Abstract: A light measuring apparatus for measuring the light transmitted through filters to a light sensor is equipped with a filter wheel having non light transmissive segments alternating with the light transmissive filters, which filter wheel is manually rotatable by a lever. By repositioning the lever through a certain angle, its motion is translated via a spring and various gears and additional transmission elements to rotate the filter wheel and periodically shield the light sensor. The shielding of the light sensor for short periods permits a determination of an error signal in the light measuring apparatus. To obtain a shielding time period above a required minimum independent of the speed with which the lever is moved, the motion of the filter wheel is automatically delayed by mechanical means.

Abstract: In a circuit for the control of exposure time with photographic enlarging equipment with variable enlargement ratio, and with a device for determining light quantity, a light sensitive electric transducer is provided a fixed distance to the negative plane of the enlarging equipment. Means for generating a signal representing the enlargement ratio, in the form of a potentiometer, modifies the signal derived from the device for determining light quantity to thereby produce a signal representative of the proper change of exposure time for a selected enlargement ratio. The circuit incorporates function generators to modify the signal from the light sensitive electric transducers to allow for the correction of the failure of the reciprocity law.

Abstract: An illuminating system for use in a photographic enlarging apparatus having first and second light control channels is disclosed. The light control channels receive and transmit light from a light source; the light exit end of the first light control channel has a diagonal that is less than the longest side of the cross-section of the light entrance end of the second light control channel. A picture stage for receiving and supporting a negative to be projected is secured to the light exit end of the second light control channel. The second light control channel and the picture stage are mounted for unitary rotational movement about an axis normal to the plane of the negative.

Abstract: An illuminating system is provided with a source of light for generating a beam of light having a ratio of energy distribution at three wave length ranges that differ from the spectral sensitivity of photographic copying material at those three wave length ranges. Color filters are inserted into the beam of light to a depth for compensating for the disparity between the energy distribution and spectral sensitivity. One of the filters is of a filter color that influences the wave length ranges having the highest energy levels in excess of a desired energy; a second filter of a second filter color influences only the wave length range with the largest energy excess over the desired energy level.

Abstract: An apparatus for determining the color composition of the printing light of a photographic enlarger samples and measures the light within the intermediate diaphragm chamber of the objective lens. The light is sampled by inserting color-sensitized photoelectric transducers within the intermediate diaphragm chamber or inserting a light conducting means within the chamber between exposures for sampling and conducting the light outside of the chamber to external photoelectric transducer means, which determines the color content in any operative manner. The light conductor may be mounted on a slide together with an adjustable diaphragm for alternating inserting in the path of the printing light or the light conductor and a number of apertures of different cross-sections may be mounted on a rotary disk for optional insertion along the optical axis. The light conducting means includes a diffusing element within a light conducting and reflecting chamber.

Abstract: The color composition of printing light in a photographic enlarger is sampled by rotating a sampling duct between the original image holder and the objective lens. The duct has a thin elongated rectangular shape with a light diffusing aperture disposable in the printing light and with mirrored inside walls, which transmit a representative sample of the printing light to the outlet aperture, which is disposed in front of light measuring receivers. The receivers generate a signal which is processed to govern the insertion of filters in the light-mixing head of the enlarger to provide the desired color composition in the printing light. A convenient push control and actuating switch arrangement is provided to simplify insertion of the duct in the printing light before and its removal during the printing exposure.

Abstract: An illuminating device for a color printing apparatus having color filters insertable at varying amounts into the printing light beam has a light-conducting shaft and a variable aperture diaphragm both of which have substantially rectangular cross sections whereby the color content of the printing light beam is maintained substantially uniform. The light-conducting shaft has the form of a frustum of a square pyramid and the variable aperture of the diaphragm has a rectangular form. The light source has an ellipsoidal reflector, and the light beam emerging from the illuminating device is channeled through a light mixer.

Abstract: A light mixing compartment for a projector, such as incorporated in a photographic copier or enlarger, has four convexly curved side panels disposed between the entrance and exit, which are covered by light diffusing plates. The cross sections of the compartment parallel to its diffusing plates are cylindrical or rectangular with the sides having different angles of inclination adjacent the entrance from those at the exit. The ultimate slope of the sides adjacent the exit preferably is a right angle, and the overall shape of the convexly curved sides is adjusted to control the marginal brightness of the light format emitted from the compartment. The four convexly curved sides are held together by appropriately shaped bands riveted to the sides for securing them together.

