My parents bought me a new lens for my camera as a graduation gift. It's the Canon EF 300mm f/4L IS USM and it rules. It's my first pro-grade lens, and I am already loving it. At 300mm, it matches the highest focal length I had at my disposal (a 100-300mm f/4.5-5.6) so I did some quick comparison tests. Bear in mind that these are not scientific in any way and, as lens quality tests go, they are mostly crap. But you'll get the basic idea. First, the reference frame:

New lens, f/4, 0.3s. Distance of ~25'.

I chose this scene because there was a lot of small detail and it was across the longest room in the house. I suppose I could have gone through the trouble of moving the lamp... but... bite me. And no comments about my taste in movies, though if you can identify all of them from this image you win a prize [Nina, Robin, and Mikki not eligible].

So the first thing to look at was how the lenses compare optically. I took the same image (same settings) with both lenses and now I compare a small portion of each (shown at full resolution):

Top: old lens, f/4.5, 0.2s Bottom: new lens, f/4.5, 0.2s

Note that this is a very low-light shot so the autofocus might not be spot-on, but clearly the new lens is considerably sharper. This really isn't a composition where the superior quality of the new lens will make itself maximally apparent; the DVD rack is not normal to the axis of the lens and I made no attempt to ensure that the focus points were the same (and this sub-frame likely does not contain the most in-focus region). Despite this, the new lens frame is much sharper. I'll try to set up a more controlled test shot sometime, and hopefully one that will stress the glass a bit more.

Next on the hit parade, image stabalization. This is my first lens with IS. Here's a comparison of similar hand-held shots with the same settings, but with the new lens' IS enabled:

Top: old lens, f/4.5, 0.2s, hand-held Bottom: new lens, f/4.5, 0.2s, hand-held w/ IS

Now 1/5 of a second is pushing the limits of what I can hold steady. I was really bracing my arm against my side as steadily as I could. Still, shake from my heartbeat was moving the lenses. I'm impressed. A full-sized look at the stabalized shot does show some motion, but not very much. It's clear enough that you can read the finest print on the DVD spines.

In conclusion... the new lens rocks, I can't wait to shoot birds and stars with it. Thanks Mom & Dad!