When I started my research to buy a “something wider than 50mm” I came across several options. From Canon, Sigma and Tamron. I really liked the idea of a 28mm f/1.8, but several reviews called it “unusable” on apertures faster than f/2.8 (meaning, the borders of the lens sucked…).
If I can recall, Ansel Adams used lenses made 60 years ago, before all the efforts in lens sharpness and aberration corrections brought by digital sensors had been made. I guess no soul on earth would dare call his pictures “unusable” because of the lens he used. How in the name of large aperture and rounded diaphragm blades would someone call a lens made nowadays “unusable”?
Of course I started searching for image samples and results from resolution, aberration and vigneting tests. The outcome was just as I expected: it`s a great lens, with good resolution on the center and borders. Surely, as every fast lens, the borders are substantially soft when fully opened.
I guess I only realized the real issue after buying and using the Sigma 50mm f/1.4. As I already stated here, the internet “screamed” that this lens had autofocus issues, that it`s results were “unusable” for “serious work”. Well, as I find out, it`s a great lens with focus shift caused by residual spherical aberrations. It had nothing to do with the auto-focus motor or with poor design by Sigma. Canon 50mm f/1.2L, a $1,5K lens, has the same issue (as well as most of the normal-wide fast lens).
I`ve come to realize that the issue is not the equipment, but the folks using it. Thankfully, nowadays, a normal guy like me can buy such a fast glass like the Sigma for under $400, misuse it, and complain all over the internet about how bad it is when focusing, how soft it is wide open, and ultimately, how unusable it`s results are.
The Equipment Mermaid sings to beginners the song of the ultimate photo with the fastest glass. One just need buy it and collect astonishing pictures. The horde of credit card-happy amateurs then buy fast glass (being the most common the Canon 50mm f/1.4, Canon 50mm f/1.2L, Canon 85mm f/1.4L, and mostly anything below f/2.8). Unfortunately, most of them end up frustrated with missed focus pictures and inconstant resolution trough the frame. All that not to mention strong vignette and color bokeh (also known as Transverse Chromatic Aberration) when used fully opened.
From all that, I managed to learn two lessons:
I try to learn as much as I can about my equipment or the kind of equipment I intent to buy. If you want to buy a telephoto lens, learn about it! Search online about the typical strong and weak points of its design and operation. Once I read a review comparing the Canon 600mm f/4 and the Canon 500mm f/4. One costs US$ 12K and the other US$ 10K. By that you can already assume that the choice among them is not based on price. The first one weights 5.4Kg and the second 3.9Kg. There you go. Even the 600mm having a clear advantage in reach, you can probably figure the strain of carrying a 5.4kg lens around all day.
Secondly and most important: read all the reviews you want to, but in the end its paramount to make the choice based on raw test data and pictures taken with the lens. The raw data (MTF graphs, vigneting, distortion tests etc.) enables you to infer the objective quality of the lens. Once you`ve done that, looking at multiple pictures taken with it lets you know if those objective factors translate themselves into images if the subjective character of the lens is pleasing for you.
I`ve learned that lots of websites provide “in depth” reviews of photographic gear. They evaluate the objective factors of the equipment and the look and feel of the lens. From what I`ve learned about photography (and its very little compared to what`s out there) no graph can tell if a lens is capable of making good images and no photography cares if it was shot with a “beautiful all metal body” lens.