Camera lenses should be pristine for the highest image quality.
Inspecting a used lens for damage or other problems is a required part of purchasing lenses. The price of a lens is dependent on the model and its condition. As a lens' condition decreases from excellence, its price should also decrease. Checking a lens involves inspecting each element. If a problem exists, it is up to the buyer to determine the seriousness of it. Some problems are only cosmetic, while others affect lens performance.
Instructions
1. Check the lens body for any damage. Some damage may be purely cosmetic, such as scuffs, while other damage may affect the performance, such as a broken barrel.
2. Rotate both the focus ring and the zoom ring to ensure that each rotates smoothly and to each extreme.
3. Look at the outer lens elements for any scratches, chips, scuffs, dust, mold or dirt. Any marks are undesirable and some may be more prominent than others. A small amount of dust inside the lens may be less important than a scratch in the middle of a lens.
4. Take several photos with the lens. Ensure the auto focus works effectively. Shoot photos both zoomed in and zoomed out, and at both extremes of the focus range.
5. Load the images onto a computer and view them at full screen. Inspect the subjects for sharpness. This measurement is relative to the viewer, but should be at an acceptable level.
6. Inspect the photos for chromatic aberration, which is the slight separation of colors. This most often occurs along the edges and is caused by light of different wavelengths following slightly different paths through the lens.
7. Inspect the photos for distortion, which is a slight round warping. This is most often seen with straight edges, such as tile. If present, the straight lines will appear slightly bowed instead of parallel.
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