Depth of field in an image can sometimes be quite tricky to get right. Some images need an area to be in focus that is beyond the physical capabilities of the lens in use. Stopping down the aperture to achieve a greater depth of field comes at the significant cost of sharpness. Due to diffraction limitation, the sharpness of an image declines as you stop down past a certain point (around f8 in most lenses). With some images, even using a small aperture like f22 still doesn’t get the required amount of depth of field (this is particularly the case in close-up photography). In the past it was possible to achieve this extended depth of field using a Tilt/Shift lens taking advantage of something called the Scheimflug effect (basically tilting the lens so that the focus plane can effectively be extended). However, Tilt/Shift lenses are expensive, complicated and slow to use, and to top it off, are heavy. Thankfully digital photography allows us to achieve massive depth of field through something called ‘focus stacking’.

The number one reason why images fail, is focus (possibly it’s a tie between that and poor composition, but even the latter can be excused by some as art 😉). There’s that gut twisting realisation when you are going through the images from a shoot only to realise that the focus was out. What could have been fantastic, gets added to the trash pile. We now have blistering fast auto focus, face detection, dynamic tracking, 3D tracking, a gazillion focus points, micro-tuning (automatically calibrated on some cameras even) and more. You’d think that it would be as simple as pressing a button and shooting. But it’s not. Although we can get passably sharp results almost every shot, we still miss critical focus from time to time (if not more occasionally) and it is mind-numbingly frustrating!

There are a number of things we can do to try and improve focus when we are shooting, whether it’s shooting a landscape, a moving animal, or a close-up. I personally feel that correcting focus falls under these three broad categories of; Calibration, Settings and Technique.