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LENSES
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possible that the balance of favour will still rest with the first plate, but when placed 6 or 8 feet from the eye and viewed in a good light, it must be admitted by even the most ardent adherent to the older idea that a good portrait should be sharply defined, that although the picture loses somewhat in detail owing to diffusion, yet it certainly gains a good deal in general artistic value.
One of the most pleasing applications of the rapid portrait lens to other branches of photography is the production of pictures of town life by night.1
Wide-angle Lens. — Sometimes it is found when using an ordinary R. R. lens that it is impossible to place the camera sufficiently far from the object to obtain all that is desired on the plate. It may be that it is not possible to quite take in the whole height of a tall building or the whole width of some extended scene. Then it is that it becomes necessary to employ a wide-angle lens.
This diagram shows an ordinary form of R. R. wide-angle lens working at //16. This lens can be used with the smallest stop, so as to include angles up to nearly 100°. The front combination can be used by itself as a complete lens and then has about twice the focal length of the original compound lens.
The next diagram shows a special stigmatic lens of slightly greater focal length than the preceding. It works, however, much more rapidly, giving good definition at //6. On the other hand, the field is not so extended (about 85°), but each combination can be used as a
Fig. 43.
1 An excellent series of such pictures appeared in Photography and Focus, March 16th, 1909. These pictures were taken by means of a Dallmeyer 2B portrait lens at //3 3, by exposures of | to 4 or 5 seconds, according to subject and the kind of plate used.