buying a 2nd hand zoom lens

[FilterFunk]

hi, as above the topic,

what do i actually have to look out for when i buy a 2nd hand lens from a stranger?
eg. the things to test/look out for, other than the usual scratches / cracks?

1. focusing speed?
2. look for CA?
3. shoot photos at both ends of the focus range?
4. using different Aperture / Shutter speed settings?

please advice. thanks.

 

[honda]

Look for :
1.external appearance- any signs of damage eg dents, scratch, misalignment and signs of wear n tear as an indicator of usage.
2.tightness or looseness of the focus ring
3.unusual sounds when shaking it
4.scratch marks around the screws that hold the lens together
5.lens surface- small scratch doesn't matter
6.inside of the lens- dust, coating, cracks
7.focus- front or back focus, speed, noise
8.aperture- try all the apertures
9.image quality.
http://singaporephoto.blogspot.com
8

 

[solarii]

May I suggest the following:

http://forums.clubsnap.org/showthread.php?p=2065096#post2065096

BTW some of the criteria you quoted relates directly to the intrinsic characteristics of the lens (ie focusing speed and CA) rather than variables that are affected by use, (ie wear and tear, faults etc.). When buying a 2nd hand lens you should look out for the latter, that are conditions which are affected by use. For the former, you should do your research and try-outs before hand to see if the lens spec is within your standards.

The only intrinsic characteristic that varies is sharpness, which can vary with the copy, but others like focusing speed and CA remain more or less constant. And sharpness can be improved with calibration, which is usually the reason for any significant variation between copies.