GB2260462A - Colour reversal viewing of negative film - Google Patents

Abstract

Colour reversal viewing of a negative film on a viewing screen is achieved by positioning a negative picture 7 in the focal range of an optical assembly 8 of a camera 2 for converting light from the picture into a video signal, ensuring that the negative is adequately illuminated and in focus using the camera apparatus to generate a video signal representing the picture in configuration and colour, processing the video signal electronically in a colour reversal circuit 3 to effect a colour reversal of the picture and transmitting the colour reversed video signal for video recording and/or display on a screen 4. <IMAGE>

Description

METHOD AND APPARATUS FOR COLOUR REVERSAL VIEWING OF NEGATIVE FILM The invention relates to a method and apparatus for colourreversal viewing of negative film and pictures, such as 35 mm film stock, colour reversal negatives or, black and white negative transparency film stock. Such film stock is semitransparent to allow the transmission of light. Principally the viewing is done through a television display, however an intermediary step of video recording may be involved if required. The method and apparatus conveniently involves the use of a video cam-corder, although the optical system and circuity used in the cam-corder may be incorporated in apparatus specifically designed to operate according to the present invention. Alternatively, the reversal unit of the present invention could be built into the housing of a camcorder.

It is known from US Patent No 4,676,628 to view a colour negative on a video display, such as a monitor television receiver by way of a video camera, as part of the colour analysing and colour balance correcting process or photographic printing.

It is also known from Patent No WO 88/08235 to view, on a television screen, a colour print which is front illuminated so that reflected light is converted into a video signal by a video camera for video recording and/or display.

The primary colours for reflected light are red, yellow and blue whereas the fundamental transmission colours are cyan, magenta and yellow which are the complementary colours used in colour negative film stock to print in the primary colours on colour photographic paper according to known so called colour reversal print processing.

The present invention seeks to provide a colour reversal of the colours on negative film. For the avoidance of doubt and for the purposes of this specification the term "colour" is used to include "black and white", and "film" embraces photographic plates and other media carrying pictures or images. Additionally, the term "viewing screen" includes the screen of a television set (TV) or video monitor, a planar video display, or other screens capable of displaying pictures from an electrical video signal input.

According to the present invention there is provided a method of colour reversal viewing of a negative film on a viewing screen comprising the steps of: positioning a negative picture in the focal range of an optical assembly of camera apparatus for converting light from the picture into a video signal; ensuring that the negative is adequately illuminated and in focus; using the camera apparatus to generate a video signal representing the picture in configuration and colour; processing the video signal electronically to effect a colour reversal of the picture; and transmitting the colour reversed video signal for video recording and/or display on the screen.

The transmission of the colour reversed signal may be directly to a television set or by way of storage on a video signal storage medium such as a video tape used in a VCR.

Preferably the camera apparatus is a cam-corder having a macro-focusing optical assembly. The negative picture may be mounted in front of the cam-corder lens in a frame holder at a preset distance from the lens so as to be in focus without the need for further focusing of the optical assembly. The colour reversed video signal may be modulated on a carrier at a UHF frequency within the range of a television set, or the signal may be at a baseband frequency for inputting to the television set via the SCART socket.

According to a second aspect of the invention there is provided apparatus for colour reversal viewing of a negative film comprising: an optical system for focusing on the negative film; a video signal generating means for generating an electronic signal representing the configuration and the colours of the image on the negative film; a colour reversal circuit for processing the video signal so that it maintains the configuration and incorporates complementary colour information; and an output circuit for outputting a video signal for recording and/or direct viewing in normal colours on a viewing screen.

The invention may utilise the optical system and video signal generating means of a cam-corder so that the output of a standard cam-corder is fed to the colour reversal circuit which may be housed within the cam-corder and switched into circuit when required so that the output circuit of the cam-corder can be used as the output circuit of the invention.

The invention will now be described by way of example with reference to the accompanying diagrammatic drawings in which:- Figure 1 shows schematically the elements of the invention; Figure 2 shows a negative viewer enclosure; Figure 3 shows a circuit for converting a camera input signal into a video signal with the colour components of the image; Figure 4 shows a circuit for processing the video signal; Figure 5 shows a colour component encoder and output circuit; Figure 6 shows schematically the signal processing circuits; Figure 7 shows the detailed circuit for d.c.

equalisation prior to processing; and Figure 8 illustrates the signal waveforms referred to in the operation of the invention.

Figure 1 shows a negative film holder 1 mounted on a camcorder 2 the video signal output of which is fed via a colour reversal processing circuit 3 to a television set 4 and/or to a video recorder 5.

In operation light from a light source 6, which may be ambient light, is transmitted through a film negative 7 into the lens system and optical assembly 8 of the camera 2. The optical system of the camera is focused on the negative 7 using the macro-focusing facility of the cam-corder 2. The video signal output from the cam-corder 2 represents the configuration and transmitted colours from the negative 7.

This video output signal is processed by the circuit 3 which encodes the video signal with complimentary colour information so that the signal fed to the viewing screen 9 of the television set 4 enables viewing of the image on the negative 7 in its normal colours.

