In Part 2 of my review of the Tamron 150-600 f5.0-6.3 lens, I show the results of the controlled test I used to compare the Tamron lens to the Sigma 300-800, and Nikon 200-400 lenses. I used a 1951 USAF resolution chart test that I purchased from Edmund Scientific about 20 years ago. A check of their website revealed that they are still selling them. Some of the charts are quite expensive. I recommend the Resolving Power Chart for $35 at
or the Pocket 1951 USAF Optical Test Pattern for $6.00 at
The 1951 USAF resolution chart
There are a number of types of resolution charts available for testing lenses. I like the 1951 USAF chart because it is easy to quantify the results. If you want precision and you carefully follow the instructions, you can get actual line pairs/mm readings. But you have to be precise—with the lens at a set number of inches (depending upon focal length) from the chart and the camera positioned perfectly square to the chart. My method is much simpler and I think it gives me enough information.
The chart consists of a stepped series of three-bar patterns organized in an orderly progression of decreasing size. Each three-bar pattern, called an element, consists of three horizontal and three vertical bars. The elements are arranged in groups, with six elements in each group.
Once you’ve completed your test, you view the results on the computer, zoom in on the image and find the smallest element where you can still see separate horizontal and vertical bars. That is your level of resolution and can be quantified by Group/Element designation, ex Group 1/Element 5. My chart contains groups -2, -1, 0, 1, 2, 3 with elements 1-6 in each group. Group -2 begins in the lower right corner and the groups and elements progress in a clockwise direction from this outside lower right corner to the smaller interior groups and elements.
I mounted my Edmund’s test chart to a 20” by 30” piece of foamcore. I position each camera/lens combination at a distance such that the foamcore just fills the viewfinder frame, adjusting the camera position to make sure the borders of the foamcore are parallel to the viewfinder frame edges. This setup ensures that image magnification is the same for each lens tested and that the target is roughly square to the camera. I don’t feel that this method is precise enough for judging corner and edge sharpness, but, for my purposes, I’m looking at results in the central region of the chart.
I did this test in full sun and just tested wide open and 1 stop down apertures—to ensure fast shutter speeds. To eliminate all vibration concerns one should use flash. When I use flash, I set up the target in a darkened garage and position my long telephoto lens outside at the necessary distance. I use halogen work lights for focus, then shut them off to make the exposure with flash. Focus is achieved using Live View and manual focus or Live View’s contrast detection AF. By using Live View, you are eliminating any inaccuracies in the camera’s normal phase detection AF system, like the front-focus issue which occurred during the field test with my 200-400 and 1.4 x teleconverter.
For each test situation I shot five images using Live View manual focus and five images using Live View contrast detection AF. I then picked the sharpest image of each set of ten and scored it by Group/Element.
Results and Discussion:
Below are 200% views of my test shots along with my scores. Scoring is still somewhat subjective, because sometimes a test will come very close to resolving the next element lower. It should be noted that I am scoring resolution only. Some images are higher in contrast and that can increase the “apparent” sharpness of the image. I have found that lower contrast in an image can be compensated to a great extent in post-processing (adjusting contrast, clarity (local contrast), and sharpening.
All lens/aperture combinations scored the same—with the exception of the 200-400 TC14EII at f4.0, which was noticeably less sharp.
All the lenses tested were zooms,because I like the compositional flexibility of a zoom, especially when shooting from a blind. The first long telephotos I owned were fixed focal length: manual focus Nikon 400mm f3.5 and 600mm f4 lenses. The Nikon 400 f3.5 was, at the time, reported to be Nikon’s sharpest telephoto lens. My 600mm tested very close to the 4oo in sharpness. When I replaced the manual focus telephotos with the Nikon 200-400 and Sigma 300-800, the 200-400 tested similar to the 400 f3.5 while the Sigma 300-800 was sharper than the Nikon 600.
The Tamron 150-6oo impressed me a lot. It was easy to hand hold, sharp and fast to AF. I had no problems focusing on my dogs playing in the backyard. Speed of AF acquisition was not noticeably different than with the Nikon 200-400, Its VC (vibration compensation) was quieter than the version 1 200-400. All in all, it is a lens that I believe I will use a lot.
Tamron 150-600 at f6.3: Group 1/Element 6