|This is what photography is all about: lens testing! Good news: As this photo demonstrates, the Olympus 25 f1.8 is an excellent lens. Bad news: I need a new vacuum cleaner. (View at 100% to see why.)|
There are four ways to test a lens.
- Look at the price you paid for it. If you paid over US $600, it's a good lens. Over $800, it's a very good lens. Below $300, it's okay. Between $300 and $600 is a gray area and you might have to go one of the more advanced tests that follow.
- Look it up on DxO Mark. They'll tell you if it's any good or not. Favored by the pros!
- Obtain or make for yourself a test chart, and try to replicate DxO Mark-style tests, taking measurements. If you can't find a chart, a brick wall will also work. Be sure to view all the photos only at 100% or you might miss something important. (The popularity of this test keeps the makers of tripods in business.)
- Take a number of photos with the lens: different subjects, different shooting situations and types of light. Look at the photos on a good computer display, or better yet, make prints. If you have a similar lens or lenses, make comparisons based on various photos. Does the lens seem to do what you want it to do?
Test #3 will help you find defects in the lens. In fact, if you do it right, it's nearly guaranteed to find defects. On the up side, once you find the defects you went looking for, you'll have the satisfaction of knowing that you have incredibly high standards.
Test #4 is deprecated in nearly every internet forum, for several reasons. First, it's not scientific. Second, in order to answer the question "Does the lens do what I want it to do?" you have to know what you want it to do, and that's not covered in this lesson. And third, because there's too high a risk that you'll accidentally take a photo that you really like, which will only lead to unhappiness, since you know from test #3 that the lens is crap and you have to return it.
Originally posted 24 June 2014 over at DPReview, in response to a question about how to test a lens.