Sunday, September 2, 2012

Staying in focus

Paseo del Prado
I shot these photos with a Canon 85mm f/1.8 EF USM autofocus lens that I bought for around $400 (naturally, the price went down by $50 after I bought mine). Here's how the B&H SuperStore describes the lens:
...a highly practical medium telephoto lens with superb delineation and portability. Images are sharp and clear at all apertures. Through computer simulations, the lens has been designed to give beautiful background blur. Since the front lens group does not rotate during focusing, special filter effects are not affected.
I like the tack-sharp images this lens produces. It is the fastest new lens I have (I have some faster vintage lenses - see "Lust for Lenses").
Fast lenses are the ones with the largest apertures. The aperture is the hole where the light comes in. The smaller the f-stop, the larger the aperture, so f/1.8 is fast.

What that means in practical terms is that you can shoot at a higher shutter speed in low light. You can also lower the ISO, which measures sensitivity to light. A low ISO - in the 100 or 200 range, for instance - means less grain.

I took this lens to Cuba this summer. I learned that shooting a fast lens can be tricky. The wide aperture makes it possible to shoot photos with an incredibly narrow depth of field of just an inch or two. But often that's too narrow. In a portrait, for instance, that means you might have one of your subject's eyes in focus, and the other out. Sometimes the photo looks fine, but not always.

Still, I love this lens, and I'm glad it now has a place in my backpack.

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