US1926596A - Arrangement for printing photographs - Google Patents

Description

Sept. l2, l933.-

' ARRANGEMENT FOR PRINTING PHOTOGRAPHS Filed Jan. 6, 1930 lll A. NAUMANN 1,926,596

Patented Sept. 12,

mRANGEMEN'r Fon PRINTING PHOTOGRAPHS Arthur Naumann, Berlin, Germany, assignor to Voigtlander & Schn Aktiengesellschaft, Braunschweig, Germany, a joint stock comj pany of Germany Application January 6, 1930, Serial No. 418,825, and in Germany November 9, 1929 9 Claims. (Cl. 95-'73) This invention relates to a method and arrangement for printing photographs, which includes the printing from negatives on gaslightand silver-bromide paper, the printing of diapositive plates, the printing of positive cinematographic lms from negatives, the making of enlargements on silver-bromide paper, and the like. All these kinds of printing are referred to in the following description as the printing of 10 photographs or negatives.

The feature of thisinvention consists in determining and obtaining the proper intensity of electric light necessary for printing of any particular photograph or negative with a certain k constant lighting duration. The method .em-

ployed for setting the lamp to the proper intensity consists in determining the density of the negative to be copied on a density screen with the aid of a density measuring apparatus and in positively and automatically regulating, when adjusting the density screen, the effective value of a series resistance included in the electric circuit of the lamp, so that it iniiuences the lamp in proportion to the density measurement. In the use of this resistance-regulating apparatus the negative to be copied and a density screen are observed simultaneously through an eye-piece, and the density screen is adjusted until a degree of density is observed on the screen corresponding to that of the negative, that is until the degree of density observed on the screen is the same as the degree of density observed on the negative. By the adjustment of the density screen a sliding contact is shifted on a variable resistance. This variable resistance and the sliding contact are included in the electric circuit o! the copying lamp, and the intensity or the light alters with the shifting of the sliding contact on the variable resistance. The parts are so proportioned that the value of the resistance thus made eiective in the light circuit varies inversely with the density of the negative: the greater the density, the less the resistance, and consequently the greater the intensity oi the light. Instead of acting directly on the resistance by means of a sliding contact, the density `screenniay act upon an oscillatable adjusting lever which, on being oscillated, slides over contacts arranged side by side at suitable distances apart and connected to the windings of the resistance. This adjusting lever is also provided with a sliding contact, and this contact as also the resistance are connected to the circuit oi the lamp.

Two embodiments of the invention are illustrated hy way of example in the accompanying drawing in which Fig. l. shows in front elevation the resistanceregulating apparatus, and, diagrammatically, the lamp and the lamp circuit with which the resistance-regulating apparatus is associated.

Fig. 2 is a cross section of Fig. l.`

Fig. 3 shows a modied form of construction in iront elevation,

Like parts are indicated by the same reference letters in each of the diierent gures of the drawing.

A known apparatus is used for measuringr the density of the negative and consists of a tube a with an extension i and an eye-piece c in the centre portion and two tubular pieces d and e projecting at right angles, one from each end of the tube a. By means of an angular mirror ,t and two mirrors g and h, arranged one in each of the two tubular pieces, it is possible to look simultaneously through the two tubular pieces d and e. This piece of apparatus is conveniently mounted in a suitable stationary support ar. The negative 'i is placed in a seat formed in the support :1: tc receive it and in a position in front of sa the tubular piece d, and a movable gauge, for example, a density screen is is adjustably borne on a stationary support in :front of the tubular piece e. The density screen is is composed of transparent strips painted grey in absolutely uniformly 35, increasing degrees of density corresponding to the degrees of density occurring in negatives. Such density screens are known under the name of grey wedge. The holder. of the density screen is slidable in guides y in its stationary support; and in operation, when measuring the density of a negative, it is adjusted to such position that the degree of density visible in the eyepiece c corresponds with the density of the negative which, is also visiblein the eye-piece. 95

In so adjusting the density screen, the negative 'i and the screen k are simultaneously illuminated in equal degree by light from any suitable and convenient source. When considering the drawing, it .may be understood that negative and screen are, on the left (Fig. 2),` exposed to diffused sunlight, and that it is sunlight which, transmitted through them, is received through eye-piece c.

Associated with this density-measuring apparatus, means are provided for adjusting the intensity ofthe light emitted by the lamp of the printing apparatus. In the drawing this lamp o and its circuit are diagrammatically indicated. The printing apparatus is not otherwise shown;

it may be understood to be of usual character and to include, Within a box or other dark chamber, and in association with the lamp, suitable support for the negative and for the paper or other carrier with sensitized surface, upon which printing is to be effected.

