(Sere article on lenses in Part First.)
View lenses may be classed in two groups:
Single combination lenses and double combination lenses.
Single combination lenses are intended for producing pictures of inanimate objects, in the production of which the time of exposure is of minor importance. They are of greater focal length than the double, and, on account of their simple form, are less expensive.
The combination consists of a meniscus, composed of two lenses, one convergent, the other divergent. The two are cemented together, so that only two surfaces are presented to reflect light. This lens is well calculated for out-door work, but does not give such roundness of form nor such delicacy and finish as may be obtained by the double combination. But it has greater depth of focus, and, having but two reflexive surfaces, fits it peculiarly for views of foliage, and enables it to work into the green of the landscape more completely and vigorously.
The single lens is not free from distortion. The marginal rays are apt to give the barrel-shape figure to the view, but for landscapes this is practically of little or no consequence.
The smaller sizes of single lenses are more effective than the larger. They are quicker and have much less distortion, and when stopped very small have practically none.
The Double Combination is formed by reversing the single lens and making it the front lens of the double combination, and adding a similarly constructed achromatic lens to the rear. These lenses are indispensable for very rapid work and for work requiring straight lines. As the double combination is more perfectly corrected for spherical aberration, it is better adapted for architectural and other work not admitting of distortion. Of this class of lenses we would recommend which has a double achromatic combination for making instantaneous views, portraits groups, etc., and will meet all the requirements of those who do not care to incur the expense of a Dallmeyer or other first-class lens.
Anthony's Rapid Dry Plate Lens.
Of a higher class is which is the most perfect instrument at present known to the profession, and is almost universally used by professional out-door photographers and by all amateurs who care to produce the finest possible work. This lens might be considered indispensable for all work requiring an instantaneous exposure, as by means of the dry plate and the drop shutter some very remarkable pictures have been made of bodies in rapid motion.
The Platyscope Lens, which is a rectilinear or perfectly corrected lens of great working rapidity, and is well suited for all the requirements of the amateur; and as to price, it holds a middle place and next to the Dallheyer's Rapid Rectilinear Lens.
Dallheyer's Rapid Rectilinear Lens.