FR2679343A1 - METHOD FOR PHOTOGRAPHIC REPRODUCTION OF SURFACES ADJUSTED BY MOVING LIGHT. - Google Patents

Abstract

A method for the photographic reproduction of certain defined surfaces based on the guided movement of a lighting device near the surface to be reproduced by means of a controlled dolly having two degrees of mobility (patent application no. 91-08897, Paris, 15 July 1991). The filming apparatus, which is located further away from said surface than is the lighting system, is arranged in such a way that the film is exposed during the time the light is in motion. This method is mainly designed for photographing works of art, drawings, sets, tapestries or maps which are mounted on plane, conical or cylindrical surfaces, regardless of their slope and length, which are several metres wide and located at any height above the ground. Each of these parameters is taken into account when settings are made prior to shooting.

Description

 The invention relates to a method of photographic reproduction of certain regulated surfaces (planes, cylinders or cones) based on the controlled movement of a lighting device near the surface to be reproduced according to a double controlled tracking shot (patent application No. 91 -08B7R Paris, July 15, 1991). The camera, further away from the surface to be reproduced than the lighting system, is prepared so that the film is exposed for the duration of the movement of the light. In the most common configurations, the dual tracking device is perfectly removable and transportable, which makes it conform to the uses of professional photographers.

 Two lighting techniques are currently used in the photographic reproduction of works of art or architecture.

 The first consists in illuminating the entire surface to be reproduced by two (or more) lamp systems located on either side of the surface. These systems diffuse a light chosen by the operator which reaches the surface with an angle of incidence of approximately 45 o. The adjustment consists in balancing these two side lights. The disadvantages of this process are as follows: - balancing the light sources is difficult.

- the use of several light sources induces untimely differences in color temperature, and for example unilateral or local yellowing effects in the photograph.

- double lighting, by erasing the shadow effects, distorts the visual impression, which prevents the restitution of the fine texture of the surface to be reproduced or of certain pictorial techniques (painting with a knife for example).

- areas of reflections and areas of shadows disturb the effects desired by the artist.

- This last drawback is particularly unacceptable in the case of large works, or decorations.

 The second technique is based on the ancient principle of overprinting (1908).

It is used, for example, for taking pictures in architecture. Its principle consists in exposing the film to precise and intermittent lighting, the operator composing the reproduction through the play of their succession. Applied without further elaboration to art photography which calls for uniform lighting of the reproduced object, this technique poses insoluble problems of covering the surface to be reproduced.

 A method addresses some of these difficulties in the case of flat surfaces of fixed and limited dimensions ("Scanning light system" patent; United States, n0462942, February 1, 1983; Europe, n00124195, October 19, 1988). A light source and a reflector sweep by snaking the surface to be reproduced, they circulate on a tubular portico in the shape of rectangular parallelepiped. The source is orientable in the plane perpendicular to the direction of movement and to the surface, at an angle varying from 400 to 800 with the vertical. Several disadvantages then arise: - the need to mount, for each class of works of art characterized by their dimensions, a tubular apparatus for ad hoc guidance.

- the heaviness and the difficulty of implementing the device in the case of the reproduction of large areas.

- the limits of the process as regards the nature of the reproducible surfaces: these are necessarily vertical planes close to the SoL Non-planar configurations would induce untimely effects of luminosity. Wall decorations distant from observers, ceilings, are only accessible at the cost of scaffolding assemblies.

Tables hung not vertically (however the most frequent case in museums or galleries) call for manipulations of removal or wedging of the tubular device which make it unstable, in the criminal works to reproduce.

- the weakness of the thermal protection granted to the photographed works: that offered by an infrared filter does not always satisfy the owners of the works.

- the arbitrary limitation of the orientation of the lighting to a deflection at a degree of freedom from 40 to 800, certain textures or certain pictorial procedures being able to justify a two-dimensional adjustment (from O to 1800 around the vertical of the lit place , from Oc to 1800 with respect to this vertical).

- in general, the excessive limitation, in the description of the process and its method, of choices which, in fact, involve the know-how of the photographer in front of each work to be reproduced: reflector, light source, film, speed and path lighting.

 The present invention solves these various difficulties by distinguishing two orders of problems, those of mechanical displacement of the lighting in the least demanding conditions possible for the photographer (use of a light displacement process known as "double tracking traveling"). , those photographic of the restitution of the work to reproduce. The process thus gives the photographer complete freedom to define the single light source used, to adjust the orientation of this source relative to the generic element of illuminated surface, the choice of film, and finally to adjust the opening and exposure on the camera. These four settings depend in fact on the nature of the object reproduced, they implement the expertise of the skilled person.

