While on vacation last summer, I had the opportunity to borrow some “L” glass from a friend who rented it and then loaned it to me for a few hours. It was a Canon EF 24-70mm f/2.8L lens, which was most similar to my Canon EF-S 17-85 f/4-5.6 IS. As long as I had the opportunity to try it out, I thought I’d go ahead and set up a comparison test to satisfy my curiosity. I’d been wondering whether the extra cost of the “L” glass was worth it, or even really noticeable. You can find comments online about how the L glass is sharper, or produces better color or contrast, but I have never seen comparison shots that prove it. (If you know of any such comparison shots posted online, please post a comment with the URL.)

Anyway, I set up my tripod and framed an image with the L glass first, and set the focal length to about 70mm (zoomed all the way in). I focused on some particular petals in a flower box side-lit by early evening sunlight, and squeezed the remote trigger to take the picture. Then, I replaced the lens with my non-L glass, tried to eyeball the same framing as best I could, then focused on the same flower and squeezed off another shot.

Both shots were recorded in RAW mode in my Canon 30D, and exposed at f/8 at 1/60. When I opened them in Photoshop, I could definitely tell that something had changed between the two shots, but it mostly seemed to be differences in framing and camera position. (The L lens is noticeably heavier than the non-L lens, and it’s a bit longer, which gives a slightly different perspective on the scene.) But, was there a difference in sharpness? Not that I could see. Color saturation or contrast? Maybe, but not significantly, and any difference could have been attributable to the change in the sunlight over the few minutes between shots.

My conclusion is that I could not find any reason to spend the extra money on the L glass as long as a non-L equivalent was available. The difference in image quality would be lost on me, and I have a very discerning eye for detail. The exceptions, of course, would be where a particular focal length or maximum aperture was only available in an L version. But as long as there is a non-L lens available for the work I do, I’ll stick with the more affordable options. Again, I invite readers to post comments with links to any relevant comparisons between L and non-L lenses, especially if they demonstrate a significant difference.