Variable-effect filtering device
Patent Information
- Application Number
- EP2023833762
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-19
- Filing Date
- 2023-12-18
- Publication Date
- 2025-10-29
AI Technical Summary
Cinematographers face limitations in modulating image rendering due to the need for consistent focal length range performance across sequences, with existing solutions risking texture visibility in bokeh or uneven rendering across the image field.
A filtering device with a variable effect, comprising a filter with a central and peripheral zone, and an adjustable diaphragm that modifies the accessible portion of the filtering zone, allowing for adaptable optical properties such as diffusion, polarization, or wavefront distortion to be applied to the image formed by a shooting lens.
Enables simple and rapid modification of image rendering by adjusting the diaphragm aperture, providing a consistent filtering effect across different focal lengths and lens types, while maintaining control over contrast and softness.
Smart Images
Figure 1.1
Abstract
Description
[0001] DESCRIPTION
[0002] TITLE: Variable effect filtering device
[0003] The present invention relates to a variable effect filtering device. The present invention also relates to an assembly comprising a shooting lens and such a filtering device. The present invention also relates to a method for modifying the rendering of an image using such a filtering device.
[0004] The present invention relates to the field of cinema, and of shooting in general.
[0005] In particular, in the field of cinematography, cinematographers choose their lenses according to the film they have to make, as well as their attachment to a particular family of lenses considered suitable for their lighting methods. Indeed, some lenses can be softer, i.e. have less contrast on intermediate frequency patterns (5 to 50 cy / mm), while having a good resolution (> 150cy / mm) for S35 to FF (full frame) sensors. Others, on the contrary, are considered hard because of their very good quality (or modulation transfer function) at intermediate frequencies. Thus, the choice of a specific contrast is made (in part) according to the choice of lenses.
[0006] However, this modularity is limited by the need to have a focal length range with the same performance for a given sequence.
[0007] Diffuser filters can be used on the front or back of the lens. However, there is a risk of seeing the texture of the diffuser in the bokeh (background blur) of the image.
[0008] It is also possible to move lenses to reduce contrast by spreading aberrations. However, the result is not that of a diffuser and is not the same across the entire field.
[0009] There is therefore a need for a device allowing the modification of the rendering of an image formed by a lens, in a simple and adaptable manner at any time.
[0010] For this purpose, the present description relates to a variable effect filtering device, comprising: a. a filter having a useful surface comprising a central zone and a peripheral zone surrounding the central zone, the filter having a predefined optical property over a zone, called the filtering zone, the filtering zone being the central zone or the peripheral zone or the entire useful surface, and b. a diaphragm having an adjustable opening between the full opening of the diaphragm and the maximum closure of the diaphragm, the diaphragm being positioned relative to the filter so that the full opening of the diaphragm corresponds to the useful surface of the filter and that the modification of the opening of the diaphragm modifies the accessible portion of the filtering zone or the accessible portion of another zone of the useful surface, making it possible to induce a modification of the filtering effect.
[0011] Depending on specific implementation methods, the device includes one or more of the following characteristics, taken in isolation or in all technically possible combinations:
[0012] - the filtering area is the central area or the peripheral area, the predefined optical property being uniform over the filtering area.
[0013] - the predefined optical property presents a progressive radial variation over the filtering zone.
[0014] - the full opening of the diaphragm delimits the peripheral zone of the filter.
[0015] - the filtering zone and the opening formed by the diaphragm have roughly the same shape, except for a homothety.
[0016] - the central area has a shape chosen from one of the following: circular, square, rectangular, parallelepiped, triangular, oval, and star-shaped.
[0017] - the predefined optical property is chosen from one of the following properties: a diffusion property, a polarization property, a colorimetric property, a wavefront deformation property, a transparency property and a combination of at least two of the preceding properties.
[0018] - the filtering zone is the central zone or the peripheral zone, the useful surface of the filter comprising at least one intermediate zone surrounding the central zone and surrounded by the peripheral zone, the at least one intermediate zone comprising a radial progressive variation of the predefined optical property between the central zone and the peripheral zone.
[0019] - the diaphragm is an iris diaphragm.
[0020] The present description also relates to an assembly comprising: a. a shooting object, and b. a filtering device, the device being positioned substantially in the pupil of the shooting lens, allowing the modification of the rendering of an image formed by the shooting lens.
[0021] The present description also relates to a method for modifying the rendering of an image formed by a shooting lens, the method comprising: a. positioning a filtering device as described above substantially in the pupil of the shooting lens, and b. modifying the aperture of the diaphragm so as to modify the accessible portion of the filtering zone or the accessible portion of another zone of the useful surface so as to induce a modification of the filtering effect, allowing the modification of the rendering of an image formed by the shooting lens.
