will completely fill the bill. This lens consists of two cemented
combinations, each composed of a deep meniscus crown and a deep
concavo-convex flint glass lens.
Unlike other lenses of this class the dense refracting medium--the
flint--is made to occupy the external position in both combinations,
and though both are deep menisci externally, and of nearly the same
focal lengths, the front combination is of larger diameter and
greater curvature than the back, and between the two, dividing the
space in the proportion of their respective diameters, is placed the
revolving diaphragm, with graduated openings, the largest of which
is F. 15.
An important characteristic of this instrument, besides the method
of achromatization, is the thinness of the lenses, thus offering
less obstruction to the passage of the light, constituting these
lenses the quickest acting of their kind.
The outfit, which includes a Dallmeyer wide angle and a Dallmeyer
rapid rectilinear, may be said to be prepared to do all work within
the range of photography.
Every outfit should include a piece of fine, soft chamois [p162]
skin for cleaning the lenses; it will often be found that moisture
and dust obscure the image in the ground glass; when such is the
case the lenses should be unscrewed and carefully cleaned with the
chamois. And when carrying, it would be well to wrap each lens in a
piece of chamois. Lenses thus carefully kept will repay the trouble
in fine, clear and incisive work.
[Illustration: FIG. 1.]
[Illustration: FIG. 2.]
[Illustration: THE FAIRY TRIPOD]