A used lens can be a smart way to expand your camera kit, but appearance alone cannot tell you whether it works properly. Take time to inspect the glass, test the focus and aperture, and look over the barrel and mount. If possible, bring a compatible camera and make a few test images. These checks help you spot problems before paying and give you clear questions to ask the seller.
Inspect the Glass Carefully
Remove both caps and examine the front and rear elements in bright, angled light. Small dust particles inside are common and may not affect images, but scratches, chips, haze, or fungus deserve closer attention. Look through the lens from both ends, rotating it gently to see whether marks change with the light.
Check for oily residue or a cloudy film, especially around the edges of the glass. Avoid touching optical surfaces. If you find a concern, ask the seller whether it appears in photographs and request a sample image taken with the lens. For a significant defect, compare the risk with the cost of professional servicing before deciding.
Test Focus Through Its Range
Turn the focus ring from its closest focusing distance to infinity and back. The movement should feel even, without grinding, sudden resistance, or loose sections. Manual focus should respond predictably, and autofocus should engage without repeated hunting or unusual noise when tested on a compatible camera.
Take test shots of a nearby subject and a distant one, using the viewfinder or camera display to confirm focus. Check focus at different points across the ring’s travel. For autofocus lenses, try both single-shot and continuous modes if available. A lens that focuses inconsistently may need adjustment or repair, so do not rely only on a quick demonstration.
Check Aperture Operation
Set the aperture to its widest setting, then move through the available values. On a lens with a manual aperture ring, check that each stop clicks or moves as expected. If the lens has an electronic aperture, test it on a compatible camera and confirm that the camera changes the setting and records the exposure correctly.
Look at the aperture blades while changing the setting, if the design allows. They should move cleanly and appear free of oil or damage. Some lenses keep the aperture open until the camera takes a picture, so that behavior can be normal. Take a few images at different aperture settings and review them for unexpected exposure changes or operating errors.
Review the Barrel and Mount
Inspect the lens body for dents, cracks, loose rings, and gaps that could suggest impact or poor repair. Check that zoom and focus rings do not wobble excessively, and extend or retract the barrel if the design requires it. Cosmetic scuffs are usually less important than damage that affects movement, alignment, or a secure fit.
Examine the mount for bent parts, damaged threads, corrosion, or worn electrical contacts. Confirm that the rear cap fits and that the lens locks onto your camera without force. Ask about the lens’s history, included caps, and return terms. A clear answer and a chance to test the lens can make the purchase more straightforward.
A careful inspection does not guarantee a used lens will never develop a problem, but it can reveal many issues before purchase. Test it on compatible equipment, take sample images, and ask direct questions about anything that seems unusual. If you are shopping locally, Newcastle Medium Format can help you discuss what to look for in a pre-owned lens.