Let's be honest; modern Auto Focus systems are much faster than manual focus when it comes to many subjects. Don't get me wrong - I'm a big fan of manual focusing when the situation calls for it and time allows, but I'm also a firm believer in letting the camera and lens do the work in those situations where they may actually do a better job. In order for your equipment to get the job done right, though, there are a few steps you need to take and I'm going to lay those out for you here. Let's get right to it:
1. Stay within the sweet spot.
Try not to shoot at the extreme ends of the aperture range of your lens. Although the effects are more pronounced in inexpensive lenses, every lens will show more distortion, diffraction and aberration effects at the widest or narrowest aperture settings. Every lens is different, but most will have a "sweet spot" somewhere near the middle of the aperture range. Experiment with your lens to find it. A good place to start is often around f/8 to f/11. This is also a good idea when you're focusing manually.
2. Be still.
A surprising number of shots that appear to be out of focus are actually exhibiting motion blur from camera movement. In fact, this is one of the most common problems for novice photographers. Learning to shoot steady takes practice and discipline. Use your tripod or monopod when you can, along with a remote release. When you can't, keep your elbows tucked in against your body and support the camera correctly, with your left hand cradling the body and lens. Relax, exhale and then trip the shutter with a smooth, gentle motion.
3. Be careful when focusing and recomposing.
One of the most common and very useful ways to ensure focusing on the subject of a shot is to put an active AF sensor over the subject, depress the shutter halfway to lock the focus, then re-compose the shot. While this is a good method, it's important to realize that as you change the angle of the camera, you're moving away from that initial focal plane. If you're shooting with a wide aperture, even the slightest change in distance from the subject will be much more noticeable, too.
Try not to move your camera too much when using this method. It's also a good idea to learn to use back-button focusing if your camera offers this option (and most modern DSLRs do).
4. Sharpen in post.
Sharpening needs to be done in two stages for the best results: while shooting and during editing and sharpening for output. Start by capturing your images in the RAW format, because in-camera JPEG files will limit the amount of sharpening you can do in post without creating artifacts. It's also important to know that the final size of an image will determine how much sharpening you can do, so it's a good idea to sharpen as the last step, just prior to printing or converting to JPG for display.
5. Calibrate your lenses.
Your camera and lens work together to achieve focus and it's important to make sure they're set to deliver the best results. Like any other equipment, lenses vary and to get the best from an AF lens, your camera's AF system should be set to work with each specific lens. Higher-end DSLRs will allow you to store a correction profile for each AF lens you use, to ensure that you get repeatable focusing.
Most cameras have two types of focusing systems – Phase Detect AF and Contrast Detect AF. Phase Detect uses another sensor to achieve focus and Contrast Detect uses the image sensor to focus the lens. Modern mirrorless cameras use a combination of both systems on the actual sensor but DSLRs have two systems independently. Live View auto focus uses contrast detect on the sensor and is most accurate. Through the lens auto focus uses the Contrast Detect system. SpyderLENSCAL allows the user to tune the Contrast Detect autofocus system so it is as accurate as possible. AF fine-tuning is an adjustment of the Contrast Detect system and the LensCal helps in this adjustment)
There's an easy and efficient way to calibrate your camera and lens combinations. Datacolor's SpyderLENSCAL(tm) gives you an effective target to make the job of creating lens profiles through your camera’s auto focus adjustment quick and easy. What's even better is that it's surprisingly affordable. Check out the short video below to learn how it works, then follow the link at the end to improve the results you're getting from your AF lenses!