Keepan eye on this section for information on common photography terms and techniques explained so even I can understand them! You will also find examples of these techniques in my images.
Chiaroscuro (borrowed from the Italian for light and dark) is the term used to refer to the use of boldly contrasting light and shade to create three-dimensional modeling to enhance the illusion of depth on a two-dimensional piece of artwork or photograph. The use of this technique is common by artists (painters) as well as photographers. If light is coming in from one predetermined direction, then light and shadow will conform to a set of rules. A highlight will mark the point where the light is being reflected most directly. Where light hits the object less directly it increasingly registers a darker value or shade until you reach the point where the shadowed area of the form meets the lighted side. The use of this technique strengthens the illusion of depth of a two dimensional surface (or image).
Contre-jour (borrowed from the French 'against the day') is the term used to refer to the use of back-lighting and in photographs taken when the camera is pointing towards the main light source. Photographs taken 'contre-jour' will often show a bright halo of light around the subject. Fill in light provided by flash or reflector will often be needed to show detail in the subject which can also can be kept dark to create a silhouette effect. This technique can produce images with great impact and is suitable for portraits, still-life, landscapes and much more. Strong light shining towards the camera has a tendency to produce flare; you should normally use a lens hood to exclude light intruding from outside the pictures area.
Depth of field
In photography depth of field is the distance in front of and behind the subject which appears to be in focus. For any given lens setting there is only one point at which a subject is in sharp focus. Focus then falls off gradually on either side of that point creating a region in which the blurring is acceptable. This region is greater behind the point of focus than it is in front. Depth of field can be anywhere from a fraction of an millimetre as in macro (close-up) photography to virtually infinite as in some landscape photography where pretty much everything in the photograph can appear in focus.
Several factors determine the extent of depth of field; the lens aperture selected, the focal length of the lens being used and the distance of the subject from the camera/lens. The aperture controls the effective diameter of the lens opening. Reducing the aperture size increases the depth of field, increasing the aperture reduces depth of field. Aperture settings are adjusted to create variations in depth of field and are used by photographers to create a variety of special effects.
Lenses of short focal length (wide angle) have greater depth of field than long lenses (telephoto). To get technical for a moment, for any given lens, the depth of field increases as the distance to the point of focus increases up to the hyper focal distance. As the point of focus moves beyond the hyper focal distance the depth of field extends to infinity. The distance to the nearest point of acceptable clarity increases, so the total depth of field actually decreases. The greater the distance between the lens and the subject, the greater the depth of field, hence for close-up (macro) photography where the lens is very close to the subject, depth of field can be as little as a few millimetres, whereas for landscape photography, focus on distant mountains and the depth of field is extremely wide, even the stars in the sky will appear in focus.
At relatively close distances, for example in portraiture, it is crucial to focus on the 'right' point, usually the eyes, to ensure the most pleasing effect when using a relatively wide aperture to throw the background 'out-of-focus' to avoid it becoming a distraction.At relatively close distances, for example in portraiture, it is crucial to focus on the 'right' point, usually the eyes, to ensure the most pleasing effect when using a relatively wide aperture to throw the background 'out-of-focus' to avoid it becoming a distraction.
Depth of field is maximized by focusing the lens at the Hyper focal distance - the point of focus chosen to create a depth of field from infinity to a near point that is half of the Hyper focal distance. Although this may sound complicated it is not. For example if a lens is focused at infinity and the closest point of acceptable sharp focus is 10m from the camera/lens, the depth of field will extend from 10m to infinity. If now the lens is focused on a point 10m away (at the Hyper focal distance), the depth of field will still extend to infinity, but the nearest point of acceptable sharp focus will be 5m or half the Hyper focal distance thereby maximizing the depth of field.
It is possible to calculate the Hyper focal distance for any focal length of lens and at any aperture, however Hyper focal tables and charts are available from a variety of sources.
Bokeh is the transliteration of a Japanese word for "blur" and in photography is used to describe the subjective aesthetic quality of out-of-focus areas of an image projected by a camera lens. Some lenses are said to produce more pleasing out-of-focus areas that enhance the over-all quality of the image. Bokeh is a subjective quality that is difficult to quantify and is much debated.
In out-of-focus areas, each point of light appears as a disc. In some lenses, that disc seems uniformly illuminated, in others it seems brighter near the edge, for others it seems brighter near the centre. Some lenses show one kind of disc for out-of-focus points closer to the camera and a different kind for points further from the camera. An out of focus point of light with a more illuminated centre and a dimmer outer edge is considered to be more desirable than an evenly illuminated disc or one with brighter edges than centre.
The shape (and size) of the aperture is also known to have a great influence on bokeh. Mirror lenses produce a 'doughnut' bokeh that is typically considered as undesirable. Some lenses will show background light points as a many-sided shape rather than a circle. Generally lenses with more blades in the diaphragm tend to produce more 'round' bokeh. It is important to keep in mind that this only becomes noticeable when the lens is stopped down from its maximum aperture.