Section II. EXPOSURE METER

1-8. General

General functioning of the exposure meter furnished with the KS-15(4) Still Picture Camera Set is described in TM 11-6720-244-12, paragraph 6-3. Following is supplemental information not contained in TM 11-6720-244-12.

a. Light Measuring Circuit (fig. a).

Light

Ш

1,1.3 5 volts

Meter

Figure a. Light Measuring Schematic.

A photo-resistor (CdS cell), battery and ammeter are in series. When the cell is dark it has an infinite resistance and no current flows. The resistance of the cell decreases in proportion to the intensity of the light incident to it. As light intensity increases, current flow increases and is measured by the meter.

b. Battery Test Circuit (fig. b).

I--1-1

Figure b. Battery Test Circuit.

Actuating the battery test switch disconnects the CdS cell and substitutes resistor (Rl). Resistor (R2) is placed in series with (Rl) and the battery. The meter is connected across (R2) and measures the voltage drop.

Section III. LENSES

1-9. General

General functioning of lenses furnished with the KS-15(4) Still Picture Camera Set is described in TM 11-6720-244-12, paragraph 6-2. All lenses in the set have parallel focusing mounts and couple with the cameras built-in rangefinder. Following is supplemental information not contained in TM 11-6720-244-12.

1 - 10. 35mm Lens Focusing Mount and Rangefinder Coupling

(Fig. 42)

a. Parallel Focusing. Focusing ring (20) is secured to the outer ring of the forward helix, which is part of the helical focusing assembly, by retaining ring (19). The inner portion of the helix has a milled slot which mates with a fixed guide in the differential focusing assembly. Rotation of the focusing ring moves the inner helix longitudinally. The fixed guide prevents it from rotating.

b. Rangefinder Coupling. The inner helix of the differential focusing assembly has a milled slot. This mates with a guide secured to the outer ring of the forward helix. Rotation of the focusing ring turns the inner helix, which actuates the camera rangefinder. It has a steeper pitch than the forward helix, and the same longitudinal displacement as a 50mm lens.

1-11. 50mm Lens Focusing Mount and Rangefinder Coupling

(Fig. 43, 44)

a. Parallel Focusing. Retaining ring (16), figure 43, secures the focusing ring assembly to the outer ring of the forward helix, which is part of helical focusing assembly (6), figure 44. The inner portion of the helix has a milled slot which mates with a fixed guide. Rotation of the focusing ring moves the inner helix longitudinally. The fixed guide prevents it from rotating-

b. Rangefinder Coupling. The 50mm lens has a two-step cam. The lower cam engages the rangefinder roller arm when focusing at distances between 3-feet, 4-inches and infinity. Its longitudinal movement is in direct relation to that of the lens elements. The higher cam actuates the rangefinder arm when focusing for closer distances. The height of the cam compensates for the increased forward movement of the lens in the close-up range. The longitudinal movement of the close-range cam is not in direct relation to that of the lens. The viewing unit, used in the close range, alters the rangefinder optical system.

1-12. 135mm Lens Focusing Mount and Rangefinder Coupling

(Fig. 47)

a. Parallel Focusing. The inner helix of helical focusing assembly (14) has a milled slot which mates with a fixed guide on differential cam assembly (8). Rotation of the focusing ring moves the inner helix longitudinally. The fixed guide prevents it from rotating.

6. Rangefinder Coupling. The differential cam has a milled slot. This mates with stop (11) which is secured to the outer helix of helical focusing assembly (14). Rotation of the focusing ring turns the differential cam. The inclined edge of the differential cam rides against a spring-loaded arm, which actuates the camera rangefinder. The longitudinal displacement of the arm differs from that of a 50mm lens. This is necessitated by the viewing unit which alters the optical system of the rangefinder.

c. Viewing Unit. The functioning of the 135mm viewing unit is described in TM 11-6720-244-12. paragraph 6-2d(3) (c).

Section IV. FLASH UNIT

1-13. Flash Unit

(Fig. 1-17).

The flash unit is powered by a B-C insert and connected to the cameras flash lamp socket by a connecting cord. It fits into the accessory clip on the camera, or may be hand-held for off-camera use. A tripod socket in the base of the flash unit permits tripod mounting. The reflector may be removed from the unit and folded for carrying in the universal case.

a. Mechanical Functioning. The reflector may be adjusted in height for centering with the flash bulb. Medium screw-base flash bulbs or, with an adapter, bayonet-base bulbs may be used. The bayonet-base adapter is equipped with a bulb ejector.

(1) Height adjustment of the reflector is secured by a spring in the reflector mounting bracket. The spring engages notches in the reflector handle.

(2) Medium screw-base bulbs are held in the lamp socket by spring clips which form part of the socket. The bayonet-base adapter fits into the medium-base socket in the same manner as a flash bulb. Bulbs are ejected by the adapters contact spring when the ejector button is depressed.

b. Electrical Functioning. The B-C (battery-capacitor) insert has a compartment for holding the 22-1/2 volt battery. The assembly fits into the flash unit housing. A selenium rectifier, in the base of the housing, prevents reverse current flow (premature firing) when using multiple units in parallel.

(1) B-C insert. The insert contains a 10,000-ohm resistor and 100 microfarad capacitor. Electrical connection is made by contact plates on each end of the insert.