An exposure problem probably means that the aperture closing mechanism isn't accurate enough. Say the camera decides the photo needs f8 and so it moves the aperture lever the specified distance to get f8. But if the lens is not precise enough the actual aperture may be f6.7 (1/2 stop overexposed) or f9.5 (1/2 stop underexposed).

    But if the exposure problem happens when the lens aperture is wide open then there is a different problem.


  6. jpfisher macrumors regular

    Dec 5, 2006
    New Jersey
    The Sigma 50-500mm "Bigma" lens gets excellent marks from the Pentax shooters on dpreview who do nature photography and other applications that require a telephoto zoom. On the other hand, it's quite pricey.

    At the moment, Pentax doesn't have any pro/prosumer grade telephoto zooms in production or readily available on the market.

    Have you considered getting a longer prime lens for telephoto work and possibly a teleconverter? Willing to focus manually? I don't do a lot of telephoto type shooting, but I do have an old manual 300mm f/4 lens and a Tamron 1.4x teleconverter in my bag for when I do.
  7. filmamigo macrumors member

    Sep 17, 2003
    It's actually a current lens. The FA J series are contemporary to the *ist D, and work well on digital bodies. They are not renowned for their build quality, but I really like my FA J 18-35. The FA J lenses from Pentax are like the G lenses from Nikon -- no aperture ring, so you need a newer camera with electronic aperture control, and lighter build to keep the price down for consumers.

    You've done the right thing by testing out the lenses on your camera. I'd go with what works/looks best. If you are happy with the FA J, go for it. Why wrestle with a lens that doesn't give you the performance you want out of the box? (i.e. having to make exposure compensations.)

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