740 NOTES, CASES, I N S T R U M E N T S

-:Ibid., 1954, ν. 6, p. 5728. 4. -5. Holmes, G.: Observations on ocular palsies. Brit. M. J., 2.1165, 1931. 6. Walsh, F. B.: Clinical Neuro-ophthalmology. Baltimore, Williams & Wilkins, 1947, p. 306.

A F O C U S I N G A T T A C H M E N T F O R C L O S E - U P P H O T O G R A P H Y

ALFRED A . NISBET, M.D. San Antonio, Texas

When taking pictures o f the eye at close range, the depth of field is quite limited. Most cameras, except those using ground-glass focusing, depend upon fixed focus framing devices which are placed in the or­bital area to be photographed with more hope than accuracy. A s a result, many of the mon­ocular photographs have the cilia in sharp focus when it was an iris lesion that should have been clear. Lateral pictures of the eye are particularly difficult when frames are used. There is a definite need for an accurate means of getting a lesion into sharp focus and occupying the center of the picture at the same time.

The principle of the attachment herein described is the crossing of two beams of light at about right angles to one another at a point in the center of the field and at a distance of sharpest focus for the camera's lens system. A s the camera is brought toward the eye, two spots of light approach one another and, at the point of exact focus, they become one spot. If the camera is brought even closer to the eye the single spot again becomes two separate spots.

From Figure 1 it will be noted that the light sources are ordinary pen lights solidly mounted to metal posts attached to an alu­minum plate on the bottom of the camera. Each light may be raised, lowered, or ro­tated—then locked in position by means o f a bolt passing horizontally through the alu­minum plate. A portion of the bulb filament is focused as a beam by a small lens and two pinhole diaphragms in a tube attached in front of the bulb. These particular penlights

Fig. 1 (Nisbet). A focusing attachment for close-up photography.

have rotary switches posteriorly placed. A testing screen is attached to the alu­

minum base in front of the camera. Prior to taking each picture it may be noted, as soon as the penlights are turned on, whether or not the light spots appear as one on the center o f the screen. I f they do not, an adjustment may be made after which the testing screen is removed and the picture taken.

Although it has no relation to the focusing device, there is a cylinder (fig. 1) with a closed end covering the Strobe light tube. There is a hole in its wall through which the flash from the lower side of the tube may pass to strike a plane mirror mounted at an angle. The light is reflected directly over the camera lens to the eye. In this way maximum lighting is obtained, the camera diaphragm opening may be reduced, and greater depth of field obtained.

The apparent inconvenience o f verifying the focus prior to taking each picture or series of pictures is really unimportant in comparison to the accurate results obtained by photographing an eye at close range.

700 South McCullough.