I’ve been asked in the past what I do to test out a lens when buying used or even when buying a new lens. Typically when buying used from a character off the internet you can only do so much given the meeting time probably won’t be that long to perform extensive tests outside of making sure it’s physically okay and taking a few snaps. However, once you have the lens in your hands at home (new or used) there are several tests you can perform to really figure out the nuances of your lens, some straight forward and some more advanced that the typical shooter wouldn’t really think of performing.
I’ve read several online articles and just chatted with other photographers as to what they do to test out lenses, however I’ve found a decent guide online that sums up a lot of key testing methods on lensrentals.com. I highly recommend checking it out at least for a few of the more basic physical tests you can do to a lens (some very obvious). There are a couple of advanced techniques used to identify how your lens focuses at various lengths which can help greatly if you care to utilize the micro-adjustment function in more advanced camera bodies. Anyhow, here’s the link to the guide : “How to test a lens”.
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