When photographers talk about lenses these days, it's mostly about the zooms. When the light's low, though, you can't beat a good fast fixed focal-length lens.

Twenty or thirty years ago if you wanted the sharpest possible photos, you avoided the zooms. That's changed now, and a good zoom rivals the fixed lenses in sharpness. Where the fixed lenses can beat the zooms is in their speed. And that's what I needed recently.

Some friends were getting married, and had asked if I'd do the photography. I was happy to oblige. The affair was going to be small, just a small group in a gazebo near a lake. At sunset. Or, more accurately, just past sunset. Which meant there wouldn't be much light for me to work with. Fortunately, I had just the lens for the job - the Nikkor 85mm f/1.4.

For most of my photography I prefer zooms because of their flexibility in range. It's great to be able to frame tighter or looser with just the twist of a wrist. And I have fast zooms, which are expensive but pay for themselves in helping me shoot in low light. My fast zooms, though, are f/2.8. Which means the f/1.4 85mm lens is two full stops faster. In photography, a "stop" is a full measure of light. One stop faster would let twice as much light into the camera, allowing the photographer to shoot at one full shutter speed faster. So that f/1.4 lens, being two stops faster, let me shoot at two shutter speeds faster. In low light that means the difference between getting a photo or a blur.

Using a Nikon D700, I could comfortably shoot around 1/100 second at ISO 3200 and make some beautiful images. Sure, some were blurry, as that's still a pretty slow shutter speed. But one great advantage to digital is that you can shoot LOTS of photos and just delete the bad ones (or in this case, blurry ones).

To wrap up the shoot, after the ceremony I took the couple to a nearby fountain. Shooting wide open, I used the f/1.4 aperture of the lens to blur the jets of water into a dreamy background for a kiss, while keeping the subjects in sharp focus. Which is why I often tell people to look at fast fixed lenses - that aperture lets you shoot faster shutter speeds and also gives you more control over depth of field (how the background looks).

Yes, I'm still a big fan of zoom lenses, and they're mainly what I shoot with. There will be times, though, where the best tool for the job is a fast fixed lens.