We use the term macro photography when taking close-up images, but are we applying it correctly?
The macro setting
Tucked into the exposure mode dial or perhaps in the subject selection bar in a digital camera menu, there is often a flower symbol.
If you own an older Canon lens it may be found on the barrel, together with a number in metres or feet.
The flower is the international symbol for a close-up and the number is the nearest focus distance of the lens.
The measurement is that from the film or sensor image plane in the camera, not from the front rim of the lens, to the subject. The image plane is usually marked on the left of the top plate, but is not always present on digital cameras, and it only becomes important in technical work.
When set to this close-up mode, the tendency is for the camera to use a lens aperture to give shallow depth of field. This isolates the subject against a diffuse background since depth of field is limited in close-up anyway.
Lenses and kit designed for close working are often called macro, as in a macro zoom. However, the purist will point out that macro is really applied when the size of a subject’s image is bigger than the subject, up to 10x its size.
In photography, any lens that can focus closer than you might expect tends to be called macro. The label is often attached to zoom lenses, which are called zoom macro or macro zoom lenses.
A monofocal (or fixed focal length) lens that has the macro label will usually focus close enough for the subject and its image to be the same size. Yet zoom lenses fall short of that, as they focus mostly at about half size.
The size ratio between subject and image is termed the reproduction, or repro, scale, or given as a magnification factor.
Same size is a 1:1 repro scale, for example, and half size is 1:2. Just put the first figure over the second to give the fraction of image to subject size.
Rated as a magnification, 1:1 is 1x and 1:2 is 0.5x. For most close-ups, the actual repro scale or ‘x factor’ is far less important than the composition of the picture.
The reason zoom lenses do not focus down to 1:1 is that the optical corrections governing image quality are difficult to maintain when close in while at the same time maintaining them over the range of focal lengths.
In fact, they are rarely free of one error when at close quarters, which is curvilinear or drawing distortion. This is the bending or bowing of straight lines in the subject. It means that these lenses are not good at taking pictures of buildings or for copying documents, drawings and pictures.
However, this leaves the whole of the natural world wide open for taking subjects, both living and still.
A macro telephoto zoom at its top focal length is ideal for taking nature pictures.
It allows a close-up to be taken from a distance at which a live subject won’t become aware of you.
Macro monofocal lens
Once the photographer is hooked on close-ups, it is time to consider upgrading to a macro monofocal lens able to focus to 1:1.This opens up a further and fascinating field of opportunity in nature photography.
Also, since these lenses are well corrected for distortion, architecture and other linear subjects will be accurately rendered when shooting at middle and far distances, at which it remains well corrected.
The copying of documents, old photographs and so on can also be undertaken. Selective enlargement of a section of a shot taken at, say, 1:2 will give the impression of one at 1:1, but the quality of colour and detail will not be as good as from a 1:1 lens.
A plus point of close-up work is the fact a photographer has time to consider the lighting, camera angle and composition.
Such freedom is at its greatest in table-top photography. This is the equivalent of still life in painting – objects are chosen and arranged to satisfy the photographer’s creative skill. Overall, close-up photography is a fascinating genre which, once tried, usually becomes a lifetime pursuit.
Image: At 1:1 reproduction, the details of everyday objects take on new significance