- Ed Dozier
Lens Centering Tests
This is a basic test to perform before the return date expires on your new lens. Keep this test in mind if you ever accidentally give your lens a hard bump, too.
This idea comes from Roger Cicala at this link:
It’s cheap and easy to perform. The trick is to get your photos properly out-of-focus. I never thought I would give anybody that kind of advice. Also, you’ll want to under-expose your shot, since camera meters aren’t very smart about subjects like this.
Use notebook paper reinforcing rings stuck onto black construction paper. What you want is to get an idea of how the corners differ from the center and from each other. I fortunately don’t have any lenses with gross de-centering, so my shots show nice symmetric fuzzy circles.
According to Roger, there are very few lenses (some super-wides and mega-zooms) that might give a false-positive bad result.
It’s not important if your shots are out of focus in front of or behind the rings. What you do want is for the middle of the rings to still show just a little black.
The following shots demonstrate an 85mm lens and a 600mm lens test.
85mm lens f/1.4 Len Centering Chart properly out-of-focus
600mm f/6.3 All circles are boringly perfectly circular.
Look for circle characteristics that aren’t symmetrical; depending upon your lens, it’s expected that the corners won’t look exactly like the center, but each corner should demonstrate similar characteristics to the other corners.
Chart too out of focus. Centers have gone from black to white.
I prefer to shoot lenses wide-open for these tests, which will tend to magnify any lens faults.
There you have it. An easy, inexpensive lens-screening test. Remember this test when you buy your next lens to give it a quick once-over.
May your circles be symmetric.