I've been a firm believer that upgrading one's gear usually doesn't improve one's photography. However, I recently picked up the Canon 85 f/1.8, and I must say, this lens has definitely improved my work. Why? Interestingly, it's due to more than the image quality. Yes, it's a great, sharp lens, but it's really not head-and-shoulders above some of my other lenses.
So if the image quality of the lens isn't leading to noticeably better images - what's changed? Inspiration. For a number of reasons, when I shoot with the 85 I feel inspired.
First, the focal length. I spent most of last year shooting with a 50mm, so the focal length is a little longer, and it inspires me to shoot from different perspectives.
Second, the feel. The size and weight of the 85 on a 5D feels just right to me. It's light enough to not wear me out after a full day of shooting, but it's also solid enough that it doesn't look or feel like a toy.
Third, the image quality. There's no denying, this is a sharp, impressive lens. It may not produce quite the background blur of the 85 f/1.2, but the image quality is still pretty awesome. If I nail the exposure, focus, and composition, I can be quite sure that the lens will do the rest.
So, my question is: Is there a particular lens that inspires you and, as a result, makes you a better photographer? If so, what lens, and why?