[0022] Other characteristics and advantages of the invention will appear on reading the following description of embodiments of the invention, given by way of example only and with reference to the drawings which are:
[0023] [Fig. 1], figure 1, a schematic representation of an assembly comprising a shooting lens and a filtering device,
[0024] [Fig. 2], figure 2, a schematic representation of a filtering device according to a first embodiment, the diaphragm of the filtering device being fully open,
[0025] [Fig. 3], Figure 3, a schematic representation of the filtering device of Figure 2, the diaphragm of the filtering device being at an intermediate opening,
[0026] [Fig. 4], Figure 4, a schematic representation of the filtering device of Figure 2, the diaphragm of the filtering device being at yet another intermediate opening,
[0027] [Fig. 5], Figure 5, a schematic representation of a filtering device according to a second embodiment, the diaphragm of the filtering device being at an intermediate opening,
[0028] [Fig. 6], Figure 6, a schematic representation of the filtering device of Figure 5, the diaphragm of the filtering device being at another intermediate opening, and
[0029] [Fig. 7], Figure 7, a schematic representation of a filtering device according to a third embodiment, the filtering zone extending over the entire useful surface of the filter.
[0030] A shooting lens 10 and a filtering device 12 are illustrated in FIG. 1.
[0031] The shooting lens 10 is capable of forming an image of a scene on a sensor. The shooting lens 10 is, for example, a camera or cinema lens or zoom. The shooting lens 10 typically comprises at least one lens, and conventionally a set of lenses.
[0032] The filtering device 12 is capable of generating a variable filtering effect. By the term “variable”, it is understood that the filtering is made to vary according to the configuration (settings) of the filtering device 12. The adjustment can be easily carried out in less than one second. The filtering device 12 is intended to be positioned substantially in the pupil of the shooting lens 10 (as is the case in FIG. 1), for modifying the rendering of an image formed by the shooting lens 10. By the term “substantially”, it is understood “near” or more precisely at a distance less than a predetermined distance from the pupil. The predetermined distance is, for example, equal to 2 mm.
[0033] The filtering device 12 comprises a filter 20 and a diaphragm 22.
[0034] Filter 20 is a flat optical filter. Filter 20 is, for example, made of a material such as glass or plastic.
[0035] As illustrated in the examples of Figures 2 to 6, the filter 20 comprises a useful surface 23 comprising a central zone Z c and a peripheral zone Z P surrounding the central zone Zc. In the examples of Figures 2 to 6, the useful surface 23 extends over the entire surface of the filter 20. Alternatively, the useful surface 23 extends over only a portion of the filter 20.
[0036] Preferably, the surface of the central zone Z c is at least equal to 30 percent of the area of the peripheral zone Z P .
[0037] Preferably, the central zone Zc has a shape chosen according to the desired rendering. The shape of the central zone Zc is, for example, chosen from one of the following shapes: circular, square, rectangle, parallelepiped, triangular, oval and star-shaped. More generally, the shape of the central zone Z cis any shape achievable by an adjustable aperture diaphragm, such as an iris diaphragm.
[0038] In the examples of Figures 2 to 6, the central zone Z c is circular.
[0039] Filter 20 has a predefined optical property on only one of the central zone Z c and the peripheral zone Z P , called the filtering zone. The other zone thus has a different optical property.
[0040] For example, in the embodiment of Figures 2 to 4, the filtering area is the central area Z c , whereas in that of figures 5 and 6, the filtering zone is the peripheral zone Z P .
[0041] Preferably, the predefined optical property is selected from one of the following properties: a diffusion property (diffusing filtering area and other non-diffusing area), a polarization property (polarized filtering area and other non-polarized area), a colorimetric property (colored filtering area and other non-colored area), a wavefront deformation property, a transparency property (transparent filtering area and other opaque or partially transparent area), an opacity property (opaque or partially transparent filtering area and other transparent area) and a combination of at least two of the preceding properties. The value of the optical property is adapted according to the desired rendering. In an exemplary implementation, the predefined optical property is uniform over the filtering area.
[0042] Alternatively, the predefined optical property exhibits a radial variation over the filtering area. The variation is thus progressive and radially continuous. For example, in the case of a diffusing property, the diffusion increases from the center of the filtering area to the periphery of the filtering area, or vice versa.
[0043] In an optional embodiment, the filter 20 further comprises an intermediate zone surrounding the central zone Z c and surrounded by the peripheral zone Z P The intermediate zone comprises a progressive (radial) variation of the predefined optical property between the central zone Zc and the peripheral zone Z P This avoids a discontinuous variation of the optical property between the central zone Z c and the peripheral zone Z P , especially in the case where the optical property is uniform over the filtering area.
