Pixiq

You should establish a goal before you test lenses yourself. As a landscape photographer, my goal is to find two lenses that give the best results at wide-angle, normal, and moderate telephoto focal lengths when using a fairly small aperture for great depth of field. It may not be feasible to test all of your lenses, but the reason to do so is to determine which are actually the best. You could be surprised. I was and ended up buying a new 70–300mm zoom lens.

There are two ways to test: (1) The complete do-it-yourself method or (2) a method that uses a lens testing kit (which is still a form of do-it-yourself, but with someone else’s methodology). The traits truest to a good tester include being thorough and methodical. We will be testing two variables: lens aperture and focal length.

I use both a resolution chart I downloaded from the web and a real-world subject that can challenge the lens. If you download a resolution chart, try to get a 16 x 20- inch black-and-white print made of it at a photo lab.

Finally, be sure to try your lenses with your favorite subjects, be they flowers, people, still lifes, or landscapes to make sure they pass both your formal tests and your real world shooting needs.

Lens Test Procedure

You can take test pictures in less than 30 minutes. Evaluating them on the computer for a single focal length will take a similar time. Comparing different lens tests on the computer may take an hour.

1. Mount your camera on a tripod.

2. Establish a position so that the subject nearly fills the viewfinder. If using a test chart, mount it on cardboard and position so it is parallel to the camera back without any glare reflecting from it.

3. If outdoors, make sure lighting is consistent and even. I prefer midday sunlight because it creates high contrast (shadow/highlight) borders that can challenge a lens. Choose a mostly front-lit scene, although moderate sidelighting is OK.

4. Record in a notebook the lens being tested and the picture series you will take. Number the shots. If you make a mistake, the file metadata should let you figure out the focal length and aperture used.

5. Set the camera to record RAW file format at the highest resolution.

6. Turn off the in-camera sharpening function (or set it to its lowest value).

7. Set the lowest ISO. Set the white balance to match the scene lighting.

8. Set the camera to Aperture mode.

9. Manually focus the lens on the center part of the subject and do not change the focus during the test. If you’re testing a zoom lens, test all the apertures at a single focal length and then move on to the next focal length and shoot another aperture series. You probably want to test a zoom at three to five focal lengths: the two extremes, the middle, and a focal length between the middle and each extreme.

10. Remove any protective filters and attach the lens hood.

11. Release the shutter via the self-timer, a remote, or a cable release. If your camera allows you to lock up the mirror, do so before taking the shot.

12. Shoot a blank frame as a later visual reference to indicate the start of the test series.

13. Take a test exposure with the lens set to its largest aperture and make sure the exposure is good. If you’re taking pictures on a sunny day with a large aperture (small f/number), your camera may not offer a shutter speed fast enough to create a good exposure. If you face that problem, you can test on a cloudy day, indoors with studio lighting, or use the next smallest aperture that gives a good exposure with your fastest shutter speed.

14. Take your series of test pictures, starting at the widest aperture and then increasing the aperture in whole stops, such as f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22.

15. Check the histogram to be sure the exposure is consistent as you take the pictures. The histogram shape and position should stay about the same (slight shift is OK). If it shifts significantly, retake the picture changing the shutter speed to keep an exposure consistent with the other shots in the test series.

16. When you’re done, shoot another blank frame to indicate the end of the series.

Redo steps 13–15 for each focal length of a zoom you’re testing.

Test Evaluation Procedure

1. Transfer the test shots to your computer and rename them with the lens manufacturer, focal length, and aperture used: example = Sigma30-f4.

2. Open the file shot at f/8, expecting (though not guaranteeing) that it may be the highest quality image to which you can compare other test images.

3. Next open the three or four RAW images shot at apertures wider than f/8 (images f/5.6, f/4, f/2.8).

4. If they don’t show similar contrasts and brightnesses, adjust them to be similar

5. Save each file as a tiff or psd file.

6. Now open the images in your image-processing program.

7. Enlarge the image shot at f/8 to fill your monitor. Examine it to get a general impression (including contrast if it’s an outdoor scene).

8. Enlarge the image to 100% and inspect it for sharpness and chromatic aberrations. Especially look at the corner detail and see how it compares to the center detail. If you photographed a resolution chart, note the smallest line pair that the lens can resolve.

9. Enlarge the image shot at the largest aperture (typically f/2.8 or f/4) to fill the monitor and examine it for vingetting, pincushioning, and barreling.

10. Enlarge that image to 100% and inspect as in step 8.

11. Next, postion the f/8 and f/2.8 (or f/4) images side by side and compare them at 100% for sharpness, resolution, and chromatic aberration.

12. Do this for all the test images, trying to identify the aperture that gives the sharpest results and fewest flaws. Note whether results at any apertures are so bad you should avoid them.

13. Make notes of your conclusions. Determine your lens’ strengths and weaknesses, which f/stops give the best results, and which should be avoided.

If you have a couple of lenses with similar or overlapping focal lengths, test and compare them against each other. The name of the game is to eliminate variables other than the lenses themselves and the attributes you are testing. By doing this you should be able to determine which is your ultimate lens. If you’re technically minded, you can buy a kit from imatest.com.