Abstract: A closed container for wet processing photographic strip or sheet materials such as film or printing paper has a cover piece which rests upon several of the conveying rollers. The cover piece has indentations in its lower surface which correspond to the outer surfaces of the rollers to smoothly engage them with intermediate portions of the cover piece being submerged in the processing liquid. This minimizes the contact of the air in the container with the wet surfaces of the rollers partially submerged in the liquid and inbetween them, which thus minimizes oxidation of the processing baths.

Abstract: In a photometric circuit a reference current is supplied into the input of the logarithmic amplifier at the same time the signal compensating the error originating in the photocell is supplied to the circuit. The reference current corresponds to the current which would occur in the photocell for the lowest measurable intensity of illumination. A sum-and-difference amplifier has one of its inputs supplied by the output of the logarithmic amplifier and its second input is supplied by a reference voltage. The control loop contains a storage capacitor connected after the sum-and-difference amplifier and an impedance converter connected after the storage capacitor. The compensating and reference currents are controlled by switches synchronized with a light chopper mounted in front of the photocell.

Abstract: The color mixing compartment of illuminating equipment for a photographic enlarger includes two parts. The part adjacent the light-admitting surface is a truncated pyramid. The part adjacent the light-emerging surface is substantially a parallelepiped having side faces disposed substantially perpendicularly to the light-emerging surface. A diffusing plate having a substantially uniform thickness is arranged at the light-admitting and light-emerging surfaces of the mixing compartment.

Abstract: A blocking filter is used, in conjunction with the substractive filter method of copying photographic color images, to remove or substantially remove by greatly weakening wave lengths from the copying light in the range in which the filter characteristics of the blue and green color filters or the spectral sensitivity curves of photographic copying paper overlap each other, or more particularly in a 30 nm belt about a central wave length of approximately 500 nm.

Abstract: A mechanism, for adjusting the position of an illuminating lamp longitudinally and angularly in planes perpendicular to the optical axis of the condenser, has a lead screw and guide rod mounted substantially parallel to each other on the housing. The lamp socket holder is longitudinally traversed by the lead screw and the guide rod is eccentrically adjusted to impart a tilting movement to the holder. Control knobs for the lead screw and tilting mechanism are disposed adjacent each other on the outside of the housing. The lamp socket may also be axially and rotatably adjusted in the holder.

Abstract: The filter insertion settings of a colored light projector are determined by projecting the colored light through different light color windows of a test probe onto a light measuring device to provide a predetermined signal. Diaphragms on the color windows are adjusted to provide a predetermined balanced format for a predetermined balanced light condition. The filters on the projector are adjusted for a given light, such as through a color negative to be printed, to cause the aforementioned predetermined signal to be generated by the light measuring device. Different settings on different probes may be provided for different series of predetermined desirable color formats or combinations, such as for different types of color negatives -- for example, for verdant scenes or sea scapes. The optical diaphragms may be conveniently provided by adjustable screws running into the windows.

Abstract: A color filter-determining apparatus, which indicates the color component to be balanced, has two measuring circuits, each of which contains a pair of photoelectric transducers. One of the photoelectric transducers in each measuring circuit is sensitive to the same primary color and the other transducers are sensitive to different primary colors. The measuring circuits comprise resistance measuring bridges, which are complemented by resistors and diagonally supplied by separate power sources and also diagonally connected to inputs of operational amplifiers, such as sum-and-difference amplifiers.

Abstract: Three measuring channels in a photographic color printing and enlarging apparatus are utilized for determining the filter values of the primary colors. The exposure time is determined by adjusting and reading the amplification factor of an amplifier which amplifies the signal of a light-voltage transducer containing a photoelectric element, which obtains its input from a measurement of each of the three primary color components in the printing light. The light-sensitive element of the photoelectric element has a characteristic curve which is linearly related to the intensity of illumination and it is preferably a photodiode. The light impinging on the photodiode is modulated by an electromechanical light-chopping device and the measuring signal is controlled by a zero-regulator. The light-sensitive element, the zero-regulated device, the light-chopping device and filter controlling device are miniaturized and fitted into a light-measuring probe.

Abstract: This invention relates to a light-measuring apparatus wherein a photoelectric element is arranged in a leg of a measuring bridge, the output voltage of said element controlling the brightness of two signal lamps.