[0044] The diaphragm 22 has an adjustable aperture between the full opening of the diaphragm 22 and the maximum closure of the diaphragm 22.
[0045] Preferably, the aperture is continuously adjustable between the fully open diaphragm 22 and the maximum closure of the diaphragm 22. The adjustment is, for example, carried out by an adjustment mechanism. The diaphragm 22 is, for example, an iris diaphragm.
[0046] The diaphragm 22 is positioned relative to the filter 20 so that:
[0047] - the full opening of the diaphragm corresponds to the useful surface 23 of the filter 20, and the modification of the opening of the diaphragm 22 modifies the accessible portion of the filtering zone or the accessible portion of another zone of the useful surface 23, making it possible to induce a modification of the filtering effect. In other words, this modifies the accessible proportion of the filtering zone compared to the other zone (i.e. the ratio between the unobstructed portion of the filtering zone and the unobstructed portion of the other zone). By the term "accessible", it is understood accessible for an optical or "useful" flow.
[0048] Preferably, the accessible portion of the filtering zone or the accessible portion of another zone of the useful surface 23 is modified radially when modifying the opening of the diaphragm 22. In the examples of FIGS. 2 to 6, both the accessible portion of the filtering zone and the accessible portion of the other zone are suitable for being modified radially. By the term "radially", it is understood in the plane of the filter 20 and perpendicular to an axis passing substantially through the center of the central zone Z cand substantially perpendicular to the plane of the filter 20. The axis considered is the optical axis of the shooting lens 10 when the filtering device 12 is substantially positioned in the pupil of the shooting lens 10. In this case, the filtering device 12 is positioned relative to the shooting lens 10 so that the filter 20 is positioned substantially perpendicular to the optical axis of the shooting lens 10 and the center of the central zone Zc of the filter 20 is substantially on the optical axis of the shooting lens 10.
[0049] Preferably, the aperture of the diaphragm 22 is centered on the center of the central zone Z c .
[0050] Preferably, the full opening of the diaphragm 22 delimits the peripheral zone Z P of filter 20.
[0051] Preferably, the maximum closure of the diaphragm 22 completely closes the central zone Z c and the peripheral zone ZP of filter 20.
[0052] Preferably, the central zone Zc and the opening formed by the diaphragm 22 have substantially the same shape (within a homothety). In the examples of Figures 2 to 6, the central zone Zc and the opening thus have a circular shape.
[0053] A method of modifying, via the filtering device 12, the rendering of an image formed by the shooting lens 10, will now be described.
[0054] The filtering device 12 is positioned relative to the shooting lens 10 so as to be substantially in the pupil of the shooting lens 10. The filtering device 12 is preferably positioned so that the optical axis of the shooting lens 10 passes through the center of the central zone Z c of filter 20 and is perpendicular to the plane of filter 20.
[0055] The aperture of the diaphragm 22 is then modified so as to radially modify the accessible portion of the filtering zone or the accessible portion of another zone of the useful surface 23, allowing the modification of the rendering of an image formed by the shooting lens 10. Typically, when the property is a diffusing property, depending on the aperture of the diaphragm 22, the image is made more or less blurred (“softness” effect). Thus, by opening or closing the diaphragm 22, for example by simply rotating a ring, it is possible to significantly modify the characteristics of the image which will be formed by the lens.
[0056] In the embodiment of Figures 2 to 4, only the central zone Z chas a diffusing property. Such a property makes it possible to modify the contrast of the image (the image is softened even more as light is allowed to pass through a diffusing zone). In the case of Figure 2, the diaphragm 22 is at full aperture, which means that approximately 14% of the pupil is diffused. In Figure 3, the aperture of the diaphragm 22 is intermediate (T3.6) while still allowing a portion of the peripheral zone Z to appear P , which means that about 40% of the pupil is diffused. In Figure 4, the aperture of diaphragm 22 is intermediate (T5.6) and completely masks the peripheral zone Z P , which means that 100% of the pupil is diffused.
[0057] In the embodiment of Figures 5 and 6, only the peripheral zone Z P has a diffusing property. In the case of Figure 5, the diaphragm 22 is at an intermediate opening, still allowing a portion of the peripheral zone Z to appear.P , which makes the pupil diffusion apparent. In the case of Figure 6, the diaphragm 22 completely masks the peripheral zone Z P , which makes the pupil undiffused.
[0058] Thus, the filtering device 12 makes it possible to modify, simply and quickly, the rendering of an image formed by a shooting lens 10. The adjustment is carried out outside the lens, and can be carried out at any time, for example via the rotation of a ring of the diaphragm 22 which allows it to be opened or closed.
