Few months ago, we compared three Nikon 50mm lenses and examined center and corner sharpness. To complete the exercise, this time, we’ll compare three Canon lenses – Canon 50mm/1.4, Canon 50mm/2.5 macro, and a 17-50mm Tamron zoom XR DiII SP. The Tamron zoom is better and faster than the Canon 18-55mm kit zoom that was omitted from the comparison. For my type of shooting, I find also, that the 17-50mm range is more useful than 18-55mm.
All images were obtained on a bright, sunny day, at F8, and 1/1600s, and a APS-C format Canon T2i camera was mounted on a solid tripod. The images were not manipulated nor sharpened.
The first set of images shows the overall uncropped images (reduced to 720×480 size).
1. Canon 50mm/1.4 – ISO 200, F8.0, 1/1600s
2. Canon 50mm/2.5 – ISO 200, F8.0, 1/1600s
3. Tamron 17-50mm – ISO 200, F8.0, 1/1600s
The primes show better contrast and more vibrant colours than the zoom lens (notice the red chimneys and the reflection in the water). On the other hand, Tamron lets more light through at the same aperture. If you are going to print it in small size or use it just for Web, you won’t notice any difference in image quality, regardless of the lens used.
Next set of images shows a crop of the middle section (you can click on the images and see it in full 100% size).
1. Canon 50mm/1.4 – ISO 200, F8.0, 1/1600s
2. Canon 50mm/2.5 – ISO 200, F8.0, 1/1600s
3. Tamron 17-50mm – ISO 200, F8.0, 1/1600s
Both Canon primes are very sharp in the middle section (remember, this is output from a RAW, unsharpened image). As expected, the zoom lens is not quite as sharp, but again, printed at small to medium size or reduced to a web size, it is quite acceptable (you’ll need to view the samples at 100% to see the difference).
The last set of images shows the leftmost section in 100% crop
1. Canon 50mm/1.4 – ISO 200, F8.0, 1/1600s
2. Canon 50mm/2.5 – ISO 200, F8.0, 1/1600s
3. Tamron 17-50mm – ISO 200, F8.0, 1/1600s
Both Canon primes show excellent corner sharpness and some moire on the metal netting of the deck balcony. The 50mm/2.5 macro shows slight amount of green fringing along the vertical edges (noticeable on the two white beams under the roof), but that can be easily corrected in Lightroom). The Tamron zoom, as expected, is not quite as sharp, but due to the loss of knife-edge sharpness, it indirectly gets rid of the fringing, and moire on the balcony is also less pronounced.
Conclusion:
If you need the best quality, the 50mm/2.5 macro is hard to beat (it is also the least expensive of three tested lenses). In image quality almost indistinguishable from 50mm/1.4, and you get also the macro capability. Of course, if you need a fast lens in low-light situation or better isolation of the main subject, the 1.4 aperture will be the better choice. Tamron zoom is the longest and heaviest of the three, and not quite as sharp as the 50mm primes, but in good light and exposed at its sweet spot, it delivers good image quality and a useful range of focal lengths.
One more difference:
If you look carefully at the rightmost window in the cropped version in the last set of pictures, you’ll notice a startling difference. In the first two images, photographed with Canon prime lenses, the test subject sits straight and appears interested in his surroundings, whereas in the last photo he stopped cooperating and fell asleep.
advantica 
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