Having therefore described the basic steps of the invention, specific apparatus and circuits will now be described with reference to Figures 2 to 5 and Figure 7, to more fully described as a preferred embodiment of the invention.

Referring now to Figure 2, which shows a negative viewer enclosure 10 designed to be coupled with the lens system of a cam-corder. The lens system of the cam-corder is cradled in a cradle 11 immediately adjacent a negative film holder formed by a guide-way 12, a lens spacer 13 and a light source and diffuser 14. The enclosure 10 is arranged to house batteries not shown which are accessible for replacement purposes by removal of the lid 15.

Alternatively, the light source and the electrical circuit within the enclosure may be connected to an external power source by way of a mains input socket 16.

The electrical circuitry within the enclosure 10 is controlled by a power on/off switch 17, a brightness control 18, a contrast control 19, a hue/tint green control 20 and a blue control 21. The video signal is fed to the colour reversal processing circuit by way of an input socket 22 and the processed video output signal is derived from an output socket 23.

In operation a film strip or a negative slide holder containing slides is located in the guideway 12 and illuminated from the diffused light source 14. The lens spacer 13 ensures that the lens system of the cam-corder (as shown in Figure 1) is held in the cradle 11 and spaced sufficiently from the negative film to ensure that the macro focusing of the lens system can be adjusted to produce a sharp image in the viewer of the cam-corder. The output signal from the cam-corder is fed to the video input 22 for colour reversal processing as will be described with reference to Figures 3 to 8. The processed video output signal is fed from the socket 23 to a VCR or television set for viewing in normal colour.A Normal/Negative switch 24 is also incorporated in the enclosure 10 which facilitates negative films and colour reversal prints to be viewed in succession by operating the switch 24.

Referring now to Figure 3 the input socket 22 is connected to a contrast control potentiometer 25 (operated by the slider of contrast control 19 of Figure 1) of a luminance filter 26. The output from the potentiometer 25 is connected to input 27 of an integrated circuit 28 (as sold by Sony under reference V7021). The input signal from socket 22 is also fed via a chrominance filter 29 to input 30 of the integrated circuit 28.

The red, green and blue signals are derived from the integrated circuit 28 from output terminals 31, 32 and 33 respectively. The sub-carrier signal is derived from terminal 34, the sync signal derived from terminal 35 and the B-flag signal from terminal 36. The controls 18 to 21 as shown on Figure 2 operate the sliders of potentiometers to control the brightness, contrast and colour (green and blue) respectively. The output signals on terminals 31 to 34 of the integrated circuit 28 provide input signals to the circuits shown in Figure 4 and 5 which will be described in detail later.

Referring now also to Figure 4, the B-flag signal from terminal 36 of integrated circuit 28 provides the input to the blanking signal circuit 37 (containing a Philips integrated circuit sold under the reference PC74HC123). The width of the blanking signal is adjusted by potentiometer 38. The B-flag signal shown as the input to circuit 37 is modified to form the output signal at output 39 (as illustrated in Figure 8).

The sync signal from terminal 31 of Figure 3 is inverted by circuit 40 of Figure 4 to provide a clamp signal at output 41 (as shown in Figure 8b). The blanking and clamping signals from outputs 39 and 41 respectively are fed to each of the colour processing circuits 42, 43 and 44. Circuit 42 processes the red signal from output 31; circuit 43 processes the green signal from output 32; and, circuit 44 processes the blue signal from output 33. Potentiometer 45 (adjusted by means of the slider of control 18 shown in Figure 1) controls the intensity of the red, green and blue output signals appearing at terminals 46, 47 and 48 respectively. The sliders of green and blue controls 20 and 21 respectively as shown on Figure 2 operate the potentiometers 49 and 50 respectively.

Referring now also to Figure 5 the red/green/blue encoder comprises an integrated circuit 51 (as sold under reference CXA1145). The red, green and blue output signals from terminals 46, 47 and 48 respectively of Figure 4 are coupled via capacitors to pins 52, 53 and 54 respectively of the integrated circuit 51. The sub-carrier signal from output 34 of integrated circuit 28 (shown in Figure 3) is coupled via a capacitor to pin 55 of integrated circuit 51. The sync signal from terminal 35 (shown in Figure 3) is directly coupled to input pin 56 of the integrated circuit 51 (as shown in Figure 5). The complementary colour signal after colour reversal processing, as just described, is derived from output pin 57 which is coupled by way of a capacitor and resistor to input terminal 58 of a switch 24 (as shown on the enclosure 10 of Figure 1).The other input terminal 59 to the switch 24 is connected to terminal 22 of Figure 3.

The switch 24 may be operated to connect the video input signal from terminal 22 or the colour reversal signal from the encoder 51 to the video output terminal 23 (as shown on Figure 2). The terminal 23 may be coupled to the video input of a television set or recorder as previously described.

Referring now to Figures 6, 7 and 8, Figure 6 shows schematically the signal processing circuits. The video input signal at terminal 22 is applied to a PAL/NTSC decoder 60 which produces red/green/blue output signals together with a sync signal which are applied to a video signal processor 61. The red/green/blue and sync signals from the processor 61 are coupled into a PAL/NTSC decoder 62 from which the video output signal is derived via the switch 24 from terminal 23.

