This month’s blog will discuss the topic of focus in an outdoor landscape image. As in just about any photograph, attaining focus is extremely important. The difference between most landscape images and other genres like portraiture with regard to focus is that in landscape it’s usually desirable to have sharp focus from the foreground all the way to infinity. Whereas, with portraits, it’s often more impactful if the subject is in sharp focus while areas in front of and behind the subject are well out of focus. Viewer’s eyes are always drawn to the sharpest part of an image, which gives the photographer a way to separate the subject from the background and create more drama by using a narrow depth of focus. This is not to say that isolating a certain element of a landscape cannot be the goal of a landscape image as well, but generally the entire scene is going to contribute to the composition of a landscape.
Sometimes a SLIGHTLY out of focus foreground can be useful to gently ease viewers into a scene to give them a sense of place and context. These artistic decisions are entirely up to the photographer, but he or she needs to manage this important aspect of creating an image by having a complete grasp of the concept of depth of focus and how various factors will expand or contract that range. (SEE BELOW)
The factors that determine the range of focus in an image are the focal length of the lens, the lens aperture and the distance from the camera that’s being focused on. A wide-angle lens is going to have a greater depth of focus than a telephoto, and a small lens aperture (HIGHER F-Stop number) is also going to increase that range. The closer a subject is to the camera, the narrower the depth of focus will be as well, unless that distance is the HYPERFOCAL DISTANCE (which will be discussed later). These are the variables that determine an image’s focal depth, so as an example, a 17mm focal length lens combined with an aperture of F-22 focused about a third of the way into the scene will pretty much keep everything in focus. There are numerous resources, including phone apps that can give a photographer very precise calculations on what the depth of focus will be for any combination of these elements. My favorite iPhone app for this is “FocusFinder”, and it has a very user-friendly, intuitive interface to quickly see how changing any one of these elements will impact the focal range (AKA "Depth of Field") and it gives you immediate visual feedback. To fine tune the calculations, this app factors in the camera you’re using as well (including phone cameras).
The FocusFinder app (and many online resources) can also calculate the Hyperfocal Distance for any given lens focal length/lens aperture combination. Focusing on this exact distance away from the camera will give the highest possible range of focus for that configuration where everything will be in focus half-way back to the camera from that distance on into infinity. So for example if the hyperfocal distance is calculated to be 10 ft, setting focus at ten feet from the camera will make everything from a distance of 5 ft from the camera to infinity “acceptably sharp”. This is the best you’ll be able to do with those settings, but if you want everything to be “tack sharp” for everything in the scene, the only way to achieve that is with a technique known as “FOCUS STACKING”. This technique involves taking several frames focused at different distances from the camera and then combining them into one final image in postprocessing using Adobe Photoshop or other software. I’ll discuss this technique in next month’s blog.
THIS IS A SHORT VIDEO ON HOW TO USE THE FOCUS FINDER iPHONE APP TO CALCULATE HYPERFOCAL DISTANCE.
ABOVE FROM LEFT TO RIGHT AT A ONE TO ONE PIXEL RATIO, YOU CAN SEE ALL AREAS OF THIS PHOTO ARE SHARP.
Achieving sharpness in a landscape image is the product of many equipment-related factors, but wind and light levels in the scene will also dictate what aperture and shutter speed combinations you have to use in order to get a proper exposure. On a windy day, a slow shutter speed could result in motion blur in bushes, trees or grass (especially those closest to the camera), so changing to a larger aperture opening or a higher ISO setting will be necessary in order to stop the action. Compromises are always necessary out in the field, but knowing before-hand what your limitations are as well as how to use the available tools is the first step to making your best possible photo.