About Lenses

Lenses are in fact the most important photographic equipment. They capture those beautiful moments of life onto photographic film to make them last for ever.

Lenses are especially important with smaller film formats. A 35mm negative needs to be enlarged by factor 69x to obtain a 20x30cm (8x12") print. A 6x6 medium format negative only needs an enlargement factor of 19x to get a print of the same size (at least mathematically, as 6x6 is a square format), a 4x5" large format negative only one of 5x. Thus excellent lenses are especially important in 35mm photography, as their optical errors will be multiplied very much at printing.

Generally spoken, there are prime lenses (lenses with only one fixed focal length) and zoom lenses (they offer a range of focal lengths). Zoom lenses were a development of and for 35mm, because the small negative size requires filling the frame - medium format and large format have much more allowance of cropping. Today, there are also medium format zoom lenses (in large format, there are so-called convertible lenses which offer two or three focal lengths by substituting lens groups; and plasmats which consist of many lens groups which you can combine to create several different focal lengths). Prime lenses offer better quality and are faster than comparable zoom lenses, but they are not as versatile. Cheap zoom lenses should always stopped down two stops whenever possible (say from f/4 to f/8) to minimise their optical errors. Medium f-stops always help to get the best out of a given lens (e.g. f/8 or f/11 in 35mm).

Lenses with a leaf (central) shutter (like for Hasselblad 6x6 5xx series or Rollei 6x6 or all large format or TLR or compact cameras) are generally spoken not as good as similar lenses for focal plane shutter cameras (like for Hasselblad 6x6 2xx series or virtually all 35mm SLR or rangefinder cameras), because the shutter within the lens limits the optical design. The same is valid for the modern image stabiliser resp. vibration reduction lenses Canon resp. Nikon offer.

Today, about all lenses are multi-coated. This means that several layers of coating are applied onto the lens surfaces so that flare is being reduced. This is especially important with modern zoom lenses, as they have so many lens elements and groups that flare would be enormous without coating. Older lenses are often single-coated, and lenses about before WWII are generally non-coated. But as these lenses don't have very many lens elements (often only doublets or triplets), this isn't that bad. A coated lens surface has a light transmission of about 65%, a single-coated one one of about 90%, and a multi-coated one one of 95-98%. So multi-coating is not much more than a marketing hype, and even an older non-coated lens can deliver excellent results if an appropriate lens shade is used - which is actually recommended with any lens - and extra attention is taken.

There are two definitions of a normal lens. The first one is that the focal length of a normal lens equals the diagonal of the film format (43mm in 35mm), the second that it equals the angle of view of the human eye. Over time, a focal length of 50mm has become commonly accepted as a normal lens. These lenses are cheap, but excellent. They are very versatile and lightweight, and some photographers use them exclusively.

Wide-angle lenses offer a larger angle of view than normal lenses. Their most common applications are landscape and press photography. They are rather prone to problems of sharpness, especially on the edges of the image, and good wide-angle lenses are a rather new development (also thanks to aspheric lenses). Wide-angle lenses of similar manufacturing quality are always better for rangefinder or large format cameras than for SLR cameras, because the mirror box of a SLR requires a retro-focus design due to the fact that the lens cannot protrude back into the camera body.

Telephoto lenses offer a smaller angle of view than normal lenses. Their most common applications are portrait, sports and wildlife/birds photography. They are rather prone to problems of sharpness due to different fraction of the colours, but today there are many good ones (also thanks to apochromatic and low-dispersion lenses).

A fisheye lens is a special form of wide-angle lens. It has a very short focal lenght, and it has a very obvious barrel distortion. There are two versions of fisheyes, full-frame (180° angle of view diagonally) and circle-frame (180° angle of view both horizontal and vertical). They are used for press photography where little room is available, and for special effects.

A shift lens is a lens with perspective correction. It is mostly a wide-angle lens, but you can shift the optical system so pretend being several meters above/below/left/right of where you really are. This is especially useful to avoid converging lines when photographing architecture or landscapes. Some shift lenses also offer a tilt feature with which you can change the angle of the level of depth-of-field. This is very useful for architecture again, but also for portraiture and product photography. Most large format cameras offer very generous shift and tilt effects through their characteristic movements.

A soft lens is a lens which has a built-in softening effect which can sometimes be regulated. This works via a special star-shaped diaphragm in most cases. Mostly telephoto lenses. They are very useful for portraiture, glamour, or wedding photography.

A macro lens is a lens which has been corrected for close-up photography, and which allows for scales of up to 1:1. They are mostly telephoto lenses, and often symmetrically designed (which reduces optical errors at 1:1). They are very useful for flowers, still-life, or portraiture.

A mirror lens is a lens which uses mirrors in addition to lenses. They are rather common for very long focal lengths, and normally not very fast, but relatively lightweight and small. Due to their optical design, out-of-focus elements of the image have a very strong circular form. Many people consider this very bad bokeh (a Japanese term describing the way in which out-of-focus elements are depicted), but these lenses are rather common if you need an inexpensive and lightweight long focal.