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August, 1927
AMERICAN CI N E M A T 0 G R APH E R
Seventeen
AMATEUR CINEMATOGRAPHY
(Continued from Page 10)
And a lens having a focal length of 2 meters, has a POWER of
1
= 0,5 DIOPTRIES
2
Expressing the Dioptric value as a formula, we have 1
D =
/ (in meters)
where D indicates Dioptre; and / the focal length of the lens.
As the meter is equal to 39.37 inches, if the focal length of the lens is given in inches, we must divide 39.37 by the given focal length thus 39.37
D =
/ (in inches)
As an example let us suppose a lens having a focal length of 2 inches.
We can find its POWER, by the Formula 39.37
D = = 19.69 DIOPTRIES
2
oi, as two inches equal meters 0.05080, by the Formula 1
D = = 19.69 DIOPTRIES
0.05080
The formulae used for finding the position of the Cardinal Points of a lens, require a too lengthy explanation for the space allotted to these articles.
We will therefore give the formulae, referring the reader to more complete works on the subject, for their thorough investigation.
Let us suppose a thick lens as in Fig 23
of which the value r0, r2, d and n, are known.
The values r0, r2 and d, may be easily obtained by actual measurements and the value n is always given by the manufacturer of the lens.
In such a lens,
r0 d
The distance V0 E' =
n (v0 -f r2 — d) -J d ( Continued on Page 18)
Progress of Photography, 1927
MEYER
KINO -PLASM AT
This is the latest contribution to Photography by the famous Dr. Rudolph, creator of the Tessar and Protar.
The enormous aperture makes practical, at last, successful filming, regardless of lighting conditions. Remarkable depth of focus for a lens of this speed. Especially adapted and recommended for shooting daylight interiors, and unfavorable lighting conditions. It is the only anastigmat free from focal differences with the various stops.
FOCAL LENGTHS from 20 mm. to 3 inches, can be fitted to all motion picture cameras.
Ask your dealer or write to
HUGO MEYER & CO., Inc., 105 West 40th St., New York City
Factory, Goerlitz, Germany A LENS FOR EVERY PURPOSE
Victor Milner, A. S. C, is in charge of photography for Emil Jannings' next picture for Paramount. The second American picture which Jannings is now making is entitled "Hitting For Heaven," and is being directed by Mauritz Stiller.
# # *
John Boyle, A. S. C, is photographing Mack Sennett's special feature, "The Romance of a Bathing Girl" and is directed by Alf Goulding. Johnny Burke, of vaudeville fame, is in the cast.
* * #
Joseph Brotherton, A. S. C, is shooting a Universal picture with Jack Daugherty under the title of "Haunted Island." Robert Hill is directing.
Edward Du Par, A. S. C, is chief cinematographer for the special Warner Brothers production, "The Jazz Singer." Alan Crosland is directing, with Al Jolson as the star. May McAvoy is featured.
* # *
Conrad Wells, A. S. C, is busily engaged shooting two Warner Brothers productions. The first is "A Sailor Sweetheart" with Louise Fazenda, and directed by Lloyd Bacon. The second production stars George Jessel in "Sailor Izzy Murphy," a sequel to "Private Izzy Murphy."