Learn to focus like a pro
Independent of lens quality, poor focussing technique will always prevent maximum sharpness.
As photographers we are always striving for the ultimate sharpness and image quality. We invest heavily in lenses and ultra-high resolution cameras in order to achieve this, often spending thousands on professional grade optics. However, regardless of how precisely ground the glass elements in your lens are, or how many pixels your camera sensor possesses, sharpness can never be a certainty with bad focussing technique. As good as modern AF systems are, sometimes it is best to take back some control and dictate how and where your lens focusses. Here are some quick tips for improving your focus.
Move your AF point
While it can be a very effective way of rapidly focussing and composing, the focus-recompose technique fails to work at very wide apertures, as the focussed area is so narrow and may not cover your subject when moved. The technique works on the premise that all areas of your subject are within the same focal plane, so when you recompose your shot, this plane is tilted relative to the subject. At f/2.8 and wider, move the AF point in your viewfinder instead, as this will allow you to autofocus an area of your subject after arranging the final composition.
Assign focussing to your camera’s AF On (AF-L) button for locked focus, so that you don’t accidentally re-focus when lifting and re applying pressure to the shutter button, between images. This can be done using the custom function menu on your rear LCD, where you can chose which functions are controlled by each button on your camera body. While it may seem like an unfamiliar way of focussing, you will quickly fall into step with it and will likely find you introduce less vibration into your shot through camera shake.
Zoom in using Live View
The best way to ensure focus is to zoom in while still in-the-field, so you can re-shoot an image if you find your photo lack the requried detail. Assign one-touch 100% magnification to your zoom button from your camera’s menu, for rapid sharpness assessment. Additionally, if present on your camera model, activate focus peaking to assist with accurate focussing
The cross-type advantage
Cross-type AF points are more accurate than standard points, as they calculate focus on both vertical and horizontal axes. If your camera doesn’t feature all cross-type points, use the centre point only for greater precision, or alternatively, choose a custom function which allows only X-type points to be displayed in the viewfinder.
Use DOF preview
This feature is becoming decreasingly common on digital cameras, but the depth-of-field preview button is still of great benefit. To quickly assess depth-of-field at your chosen aperture, look through the viewfinder and press the DOF preview button, to stop down the aperture and reveal how much focus fall-off will occur