TRY ADVANCED TECHNIQUES
Follow these tips to squeeze a little extra sharpness from your images in tricky situations
Sometimes, if you have very close foreground interest, you need to be a little more precise than double-distance focusing allows. For every combination of focal length and aperture, there is one focusing distance that generates maximum depth of field – the hyperfocal distance. The calculations are quite complex, but fortunately there are many published charts and apps that show the hyperfocal distance for almost any combination. So for example, if you are shooting with a full-frame camera at 28mm f11, your app will tell you that the hyperfocal distance is ten feet; find an object at that distance and focus on it. As depth of field extends from half the hyperfocal distance to infinity, everything from five feet will be sharp.
Be careful not to overuse the hyperfocal distance, however. It’s only necessary when you have close foreground interest. If there is nothing close to the camera, you don’t need to prioritise sharpness in the foreground, so can focus further in – your background will be sharper as a result.
Sometimes, even the hyperfocal distance will not generate enough depth of field without stopping the lens down to its minimum aperture, which will soften the image due to the effects of diffraction. One solution is to use a tilt-shift lens. With a tilt-shift it is possible to tilt the plane of focus, creating extremely extensive depth of field without the need to stop the lens down. There are disadvantages, however: tilt-shifts are expensive, always prime lenses and manual focus only.
Focus stacking is a technique that can be used with any lens and also enables you to shoot using the lens’s ‘sweet spot’. It is the technique of blending several images that have been focused at different points, to give a single image that contains the sharpest parts of each image and is therefore sharp from foreground to background. It is a relatively straightforward technique and several cameras offer it as an automated function. Dedicated software is available to blend images, but this can also be done in Photoshop.