JPS6131306Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a camera filter that cuts out red areas.

Conventionally, camera filters for cutting out red areas include a red transmitting filter for contrast and a cyan filter for color compensating. The former is made of colored glass, dyed plastic, or dyed gelatin, and is mainly used to create a contrast effect in black and white film.
As shown in the spectral transmission curve in the figure, it is a filter that absorbs wavelengths shorter than red light and transmits wavelengths longer than red light. The latter uses dyed gelatin to transmit a wavelength range shorter than red light, as shown in Figure 4, mainly to change the color balance of images taken with color film or to compensate for the lack of spectral characteristics of the light source. This is a filter that changes the degree of transmission of red light. However, the above filter has the disadvantage that the following effects cannot be obtained.

In other words, some of the organic dyes currently used in a wide variety of textiles strongly reflect red or infrared light at the longest wavelength, which is barely perceptible to the human eye. be.
The spectral composition of the color stimulus seen by the human eye in color terms is shown in Figure 5 using CIE (Commission Internationale de l'Eclairage) spectral tristimulus values. It has a spectral curve as shown in the figure. Therefore, the color film is sensitive to the above-mentioned red light or strong reflected light in the infrared region. This effect is particularly noticeable in green or dark green fabrics (for example, dyed fabrics with a spectral reflectance curve as shown in FIG. 7), which has the disadvantage that gray or warm colors are reproduced. To prevent this phenomenon, methods of retouching using retouching or masking techniques during printing are currently employed, but these methods are difficult, time consuming, and expensive. As is clear from the above figure, when using color film to photograph a fabric that strongly reflects red light, which the human eye can only slightly perceive, the color film will perceive it more than the human eye, and the human eye will be unable to see it. Fabrics that appear green to the eye end up appearing gray or warm-toned in the photo.

This idea was made in order to eliminate the above-mentioned drawbacks of the conventional methods, and involves forming a vapor-deposited film on optical glass, plate glass, or plastic substrates to cut out a portion of the red light that is undesirable in color reproduction of color films. The object of the present invention is to provide a camera filter that provides excellent photographic color reproduction of green and dark green.

An embodiment of this invention will be described below with reference to the drawings.

FIG. 1 shows a cross-sectional view of the filter of the present invention, in which a vapor deposited film 2 is formed on one surface of an optical glass, plate glass, or plastic substrate 1, and an antireflection film 3 is formed on the other surface. The frame 4 is fitted into a frame body consisting of a rear frame 5 and a ring 6 in preparation for attachment to and detachment from the camera.

As shown in Figure 2, the above filter transmits blue light and green light and cuts out a portion of red light.If this filter is placed in front of the camera lens, it will remove the strong reflection of red light caused by organic dyes. This means that the color film is not exposed to unnecessary light. The spectral sensitivity distribution differs depending on the type of color film, and the spectral reflectance curve also differs depending on the type of organic dye, so the spectral transmittance of the filter that cuts out the red light area depends on the difference in these combinations. The curves will also be different. In other words, the dotted line A in Figure 2 is the spectral transmittance curve of the filter that cuts out the shortest wavelength among these combinations, and indicates the wavelength at which the transmittance is 50%.
It is 640nm. A filter that cuts out wavelengths shorter than this would cut out too much red light and disrupt the color balance, so this is the spectral transmittance curve of the filter that is at its limit on the shorter wavelength side. Also the second
The solid line B in the figure is the spectral transmittance curve of the filter that cuts out the longest wavelength among the above combinations, and the wavelength at which the transmittance is 50% is 700 nm. A filter that cuts out wavelengths longer than this can remove the reflection of red light, but the spectral transmittance curve of the filter reaches its limit on the longer wavelength side without achieving any significant effect as a filter.

Obtaining an arbitrary spectral transmittance curve within this range is impossible with glass filters, plastic filters, and gelatin filters, and it is necessary to use optical glass, plate glass, or plastic as a substrate and vacuum evaporate it on one side. Therefore, it is necessary to form a multilayer deposited film. In the above embodiment, a single layer or multilayer anti-reflection film 3 is deposited on one side of the substrate and formed on the other side by vacuum deposition, but it is important to minimize the prevention of ghosts and flares caused by photography. It becomes possible to keep it at .

As described above, according to this invention, by forming a vapor-deposited film on one side of optical glass, plate glass, or plastic, blue light and green light are transmitted, and a part of red light is cut out. This has the effect of removing reflections and improving color reproduction in color photographs.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the filter of the present invention, Figure 2 is the spectral transmittance curve of the same filter, Figures 3 and 4 are the spectral transmittance curves of the red transmission filter and cyan filter, and Figure 5 is the spectral tristimulus values. Diagram, Figure 6 is the spectral sensitivity curve of color film,
FIG. 7 is a spectral reflectance curve of green fabric. 1: Filter, 2: Deposited film, 3: Anti-reflection film, 4: Front frame, 5: Rear frame, 6: Stop ring.

Claims (1)

[Scope of utility model registration request] A vapor-deposited film is formed on optical glass, plate glass, or a plastic substrate that transmits blue light and green light and cuts a portion of red light sharply from 640 nm to 700 nm in the wavelength range showing 50% transmittance, and this is used as a camera. A camera filter that is fitted into a removable frame.