June 16 2013
One of the holy grails of photography is the quest for sharp photos where the edges of objects and details are clearly defined.
Photographers achieve this by using equipment suitable for the display method and applying photographic techniques that maximise their equipment’s inherent sharpness.
Size Does Matter
Expensive top end equipment is not necessary for sharp photos for standard 4”x6” prints or common email and web display sizes. Compact digital cameras, and even newer phone cameras, under favourable conditions produce photos that appear sharp in these display forms.
Using photos for large displays or in a high quality printing process, exposes the deficiencies of modest equipment, and the size of the camera’s digital sensor becomes a limiting factor. For displaying large high quality photos the choice is often a medium format cameras such as Pentax and Hasselblad, unfortunately these are expensive and are used mainly by established professional photographers.
The ubiquitous dSLR is a popular solution, their relatively compact digital sensors are large enough to produce quality photos and their popularity makes them more affordable than their larger cousins. The number of megapixels in the camera’s digital sensor is a factor in sharper photos, but not the only one. A larger sensor usually allows for larger individual pixels to collect more light for truer colours and less image noise, important contributors to taking sharp pictures.
The other advantage of dSLRs is the wide range of interchangeable lenses available, with varying prices and capabilities. This enables photographers to select a lens that provides the best sharpness, taking into account creative requirements for depth of field and focal length of the lens. Building a quality lens costs money and this results in the price difference between premium lenses from a manufacturer and their budget priced models. Photographers can analyse DxOMark lens tests to find the resolution or sharpness of a number of lenses.
All the best lenses and large high megapixel sensors are wasted if they are not used effectively. There are a number of ways for photographers to maximise the sharpness of photos taken using their existing gear.
Stabilise the Camera
The biggest enemy of sharpness is the camera moving while taking the photograph. This is not blurring caused by obvious camera movement, instead the result of these small camera movements is an impression of a lack of sharpness.
The best solution is to mount the camera on a sturdy tripod. Some photographers take the further steps of locking the moving reflex mirror in the up position after composing and before taking the picture. Another step is to use a remote shutter release so there is no chance of moving the camera while pressing the shutter button.
If a tripod is impractical then there are ways of reducing camera movement to improve the sharpness of photos. The first is to hold the camera body with two hands and rest the camera against your forehead then look through the viewfinder. This adds a third point of support, forming a human tripod. This is improved by resting on or leaning against a stable object, providing extra support for the human tripod. While these measures are helpful, using faster shutter speeds lessens the effect of any camera movement. Photographers should us faster shutter speeds with telephoto lenses than with wide angle lenses. Image stabilisation does not replace the need for the these techniques and is only part of the solution in the search for ultimate sharpness.
Choosing the aperture
The size of the lens aperture does more than controlling the amount of light passing through the lens. Aperture also influences the area in the photograph that appears in sharp focus, known as Depth Of Field.
Landscape photographers often want everything in a photograph presented sharply and maximise depth of field by using the smallest aperture (highest f number) for their lens.
Conversely portrait, or product photographers, often deliberately blur the background so it does not distract from the subject. They limit the depth of field by using the lens at its maximum aperture (lowest f number).
However, DxOMark lens tests reveal lenses are often sharper somewhere in the middle of their aperture range. Some of the theoretical increase in depth of field at smaller apertures is masked by the fall off in lens sharpness. Photographers can use the DxOMark tests to find the aperture range where their lenses are sharper and balance this against depth of field to maximise a photo’s sharpness.
Ensuring the area that appears in focus matches the photographers impression of the scene is more than pointing the camera and hoping the autofocus system will do the job.
The key is understanding the depth of field or distance from the closest point of focus to the furthest point of focus, known as the hyperfocal distance. This is a function of the distance to the subject, the focal length of the lens and the aperture setting.
The simple rule of thumb for scenic photography is to use a small aperture and focus on the horizon or to infinity for maximum sharpness and depth of field. Expert photographers use the hyperfocal distance to position the far edge of the Depth of Field on the horizon and make maximum use of the available area of focus.
Photographs can be made to appear sharper in digital post processing by increasing the local contrast between the edges of objects. This makes the transition stand out, but does not make the photograph any more precise.
Sharpness is only one attribute in a photograph and it should not be an end in itself. Using these techniques do have one intangible benefit slows the process down and gives photographers more opportunity to consider the composition before taking the photograph.