The contrast is controlled in decoder 60 and brightness and hue or tint is controlled in the processor 61 the specific circuits for which have previously been described.

Referring now also to Figure 7, in operation, the PAL/NTSC decoder 60 provides red/green/blue video signals with the sync signal stripped off. These signals must be d.c.

equalised prior to processing. As shown in Figure 7 a capacitor 63 couples the video signal to the base of transistor 64 which is clamped from the sync signal applied to transistor 65. The brightness is controlled by the potentiometer 45 connected to the emitter of the transistor 65. The d.c. restored signal is buffered by the emitter follower transistor 64 and a positive-going pedestal signal is inserted via a diode 66 connected by way of a potentiometer to the pedestal signal input. A monostable circuit is used to generate the pedestal signal. The height of the pedestal in relation to the video signal is critical.

By varying the height of the individual colour signals the brightness of the colour signal is varied. It should be noted that the signal is fixed for the red colour signal and only the green and blue signals are adjusted by controls 20 and 21 operating on potentiometers 49 and 50 (as shown on Figure 4).

The combined output signal from transistor 64 and diode 66 is coupled to the encoder circuit via transistor 67 which inverts the signal applied to the encoder 62. It will be seen that the pedestal in the inverted signal now acts as the output black level reference. It is important that the overall gain and brightness and tint levels do not result in negative-going video signals falling below the black level.

This is ensured by controlling the range of the potentiometers assisted by the automatic iris operation available in most video cameras and cam-corders to limit the incident light.

Figure 8 illustrates the waveform of signals referred to with reference to Figures 1 to 7 in which : Figure 8a represents the video input signal derived from terminals 31, 32 and 33 of Figure 3; Figure 8b illustrates the clamp signal from terminal 41 of Figure 4; Figure Sc illustrates the B-flag signal from terminal 36 of Figure 3; Figure 8d illustrates the pedestal signal from terminal 39 of Figure 4; Figure 8e represents the composite signal with variable brightness control as applied to the base of transistor 67 of Figure 7, and Figure 8f illustrates the inverted video output signal with variable tint above the black level, which signal is applied to the encoder 62 of Figure 6.

It will be appreciated that the invention may be incorporated into a cam-corder so that by switching between the normal mode and the colour reversal mode it may be used to view and/or record both negative and positive films or pictures. The mounting for the film may need to be rotatable through 90 to accommodate different orientations and aspect ratios of the film.

Alternatively instead of incorporating the system in a camcorder, and particularly for existing cam-corders it may be preferable to provide an individual unit which provides the necessary signal inversion whilst permitting the camcorder to provide the auto-white balance.

As negative film is often provided with sprocket holes the film guideway may be provided with a sprocketed wheel so that the film may be indexed from one view to the next.

Claims (12)

Claims

1. A method of colour reversal viewing of a negative film on a viewing screen comprising the steps of: positioning a negative picture in the focal range of an optical assembly of camera apparatus for converting light from the picture into a video signal; ensuring that the negative is adequately illuminated and in focus; using the camera apparatus to generate a video signal representing the picture in configuration and colour; processing the video signal electronically to effect a colour reversal of the picture; and transmitting the colour reversed video signal for video recording and/or display on the screen.

2. A method of colour reversal viewing as claimed in claim 1, wherein the transmission of the colour reversed signal is directly to a television set.

3. A method of colour reversal viewing as claimed in Claim 1, wherein the colour reversed signal is transmitted to and stored on a video signal storage medium such as a video tape used in a VCR prior to being onwardly transmitted to a display screen.

4. A method of colour reversal viewing as claimed in any preceding claim, wherein the camera apparatus is a camcorder having a macro-focusing optical assembly.

5. A method of colour reversal viewing as claimed in any preceding claim, wherein the negative picture is mounted in front of the cam-corder lens in a frame holder at a preset distance from the lens.

6. A method of colour reversal viewing as claimed in any preceding claim, wherein the colour reversed video signal is modulated on a carrier at a UHF frequency within the range of a television set.

7. A method of colour reversal viewing as claimed in any one of Claims 1 to 6, wherein the signal is at a baseband frequency for inputting to the television set via the SCART socket.

8. Apparatus for colour reversal viewing of a negative film, the apparatus comprising an optical system for focusing on the negative film, a video signal generating means for generating an electronic signal representing the configuration and the colours of the image on the negative film, a colour reversal circuit for processing the video signal so that it maintains the configuration and incorporates complementary colour information, and an output circuit for outputting a video signal for recording and/or direct viewing in normal colours on a viewing screen.

9. Apparatus for colour reversal viewing as claimed in Claim 8, wherein the optical system and video signal generating means are provided by the appropriate components of a cam-corder, the output of which is fed to the colour reversal circuit

10. Apparatus for colour reversal viewing as claimed in Claim 9, wherein the optical system and video signal generating means are housed within the cam-corder and switched into circuit when required.

11. Apparatus for colour reversal viewing substantially as herein described with reference to the accompanying drawings.

12. A method of colour reversal viewing substantially as herein described with, reference to the accompanying drawings.