The holder lof the density screen carries a sliding contact m on its under side, which contact slides on a series resistance n, and this contact as it slides brings into the electric circuit of the copying lamp o a greater or less quantity of resistance. A certain intensity of light with a certain duration is required, according to the density of the negative. The intensity of the lamp alters with the displacement of the sliding contact m on the resistance, and the resistance is such that the intensity of the lamp is always adapted to the degree of density of the negative-being adjusted in adjustment of the density screen. Thus, if the degree of density of the screen in the measuring apparatus is properly set to correspond with that of the negative, the negative can be exposed under the lamp with the proper intensity of light. The duration of the exposure (the intensity of the light being constant) is dependent upon the printing material used and upon the density of the negative, and the determining of the suitable length of exposure for the density of the negative is much more diiiicult and unpractical than k(the duration of the time of exposure being constant) is the determination of a suitable intensity of the printing light inthe manner described. A length of exposure suitable for the particular kind of printing paper to be used, and also the conditions existing in the apparatus above described, are predetermined and permanently preserved. A uniform length or exposure will always be maintained by means of a control clock p connected to the lamp circuit.

In use, the negative from which the print is to be made is first introduced into the resistanceadjusting apparatus and there becomes the determining factor by means of which the light circuit is brought to condition to afford, when the lamp is illuminated, light of proper intensity. When this has been done, the negative is removed from its position in the resistance-adjusting apparatus and introduced into the printing apparatus, in proper relation to the lamp and to the paper or other surface to be printed. The light circuit then is completed and light of an intensity so adjusted continues until, by the operation of the stop clock p, its circuit is broken again.

In the form of construction shown in Fig. 3 the holder Z of the density screen k acts on an adjusting switch q oscillatable around a pivot pin r and in oscillating causes its sliding contact. s to slide over contact terminals t, each of which is conductively connected with the series resistance n. The centre terminal t is connected with the centre of the resistance coil, and the terminals on each side are connected with the resistance coil at points on each side of the centre at properly spaced intervals. The adjustable holder Z of the density screen may act on the adjusting switch q in any suitable manner. According to the example illustrated a pin u, arranged on the holder l of the density screen and which may have a ball head atits end, engages in atubular extension o of the adjusting switch. In displacing the density screen when setting sameto the density of the negative, the pin u engages the regulating switch q on its neck part o and swings it accordingly, causing thereby thev sliding contact to slide over the contacts t and to be set to one of same. By this means the eiective length of the resistance n, through which the lamp current ilows, is so adjusted that the lamp has the intensity necessaryfor printing the negative, the density of which has been measured by the apparatus.

I claim:-

l. A system for printing photographs comprising in combination an apparatus with two openings for measuring the density of the negative, a density gauge, the negative to be printed and the said gauge being placed each in front'of one of said openings ofv the apparatus, an adjustable holder for the gauge, a sliding contact on said holder, an electric lamp, and a series resistance, said sliding contact and said series resistance being connected to the electric circuit of said lamp, and said sliding contact adapted to slide on said series resistance.

2. A system for printing photographs, comprising in combination an apparatus with two openings for measuring the density of the negative, a density gauge, the negative and said gauge being placed each in front of one of said openings of the measuring apparatus, an adjustable holder for said gauge, a sliding switch, said holder acting on said sliding switch, an electric lamp, a lamp-energizing circuit, a resistance coil arranged in said circuit and in series with said lamp, said sliding switch being also included in said circuit and being movable to successive positions of contact at intervals along the windings of said resistance coil.

3. A system for printing photographs, comprising in combination an adjustable apparatus for measuring the density of lthe negative, a source of light, means connected up in the circuit of said source of light and movable in response to adjustment of said density-measuring apparatus for adjusting the intensity of said source of light to the density of such negative, and a switch watch also connected up in the circuit of said source of light.

4. A system for regulating the active light intensity for photographic printing, comprising an instrument for visually ascertaining the density of the negative to be printed, a source of light, and means operatively connected with said instrument for regulating the active light intensity of said source of light.

5. A system for regulating the active light intensity for photographic printing, comprising an instrument for Visually ascertaining the density of the negative to be printed, a source of light, and means operatively connected with said instrument for regulating lthe intensity of the light emitted from the said source.

6. A system for regulating the active light intensity for photographic printing, comprising an instrument for visually ascertaining the density of the negative to be printed, an electric lamp and its circuit, and means operatively connected with said instrument for regulating the current supplied to said lamp.

'7. A system for regulating the active light intensity for photographic printing, comprising an instrument for visually ascertaining the density of the negative to be printed, an electric lamp and its circuit, and means directly connected with said instrument for regulating the current supplied to said lamp.

8. A system for regulating the active light ininstrument for visually ascertaining the density llil of the negative to be printed, a source of light, means operatively connected with said instrument for regulating the active light intensity of said source of light, and time-controlled mechanism for throwing said 'source of light out of operation.

ARTHUR NAUMANN.

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