This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Advantages Of The Focal-Plane Shutter. The focal-plane shutter used on the "Reflex" allows the widest range of speed. Besides time exposures, it will give instantaneous exposures from five (5) seconds to 1-1200 of a second, and requires only a few seconds to change to these extremes. The ability of these shutters to make the fastest exposures has led many photographers to place the Reflex camera in a special field of usefulness. Their field, however, is far wider, and they should be used in every instance where accurate focusing on movable objects is required, immaterial if they move rapidly or slowly. The illustrations accompanying this article aptly explain this point. The picture of Major Delmar (See Illustration No. 44), who was going at the rate of 2.08 1/2 on a half-mile circular track when this plate was exposed, was made in the 1-1200 of a second, and is a typical example of the speed work of which these cameras are capable. The children on the swing (See Illustration No. 42), were photographed in 1-250 of a second, and this picture is here reproduced to illustrate the perfect control a Reflex camera offers when it becomes necessary to "divide" the focus. The full opening of the lens (a No. 4 Goerz Celor of 9 1/2" focus) was used, and it was thus required to carefully set the lens to the most advantageous focus. Besides this, the proper moment of exposure and the most satisfactory composition could be determined with the greatest facility and certainty.
Adapted To Interior Portraiture. The vivacious baby boy (See Illustration No. 43), required an exposure of 1-5 of a second only, but nevertheless moved sufficiently to make focusing right up to the instant of the exposure an absolute necessity. As this last named picture was obtained in a rather unusual way, we give illustrations of this device and describe more in detail how an ordinary ing, for which purpose an electrically controlled flashlight, charged with 10 grains of flash powder, was used. The shutter of the Reflex camera was opened to the full width of the plate, and wound up just enough to completely uncover it. The flashlight was placed in position and the circuit breaker attached to the release button of the Reflex.
Reflex camera can be used with perfect success in the studio and the living room.
Illustration No. 47 Diagram of Electric Connection for Reflex Camera. See Paragraph No. 563.
The camera was then focused in the usual manner and the exposure made, same as if daylight only was used. The electric contact is made just before the release button reaches the end of its course, thus releasing the shutter at the instant the flash is made. In this manner the child and the dog, together with the interior of the room, are produced by the flash, whereas the view outside the window is obtained by the daylight.