Do It Yourself Lens Testing
Lens testing can be as simple or complex as you want to make it.
If you prefer not to do any testing yourself, there are several printed and online sources for lens tests.
Online Lens Reviews
Another site with good lens reviews is Photozone. Photodo also has a set of lens tests. With their permission, I have published a summary of their test results on this site, including some lenses they have tested in the past that are no longer listed on their site.
Why Test Your Own Lenses?
As valuable as printed and online tests are, it's not quite the same as testing your own lenses. Although manufacturing consistency is generally good, occasionally a bad version of a good lens slips through. Some professional photographers used to buy 4 or 5 copies of the same exact model of lens, test them all, keep the best, and return the rest of a refund. Although not going to that extreme, I did buy a lens that seemed lacking in quality. I tested it against another lens I knew to be sharp, confirmed my suspicions, returned it, and bought another lens which I also tested. It was great.
Some photographers test their own lenses to answer any nagging questions they may have. Which of my lenses are the sharpest? Which apertures are
the best for each of my lenses? Which lens works best in demanding situations (like shooting into the sun)? Did I get a bad copy of a lens that is usually quite good in quality? Some people like to test their lenses
just for the fun of it. Whatever the reasons, there are several ways to check the quality of your own lenses.
The Brick Wall Test
Then view the whole photo on screen. Are the lines straight or do they bow in (pincushion distortion) or bow out (barrel distortion)? This is
where the brick wall test really shines. Compare different lenses at the same aperture or the same lens at different apertures.
The Newspaper Test
USAF Lens Testing
The most rigorous do it yourself lens testing that is readily available is to do lens testing with a USAF Lens Testing Chart. All of the details are at
the USAF lens testing page.
Flare, Ghosting, and Color Fringing
To check for flare, pick a clear, blue sky day with no haze. Hold up your hand at arm's length and hide the sun behind your thumb. If you see blue sky around the edges of your thumb, you have the right kind of day. If the sky around your thumb is bright and hazy, it isn't the right kind of day.
Take a picture with the sun in the middle of the frame (meter for blue sky away from the sun). Try different apertures. Then take more pictures with the sun farther and farther away from the center of the frame (again with different apertures) until the sun is at the edge of the frame. You may see one or more ghost images of the sun in the photos. This isn't unusual.
If the overall look of the image is soft or hazy, you have flare. Take a picture with the sun in the corner of the frame. Then take the same picture but block the sun with your hand so that no direct sunlight hits the lens (you will see your hand in the photo). If the second photo looks crisper, more defined, and with better color, the first photo is suffering from flare (kind of like driving into the sun with a dirty windshield as compared to a clean windshield).
Facing the sun, photograph a tree without leaves in the winter (or a dead tree in the summer) and hide the sun behind the trunk of the tree (use
different apertures). Or photograph a power pole with a lot of power lines and hide the sun behind the pole. Look at the edges of the small branches (or the power lines) and see if they have colored edges (often blue or
purple). This is color fringing. Some lenses are worse than others. Color fringing can be corrected with the right kind of software.
What Results Should You Expect?
Wide angle zoom lenses are usually sharpest and the medium and long end of their focal length range. At 10-22mm zoom lens will probably be sharpest at 15 and 22mm and less sharp at 10mm.
Some lenses are the exception to the rule. A little testing will show you how your lenses fit into the general scheme of things.
When it comes to ghosting, flare and color fringing, lenses vary quite a bit. Zoom lenses are usually worse than prime lenses due to their complex designs. There are exceptions. Some lenses do quite well when shooting toward the sun, and some don't. Testing will tell you which of your lenses does the best job in demanding circumstances. For example, if your 24-105mm lens has a lot of flare at 30-40mm, and your 17-40mm lens has minimal flare at 30-40mm, whenever you shoot toward the sun in that focal length range, use the 17-40mm lens.
Copyright © Jim Doty, Jr. All rights reserved.