 Double controlled tracking makes possible the effective use of a single mobile lighting thanks to which the exposure of the film takes place in overprinting. The disadvantages of the techniques mentioned are thus avoided. The dual tracking settings registers ensure the suitability of the new photographic process for a wide range of objects to be reproduced and allows all of the resources known to specialized photographers to be deployed without exclusion.

 This double enslaved traveling, for its principle, consists in moving on a traditional traveling a carriage surmounted by a mast adjustable in height at the top of which an articulation accommodates, in balance, a second device whose azimuth is adjustable ("orientable traveling" , patent application No. 91-08870, Pans, July 15, 1991). This second device consists of two parallel head-to-tail rails, separated by spacers. On one of them circulates a support provided with a double ball joint on which is fixed the lighting for the present invention. On the other symmetrically circulates a counterweight. The center of gravity of the traveling tracking is always located at the top of the mast, which ensures the stability of the assembly and contributes to the regularity of the movement of the carriage. The two movements, that of the light support on its rail and that of the carriage on the ground, are controlled. This set, in common configurations (work located up to several meters high, several meters wide, any length), is removable and portable.

Its mounting and adjustment is in line with the working habits of professional photographers.

All the adjustments imposed by this process correspond to the following parameters: 1 - Geometric configuration of the surface to be reproduced 1.1 - Path governing the generation of the surface. It's the focus,
on the ground, of the tracking path on which the carriage will move 1.2 - Average height of the surface. Height adjustment of the top of the mast 1.3 - Azimuth of the line generating the set surface. Position adjustment
orientable tracking at the top of the mast 2 - Light source (See also parameter 3.4).

2.1 - Choice of the light source. Left to the discretion of the photographer.

2.2 - Choice of the possible light reflection device. Left to the discretion of
photographer.

2.3 - Choice of filters. Left to the discretion of the photographer.

2.4 - Adaptation of the cooling system Expulsion by air ventilation
heat produced by the lighting and / or infrared filter.

3 - Orientation and displacement of the light source on its support 3.1 - Orientation with two degrees of freedom of the source on its support Left at
appreciation of the photographer.

3.2 - Amplitude of circulation of the support in its linear displacement. Terminals
electromechanical (relay) or photoelectric, or programming.

3.3 - Speed of circulation of the support during this linear displacement. Parameter of
the intensity of the adjustment adjusted by dimmer or by programming.

3.4- Control of the linear displacement of the support to the path of the double
tracking shot. Electromechanical process (relay + dimmers + timers), photo
electrical (cells), or electronic (programming), or any combination of
these This servo defines the scanning of the light source on the
surface to be reproduced. I1 can take all the paths characterized by the
displacement of a point on the line of generation of a regulated surface.

Several passages are possible, each of them covering all or part
of the surface, the characteristics of the light source (intensity, filtering)
can be changed between two passes.

4-taken
4.1 - Positioning of the camera. In art photography, the camera
is generally more distant from the work than lighting, its position depending on the
field to enter. Left to the discretion of the photographer.

4.2 - Choice of film. Left to the discretion of the photographer.

4.3 - Adjusting the exposure. The film is exposed when moving the
light. The rest is left to the discretion of the photographer.

4.4 - Elimination of unwanted light. Placing covers on the elements
of the device that require it Left to the appreciation of the photographer.

This process is mainly intended for the photography of works of art,
decorations, tapestries, maps or plans that follow a flat, conical surface
or cylindrical of any inclination and length, of a width of several
meters and located at any height from the ground. As such, it is particularly suitable for the reproduction of paintings (vertical planes), possibly without the need to remove the original (inclined planes); large frescoes, walls or tapestries (vertical planes); decorations
non-planar murals (vertical cylinders); decorated ceilings (horizontal or
inclined, cones).

Claims (3)

 1) Photographic reproduction process of certain regulated surfaces (planes, cylinders or cones) according to the technique of overprinting caractéAsé in that a light is moved close to the surface to be reproduced by means of a double traveling tracking device; in that this lighting consists of a light source, filters and a cooling system; in that the orientation of this lighting is fixed relative to the generic element of the illuminated surface by playing on the one hand on the angle of the light relative to the vertical of this element and on the other hand on its rotation around this vertical; in that the camera is placed farther from the surface to be reproduced than the lighting, and in that the film is exposed for the duration of the movement of the lighting.  2) Method according to claim 1 characterized in that one proceeds to several scans of the different parts of the object to be reproduced, the focus of the lighting and that of the camera can be changed between two scans.  3) Method according to any one of the preceding claims, characterized in that it suppresses, by means of covers, untimely reflections which could affect the exposure of the film.