My wife and I recently visited the International Crane Foundation in Baraboo, Wis., where we saw large, long-legged and long-necked birds like the Grey Crowned Crane of Africa or the White-Naped Crane of Asia.

The center is the only place in the world where you can see all 15 crane species. Many have declining populations, and the ICF works worldwide to conserve cranes and their ecosystems.

The American Whooping Crane is one of the endangered species. Because of efforts like those at the ICF, the Whooping Crane has made a slow but steady recovery from a low of 21 birds in the wild in 1940 to close to 600 today. While we were there, the center’s pair of Whooping Cranes were preparing a nest, and on May 8 the ICF reported that the female laid 36 eggs, at least seven of which were determined to be fertile.

I’ve photographed Sandhill Cranes in the wild in Nebraska before and relied on telephoto lenses to get close-up photographs of the birds. I wasn’t sure what to expect at the ICF so I took both wide-angle and telephoto lenses. It turned out that the majority of the cranes were in medium-sized pens with netting above and wooden walls along the sides.

I could get within 18 inches of the front of the pens, but unfortunately between my camera and cranes was an ugly chain-link fence. I know of only two ways to eliminate the visible evidence of a chain-link fence from a photograph: create a shallow depth of field by using a long telephoto lens, or use wire-cutters. I was on vacation and using wire-cutters seemed like work, so I’ll explain the shallow depth-of-field trick.

Depth of field (DOF) defines an area in front of and behind a subject that appears in acceptable focus. Depth of field is determined by the focal length of the lens, the aperture and the camera-to-subject distance. Wide-angle lenses, small apertures, (f/22, f/16, etc.) and distant subjects will have great DOF. This is why your point-and-shoot pictures of distant scenes, on bright days, appear to have everything in focus.

Using a long telephoto lens, a large aperture (f/2.8, f/4) and being closer to your subject creates a shallow DOF. By using a 400mm telephoto lens at f/4.0 — the largest aperture on the lens — I knew I could reduce the field of relative sharpness and put more emphases on the cranes. As for the chain-link fence, I could pretty much eliminate it from my photographs as long as I kept my lens close to the chain-link and focused on a crane beyond the fence.

With such shallow depth-of-field, the telephoto lens rendered the chain-link as an almost unobtrusive blur. I had pretty good success, although if the cranes came right up to the fence, it would become impossible to eliminate visible evidence of the fence.

Try this technique yourself. Take a telephoto lens to a baseball game and position yourself behind the chain-link backstop in near alignment with the catcher and the pitcher. Place your lens on the fence with the center of your lens covering an opening of chain-link. Choose your largest aperture and focus on the pitcher. You should be able to blur out some evidence of the fence.

— Chief Photographer Mike Yoder can be reached at 832-7141. Check out more photos at ljworld.tumblr.com.