This is a simplified list on the things to look for when evaluating the quality of a lens. The world of lenses can be a deep rabbit hole to dive into, but I put together this list as a primer on the various things to look for when picking out a lens. Either brand new or used. Especially used where there may not be a manufacture to back up the product with information or support. It's good to know what you're getting into and if there are issues with the lens, are these actually issues for you or are they acceptable compromises in the trade-off between price and quality?