In the preceding chapter some account has been given of the various types of lenses and their distinguishing characteristics, so that the reader is now in a position to decide on the lens he is going to purchase. Some additional remarks will, however, be of interest.

Opticians say that the very best lens a person can afford is the one that should be purchased. That is what any one would expect them to say in their own interests. To choose a lens in that way is absurd, and it is much more important to consider the kind of work you are likely to use it for. You can then select the cheapest lens which will do such work efficiently. There are many photographers in existence who have taken up photography simply as a means of artistic expression. The aim of many of these photographers is the production of those extremely blurred, featureless pictures which adorn (?) the walls of our chief exhibitions, and these photographers produce nothing else. I could instance one worker, who whilst he has a very expensive anastigmat, produces nothing but badly defined pictures from his exquisitely defined negatives. Such pictures may be artistic, but with that we are not concerned. We are only interested in the means of production. Pictures of this type can very readily be produced by the single non-achromatic lens which can be purchased for a few pence. Therefore it seems a sheer waste of money to spend pounds on an anastigmat.

If the single non-achromatic lens is used, all the tedious after-processes, such as interposing chiffon between the plate and the paper, or racking the lens forwards and backwards when enlarging, can be dispensed with.

Single Lenses

A single achromatic lens will fulfil the requirements of the landscape worker and portraitist. As illustrated by Fig. 20 these lenses give a distorted image, but, this will not be noticeable when photographing trees and the like. The image given by such a lens is very brilliant, since it has no air spaces, and if it is used as a narrow-angle lens, the field will be sufficiently flat to give good results without considerably reducing the aperture. This lens also may be considered as possessing considerable depth of field due to its curvature of field. The nearer an object is to the lens (which is focussed for a distant object) the nearer is the line in which the focal surface for that object cuts the plate, to the bottom of the plate. So that if the objects in the foreground are not very large, sharp focus may be obtained on both foreground and distance at a large aperture.

Rectilinear Doublets

For the worker who wishes to do general work, and to whom price is a consideration, a rapid rectilinear can be recommended. Such a lens is available for architecture, and other subjects in which distortion is not permissible. The definition is good at full aperture (usually F8) excepting at the edges of the plate. Good definition can be obtained all over the plate by slightly reducing the aperture; but, if a fairly long-focus lens is used, e.g. a 6 in. lens on a quarter plate, good definition will be obtained all over at full aperture. Rectilinears are made with an aperture of F5.8, and although such lenses are extremely useful in portraiture, where rapidity is essential, they are no better than the ordinary rectilinear for general work, owing to the amount of stopping down required to give good definition all over the plate. A rectilinear is composed of two symmetrical components, each of which can be used separately. Since the focal lengths of the components are equal, such a lens gives only two focal lengths.


The anastigmat will cover sharply the plate it is listed for at full aperture. When it is remembered that the full aperture for some of them is F3.5, and that the usual aperture is F6, it will be seen how very valuable they are to the photographer. A good anastigmat can now be obtained for very little more than the price asked for a new rapid rectilinear. The latter lens can, however, be obtained in a shutter at almost nominal prices second-hand. It must be remembered that the feature of the anastigmat is its ability to cover sharply at large apertures. When stopped down, it is no better than the ordinary rectilinear, so that if the worker is not going to do much hand-camera work where rapidity is essential he might very profitably buy a second-hand rectilinear. There is, however, one important difference between the anastigmat and rectilinear. An anastigmat listed for a quarter plate would probably cover sharply a 5 x 4 in. plate at full aperture, and a much larger plate at a small aperture. A rectilinear listed for a quarter plate would not cover sharply a much larger plate even with a small stop. It will be obvious that the former lens is of great use to the architectural photographer, who frequently has to use considerable rise of the camera front.

An anastigmat is also of great use when focussing in some poorly lit building, since at F6 the illumination of the focussing screen will be nearly twice as great as at F8 which is the usual aperture of the rectilinear. Moreover the photographer has only to stop down to secure depth of field, and not to secure good marginal definition. To the screen-plate colour photographer, a large-apertured anastigmat is of great use, and it is also indispensable to the copyist whose time is valuable. Now, there are many varieties of anastigmats. Some do not permit the components to be used separately. Others permit the use of the components, and since they are often very highly corrected and of unequal focal lengths, three good lenses are contained in one. Preference should be given to the latter type of lens, which will be found extremely useful.