By Sara Goodnick
Camera lenses produced before the digital age may still be in mint condition, but you might want to consider replacing them anyway. Here’s why. The newer lenses were designed specifically for capture by the digital sensor which is completely different physically and chemically from a film plane. To optimize this difference in sharpness and color capture you will probably need to upgrade.
Perhaps going to your local camera store and asking to test one of their lenses is an option. If not, rental through one of the various lens and camera rental companies will give you a feel for whether you should upgrade.
If you purchase a new lens, or want to test your old ones, there is a great tool available for free! It’s a downloadable lens test target, produced by B&H Photo Video, and available to anyone. The only problem is that it is almost impossible to find on their website. I asked them and they sent me the link: https://static.bhphotovideo.com/explora/sites/default/files/bandh-test-target.jpg
I downloaded it and took it to Costco to be printed as a 20×30 mat print. It came rolled up like a poster, but some photo mount spray and a piece of white foam core allowed me to mount it and hang or prop up for shooting my lens tests.
First set up the mounted target in in an area of even light. Most do not have a portrait studio or lights, so try to find a north light from a window in a room, a well lit room, or look for open shade outdoors (however, wind will be a problem there, so secure it well). You can check for eveness of the light by setting your camera for the perfect exposure using the best combination of shutter speed, aperture, and ISO, then use the camera’s meter reading to check both ends, the top, the bottom, and the middle to see if any parts are under or over-exposed by checking the exposure graph in the viewfinder or on top of the camera. Of course, an independent light meter is ideal. Get it all as even as possible, but if that isn’t possible, just plan to photograph the part that is most evenly lit.
Make a plan on what lenses you plan to test, and at which focal lengths and apertures. Also plan and mark on the ground at which distances you wish to test each lens. Be very methodical and it will help later. You could make these notes on individual pieces of paper and photograph each notation as you work by photographing it before each test.
For instance, if I want to test my 70-200mm Nikkor 2.8 lens this is what I might do.
Set distances of the closest distance it will focus zoomed in, at its longest focal length as listed on the lens barrel (200mm at 5 ft in this case), 10 ft, and as far back as I can and still fill the frame with the test target. At the closest distances, only a part of the target may be visible, but I will choose to photograph the part that has the most detail and set up the camera on the tripod there. Remember to use the cable or remote release, or mirror lockup. I will photograph the target at the lens’s largest aperture (f/2.8 for this lens), several middle apertures such as f/5.6, f/8, and f/11, and then f/16 and f/22.
Repeat this with the different focal lengths you want to test. I might go for one set at 200mm, one at 135mm, and the last one zoomed in to 70mm.
Then repeat this at the various distances from the target you have measured out for each lens you want to test. Lenses with variable apertures, i.e., those whose apertures will change when you change focal lengths will be a little more complicated in that you will have to take note as to what their limits are at each focal length.
At the smallest and largest apertures, you may find the need to add more light. If you cannot actually add more light itself, go to a higher ISO unless it takes you into an unacceptable noise level. Or you could begin with your largest aperture and lowest ISO. That will not affect the sharpness of the lens, and it is better if you can see the target!
Download this these images into your computer, label them with any info not already in their metadata, and compare their sharpness especially on the edges, and particularly at the smallest and largest apertures. You will learn a lot about your lenses this way, and photography in general.
It’s not nearly as much fun as going out and photographing your favorite subjects, but the knowledge you will gain will improve your future image captures!
Sara Goodnick is a Volunteer Photo Guide with Arizona Highways PhotoScapes