Checking quality on a lens

jswoolf01jswoolf01 Registered Users Posts: 31 Big grins
edited February 5, 2008 in Accessories
Help needed, please:

About three weeks ago, I bought a secondhand 80-200mm f/2.8 lens for my Nikon D80 dSLR. I've used it several times on various occasions under various conditions. I've found that while the low-light performance is as advertised, there are two or three things about it that concern me. I wonder if someone who has the same model lens could offer some thoughts.

1) the focusing motor often engages and disengages with an audible [thunk] that almost always makes the lens and camera flinch a bit. Is this normal, or is there something wrong with the motor?

2) sometimes the lens changes focus as I move it around, as if it's in continuous-autofocus mode when the camera is set to single-focus mode.

3) the photos I've taken with this lens often appear to be a little on the soft side. The descriptions and reviews I read before buying said the lens is tack-sharp, but that doesn't match the results I'm getting. Here's an example. This Short-eared Owl was flying past me about 30-40 feet away, and I was panning with it. Zoom was at maximum, 200mm. ISO was 1600. Shutter speed was 1/500 and aperture f/14 -- fast enough to freeze motion, aperture small enough to get decent DOF.

Short_eared_owl_flying_01.jpg

(Note: this version was cropped and reduced in size from the original, and slightly sharpened using Unsharp Mask in Photoshop Elements 5.)

A second shot taken about two seconds later, also reduced, cropped, and unsharped in PSE5:

Short_eared_owl_flying_03.jpg

Is this typical performance for this lens? I expected it to be sharper -- am I expecting more than the glass can actually deliver?

-- JSW

Comments

  • eyusufeyusuf Registered Users Posts: 236 Major grins
    edited February 5, 2008
    little bit difficult to judge how the lens performs based on a moving object. i always test focus and sharpness by doing a controlled test. very easy to do and takes literally 5 mins. just set your camera on a tripod and take pics of something with good contrast, i.e. book, newspaper, or the box of your lens. use center point focus and timer. fire away at various focal lengths and aperture, and see how it performs.

    can't comment on your concerns on 1) and 2).
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