[0059] Such an optical filter is, moreover, inexpensive and simple to produce. For example, in the case of diffusion, the filter can be composed of a plastic film (Mitchel filter) glued between two plates or by a plate frosted in the desired surfaces, or by a holographic diffuser, or by gluing a grid, or any other diffusion principle.
[0060] Furthermore, it should be noted that the present invention makes it possible to obtain the same filtering effect, for the same aperture of the diaphragm 22 and for lenses of the same series, but of different focal lengths, on the condition of adapting the dimensions of the filter 20 (accessible portion of the center zone Z c and the peripheral zone Z P notably).
[0061] Although the examples in the description have highlighted the diffusion properties, the invention applies to all types of optical properties making it possible to modify the rendering of an image formed by a lens depending on the opening of a diaphragm.
[0062] Furthermore, it is noted that the filtering device is not limited to the case where the filtering zone extends over only one of the central zone Zc or the peripheral zone Z P. Indeed, in an alternative implementation illustrated in Figure 7, the filtering zone extends over the entire useful surface 23 of the filter 20. In this case, the modification of the opening of the diaphragm 22 only modifies the accessible portion of the filtering zone (and not another zone of the useful surface 23 since the filtering zone occupies the entire useful surface 23). Preferably, the predefined optical property has a continuous progressive variation (radial) over the filtering zone. For example, in the case of a diffusing property, the diffusion increases from the center of the useful surface 23 (central zone) towards the periphery of the useful surface 23 (peripheral zone), or vice versa. The other characteristics described previously, in particular for the embodiments of Figures 2 to 6, also apply to this additional embodiment.More generally, those skilled in the art will understand that the embodiments and variants previously described can be combined with each other provided that they are technically compatible.
Claims
CLAIMS 1. Variable effect filtering device (12), comprising: - a filter (20) having a useful surface (23) comprising a central zone (Z c ) and a peripheral zone (Z P ) surrounding the central zone (Z c ), the filter (20) having a predefined optical property over an area, called the filtering area, the filtering area being the central area (Z c ) or the peripheral zone (Z P ) or the entire useful surface (23), and - a diaphragm (22) having an adjustable opening between the full opening of the diaphragm (22) and the maximum closure of the diaphragm (22), the diaphragm (22) being positioned relative to the filter (20) so that the full opening of the diaphragm corresponds to the useful surface (23) of the filter (20) and that the modification of the opening of the diaphragm (22) modifies the accessible portion of the filtering zone or the accessible portion of another zone of the useful surface (23), making it possible to induce a modification of the filtering effect.
2. Device (12) according to claim 1, in which the filtering zone is the central zone (Z c ) or the peripheral zone (Z P ), the predefined optical property being uniform over the filtering area.
3. Device (12) according to claim 1, in which the predefined optical property has a progressive radial variation over the filtering zone.
4. Device (12) according to any one of claims 1 to 3, in which the full opening of the diaphragm (22) delimits the peripheral zone (Z P ) of the filter (20).
5. Device (12) according to any one of claims 1 to 4, in which the filtering zone and the opening formed by the diaphragm (22) have substantially the same shape, except for a homothety.
6. Device (12) according to any one of claims 1 to 5, in which the central zone (Zc) has a shape chosen from one of the following shapes: circular, square, rectangular, parallelepiped, triangular, oval, and star-shaped.
7. Device (12) according to any one of claims 1 to 6, in which the predefined optical property is chosen from one of the following properties: a property of diffusion, a polarization property, a colorimetric property, a wavefront deformation property, a transparency property, and a combination of at least two of the preceding properties.
8. Device (12) according to any one of claims 1 to 7, in which the filtering zone is the central zone (Z c ) or the peripheral zone (Z P ), the useful surface (23) of the filter (20) comprising at least one intermediate zone surrounding the central zone (Z c ) and surrounded by the peripheral zone (Z P ), the at least one intermediate zone comprising a radial progressive variation of the predefined optical property between the central zone (Z c ) and the peripheral zone (Z P ).
9. Device (12) according to any one of claims 1 to 8, wherein the diaphragm (22) is an iris diaphragm.
10. Assembly comprising: a. a shooting lens (10), and b. a filtering device (12) according to any one of claims 1 to 9, the device (12) being positioned substantially in the pupil of the shooting lens (10), allowing modification of the rendering of an image formed by the shooting lens (10).
11. Method for modifying the rendering of an image formed by a shooting lens (10), the method comprising: a. positioning a filtering device (12) according to any one of claims 1 to 10 substantially in the pupil of the shooting lens (10), and b. modifying the opening of the diaphragm (22) so as to modify the accessible portion of the filtering zone or the accessible portion of another zone of the useful surface (23) so as to induce a modification of the filtering effect, allowing the modification of the rendering of an image formed by the shooting lens (10).