This guide will show you how to test your new camera lens for the most common flaws, all without any specialized tools. Whether you’ve just picked up a new camera lens at retail or are considering buying one second-hand, knowing how to test and evaluate a lens can save you time and money.
It’s important to check any lens you receive, because even when it’s coming brand new from a reputable retailer, there can be anything from sample variation to damage from shipping. Things get even trickier when buying used – just like a used car, you rarely know exactly how the previous owner treated it.
The major potential issues include decentering, physical damage to the lens elements, sticky aperture blades, excessive dust between the elements, and issues with the zoom or focus mechanisms. All of these are pretty easy to check, and in today’s guide, I’ll show you how to find any issues early and easily.
Test your New Camera Lens for Decentering
The elements within the lens need to be centered to yield the best image quality. Decentered elements can cause a variety of image quality issues – most commonly, one portion of the picture appearing softer than the rest. There is no good workaround or fix for decentering, and even sending the lens off for repair is hit-or-miss. It’s best to test for decentering as soon as you get the lens, and return it if it’s a bad copy.
To be clear, all lenses are going to have slight variations from copy to copy, and this is nothing to worry about. Complex lenses, especially zooms, almost always have some minor decentering and sample variation issues. The important thing is to get a lens that performs within your needs.