I often talk about how your camera sees the world differently than how your eyes and brain perceive things, and how you can use this creatively to make artistic photographs. Focus is one significant example; human eyes have a lot of depth of field, and as a result we typically perceive everything around us with seemingly perfect clarity from near to far (unless one has uncorrected vision problems, of course). A camera, however, can be used to selectively focus on only a specific object or part of an object—or, it can be used to achieve that perfect clarity from near to far, something I call "deep focus." Your choice of focal length, aperture, and distance from your subject can all have a profound impact on how sharply in focus objects appear, and you can use these technical decisions to create artistic images.
You basically have two choices for sharpness in your images. The first is selective focus, where only part of the image is rendered sharp, while the rest is rendered out-of-focus. Selective focus is achieved by using large apertures (such as f/2.8), which minimizes depth of field, which is the zone of apparent sharpness in front of and behind the focus point. With a very narrow depth of field, only part of the image will be in focus, and anything in front of or behind the focus point will appear blurry, with blurriness increasing as distance from the focus point increases. Selective focus deviates strongly from the way human beings generally perceive the world. The photo above of a cheetah is an example of selective focus. I used a wide aperture to ensure that the background behind the cheetah was rendered completely out of focus. The "creamy" blurriness of the background in this photos is typically considered ideal for selective focus images. Canon 5DIV, Canon 200-400mm lens with 1.4x extender, ISO 250, f/6.3, 1/250 second.
Your second choice is to use deep focus, where everything in the image is rendered tack sharp. Deep focus more closely approximates how humans typically perceive things, and is most commonly used in landscape photography. Deep focus can be achieved one of two ways. The first, traditional method of achieving deep focus is to use a small aperture to extend depth of field across the entire picture frame. This can be optimized by focusing on the hyperfocal point (or hyperfocal distance), which is between the near and far objects in a composition. Hyperfocal distance and depth of field can be challenging to understand and use practically, but luckily in the modern digital age we have a new, easier method for achieving deep focus called focus stacking, which is a processing technique that combines multiple images taken at different focus distances. The end result is a photo where everything appears to be in perfect sharp focus. I used focus stacking to capture the photo above, taken in a sandstone "sea cave" along the south shore of Lake Superior. Canon 5DSR, Canon 11-24mm lens, ISO 100, f/11, 0.5 seconds, focus stack blend.
When working with selective focus, you have to be choosy about what is in focus, and what isn't. As a general matter, you want to ensure that the most important part of the scene or subject is in focus. That usually means the part that is most engaging, interesting, or that best tells the story of the subject. For this photo of a Parson's chameleon in Madagascar, that "most interesting" part was the chameleon's bulging eye. Using a very shallow depth of field, I carefully focused on the eye, letting everything else go progressively blurry. Sony a7IV, Tamron 35-150mm lens, ISO 400, f/2.8, 1/800 second.
When getting creative with selective focus, what is out of focus is often as important as what is in focus. I often incorporate out-of-focus elements into my photographs, especially specular highlights and source points of light. For the above photo, I elevated the importance of the out-of-focus stuff to the highest degree by intentionally completely defocusing the lens, and then selecting a wide-open aperture to limit depth of field as much as possible. The colorful out-of-focus highlights create an artistic rendering of this Minneapolis street scene. Canon 5DIII, Tamron 15-30mm lens, ISO 400, f/2.8, 1/25 second.
With my wildlife photography, I often seek to put something between my lens and my subject so I can artistically incorporate out-of-focus elements to add depth and visual interest to my compositions. For this photo of a mountain gorilla in Rwanda, I chose a position where the gorilla was behind a stand of bamboo. Using a large aperture, the bamboo is rendered as blurry, framing the gorilla and telling a more interesting story. Canon 70D, Tamron 70-200mm lens, ISO 800, f/3.2, 1/400 second.
And for this photo of a satanic leaf-tailed gecko from Madagascar, I carefully selected a position that put a large specular highlight (a sunlit leaf in the forest) behind my subject. The out-of-focus orb creates a "halo" effect around the gecko, helping to emphasize it in the final composition. Sony a7IV, Tamron 150-500mm lens, ISO 800, f/6.7, 1/200 second.
The above photo is another example of creative use of out-of-focus specular highlights. While photographing this panther chameleon in Madagascar, I waited for the sun to emerge from behind the cloud, lighting the leaves in the forest and creating specular highlights. Using selective focus and a wide-open aperture, the highlights are rendered as colorful orbs. I carefully selected a position placing the best orbs in the background. Sony a7IV, Tamron 35-150mm lens, ISO 200, f/2.8, 1/250 second.
PRO Exclusive: Creative Focus Course
If you want to learn more about creative focus and the techniques discussed in this article, check out my Creative Focus Course, which is available exclusively to PRO Members. A PRO membership takes a deeper look at how compelling photos are made, and unlocks access to this course as well as a number of my other courses and tutorials.
My Creative Focus Course contains over an hour of discussion and demonstration of field and digital darkroom techniques that will help you better understand focus, depth of field, hyperfocal distance, focus stacking, and other related topics.