How to Detect Physical Flaws in a Used Camera Lens

This is an interesting link posted by Pentax Malaysia facebook page and I think it's a great article everyone should read if they buy pre-loved lenses. Yes, pre-loved. What a romantic way of saying second hand or used, or at least that is what you want to believed it was treated with the lens you are about to buy!

Click here to read full article: How to Detect Physical Flaws in a Used Camera Lens

It pretty much sums up all the things you have to look at. Here are some other tips I can think of:

• bring a little torch light in case you don't have good light available when you meet up with the buyer
• check for hazing in the lens. although this is quite apparent, the initial stages of hazing can be hard to detect
• test autofocus accuracy. most cameras today has autofocus micro adjustments (Pentax k-7 and  k-5 has it. k-x requires a firmware "hack"), so this isn't such a major issue, but can be a little frustrating when you find out your lens isn't as sharp as all those reviews rave about. to do a quick test, just set your camera to center focus, single shot AF, shoot at longest focal length (for zooms) and at closest focusing distance to a picture with good contrast. after taking the photo, zoom in and check if the photo is sharp. Not the most proper way of checking, but if that's all you got, you'll have to make do. (P.S. don't use Live View to test AF, as the AF technology used is different)