Depending on how scrupulously one goes about things, a sharpness comparison of two lenses can end up being quite a hassle. One could compare the sharpness at multiple distances. One could, even when comparing a prime lens to a zoom, not only shoot at the same aperture but shoot photos with the prime at those apertures which the zoom is lacking and compare the results to the zoom’s largest aperture. I’ve done the latter, but I only tested at close range. A sharpness comparison at long range is coming in part two. Sometime when it has gotten a bit cooler and has therefore gotten easier to lug lenses as heavy as these two. 😉
Before we take a look at the photos, a few words regarding the test arrangement and modus operandi.
- The photos were shot from 1.5 meters or 4.92 feet away. The zoom lens was set to 135mm (-> largest aperture at that FL is f/5.6).
- A tripod was used as well as 10s self-timer. Zoom’s image stabilization was turned off. Just in case.
- With such long FLs and short distances it is not easy to align the camera perfectly parallel to the object being photographed. In order to do that one needs a lab and professional equipment for testing purposes. So please bear with me. 🙂
- The Sigma 135mm f/1.8 Art is always on the left.
- Lenses were focused at the part of the frame you see in the crops.
- You can find the full res photos on Flickr.
What is most striking is that the 135mm f/1.8 is either not as good between f/1.8 and f/2.8 as I have believed it to be or that I have done something wrong. Or the 100-400mm is simply better at its largest aperture than I have given it credit for? Since I work precisely and check everything when doing these tests, I can’t imagine where I could have done anything wrong. At f/4 the prime is sharper than the zoom at f/5.6 – but I would have expected it to be at f/2.8 or even at f/1.8 as well. In the range where I took phtoos at the same aperture with both lenses, the 135mm f/1.8 is always sharper, which excluding f/11 is to be expected. At f/11 I would have thought that both lenses would show a practically identical level of sharpness.