2. When you find a listing for a lens, determine as best as possible that it is compatible with your camera. Why travel across town to look at a lens just to discover that if you had asked, then you would have known it didn’t work with your camera? The listing may provide enough information to confirm the compatibility, but it’s probably a better idea to call the seller and discuss it with him or her. Ask what camera he or she has been using with the lens. You may want to go so far as to ask for the serial number, which you can check to authenticate when it was manufactured, and that it was legitimately manufactured.
3. If you’re confident the lens is compatible with your camera, then make arrangements to inspect the lens. Tell the seller that you will be bringing your camera and you plan to shoot a few frames with the lens and review them. You may even want to bring your laptop and download these test images to check them on a bigger screen.
4. When you’re able to inspect the lens, wrap your hand around it to determine if it feels solid and is still tightly constructed. The exterior of the lens should be clean. The focus ring should not rattle. Don’t be surprised if the rubber parts of the lens have scratches or white wear marks. That’s expected on a used lens, but use this condition as a negotiating point to lower the price.
5. Give the focus ring a complete turn and be conscious of how smooth and easy it operates. It shouldn’t hesitate or seem to be stuck. Do the same with the aperture ring, moving through the entire range of f-stops. It should also turn smoothly. Look through the lens to check that the aperture opens and closes as you change f-stops.
6. Next, inspect the front element by tilting it an angle, so a strong light reflects from it, revealing the lens coating. Look for a consistent finish and no marks scratches, swirls, or places where the coating has disappeared. A few small specks are no big deal, but they are more leverage for paying less than asked.
7. Move to the other end of the lens to check the mount. It will likely display some scratches, but these are expected. Inspect the rear lens element just as you did the front element. Reflect the light off the surface to see any marks, etc.
8. After inspecting the surface of the rear element, open the aperture to the widest aperture (smallest f-stop) and move the focus ring. The glass should move in and out. If it doesn’t, then you know you are holding a “lemon” lens. Show the problem to the seller and say goodbye.
9. Now, switch to the smallest aperture (largest f-stop). Look for a small pin on the back of the lens. It activates the aperture. The pin should move very freely, be very pliable, when you move it. Then, look through the lens to be sure the aperture is opening and closing. Open the aperture completely and release the pin. It should return to its original position quickly, with a snap. If it doesn’t react in this manner, then avoid the lens.
10. The next test is with the aperture ring set at the widest aperture. Position a bright light at the other end of the lens and look through it. You may spot some marks that look like spider webs. This is fungus inside the lens and you don’t want it. You’re buying a lens, not a terrarium. If you notice small dust particles, then don’t be concerned, but pay less than the asking price.
11. The final inspection point is a view through the front of the lens to look at the aperture blades, or diaphragm. Check that they are clean and still have a matte finish. Any shiny surfaces are likely to be a film of oil. This is another lens you shouldn’t buy.
12. Being sure you’re not buying a “lemon” lens from Craigslist is certainly time-consuming and you may have to travel considerable distance to inspect a lens, or more than one or two! An alternative to all that hassle and use of your valuable time is to rely on KEH.com, the world’s largest used camera dealer.
The people at KEH.com inspect and carefully grade every lens they sell, so you know the lens you buy is still a good piece of equipment. Plus, unlike a Craigslist seller, the lens you purchase from KEH.com is backed by a 6-month warranty.
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