I'll illustrate these tips with some of my favorite images from one of my Alaska workshops with Hal Schmitt, who heads up the Light Photographic Workshops in Los Osos, California (lightworkshops.com). All the photographs in the article were taken with a Canon EOS 5D Mark III and a variety of Canon lenses: 15mm, 24-105mm, 70-200mm and 100-400mm. All images were processed in Adobe Photoshop CS5.
SHOOTING TECHNIQUESDetailed Subject. If you're looking for a sharp shot, you need a subject with details. For example, there are a lot of details in the feathers of the bald eagles in the photograph that opens this article. That's one reason why the image looks sharp. If I had been looking for an image to illustrate a soft photograph, I would have perhaps chosen to use a close-up of a rose petal taken in soft, low light.
Strong Contrast. Contrast—the difference between shadows and highlights in a photograph, as well as the difference in colors of the subject and the background—also can make a difference in the apparent sharpness of a photograph. What's more, photographs taken on overcast days tend to look softer than those taken on bright, sunny days.
Good Glass. Simply put, when it comes to choosing a lens, you get what you pay for. Invest in the best lens you can afford. That goes for teleconverters, too. Actually, that goes doubly for teleconverters. Go for the best. If you spend a few more bucks on a lens and teleconverter, you'll never question your decision.
Best Aperture. Many lenses are sharpest around ƒ/8. That said, I've seen sharp shots taken with a 70-200mm lens set at ƒ/2.8, as well as with an 85mm lens set at ƒ/1.4. In addition, due to diffraction, you'll get a sharper shot at ƒ/16 than you will at ƒ/22 or ƒ/32. Keep in mind that sharpness has nothing to do with depth of field. My advice is to test a lens at different apertures. A simple at-home test is to tape a newspaper to a wall, put your camera on a tripod, and take a series of exposures at different apertures. Also test for edge-to-edge sharpness. Some lenses produce images that are softer at the edges than they are in the middle of the frame.