Patent US3732793A successfully refreshed from Google Patents.
US3732793A
Expired / Lapsed
US
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Calibrated variable neutral density filter for a camera
Assignee: Individual
•
Filing: 1971-10-26
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Granted: 1973-05-15
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Expires: 1991-10-26
Abstract
Abstract A calibrated neutral density filter has two polarizing filter members mounted in filter ring supports for rotation relative to one another. Indicia on the filter supports relate the degree of rotation of the two polarizing filter members relative to each other as a function of f:stop. An outer concentric ring mounted for rotation over the filter support has indicia printed thereon corresponding to f:stop graduations on the filter support. A reference point on the filter support indicates the f:stop correction necessary because of reduction of intensity of light through the two polarizing filter members. Setting of a predetermined f:stop reading on the concentric ring to the reference point indicates the corrected f:stop reading for the camera for any degree of rotation of the polarizing filters relative to each other.
Inventors
- 👤 P Tague
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 08:28
CPC Classifications
G; G03; G03B; G03B33/00; G02; G02B; G02B27/00; G02B27/28; G02B27/281; G03B17/00; G03B17/02; G03B17/12
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
179 words
A calibrated variable neutral density filter adapted to be secured over the lens of a camera, comprising: a first filter ring support having a polarizing filter member mounted therein, the filter ring support adapted to be secured to the lens of a camera, a second filter ring support rotatably secured to the first support having a polarizing filter member mounted therein, indicia on the first and second filter supports relating the degree of rotation of the two polarizing filter members relative to each other as a function of f:stop, an outer concentric ring mounted for rotation over the first filter support having indicia thereon corresponding to the f: stop readings on the first filter support, and a reference point on the first filter support indicative of the f:stop correction necessary because of reduction of light intensity through the two polarizing filters; whereby setting of a predetermined f:stop on the outer ring to the reference point indicates the correct f:stop reading to be set on the camera for any degree of rotation of the polarizing filters relative to each other.
Claim 2
Dependent Claim
179 words
A calibrated variable neutral density filter adapted to be secured over the lens of a camera, comprising: a first filter ring support having a polarizing filter member mounted therein, the filter ring support adapted to be secured to the lens of a camera, a second filter ring support rotatably secured to the first support having a polarizing filter member mounted therein, indicia on the first and second filter supports relating the degree of rotation of the two polarizing filter members relative to each other as a function of f:stop, an outer concentric ring mounted for rotation over the first filter support having indicia thereon corresponding to the f: stop readings on the first filter support, and a reference point on the first filter support indicative of the f:stop correction necessary because of reduction of light intensity through the two polarizing filters; whereby setting of a predetermined f:stop on the outer ring to the reference point indicates the correct f:stop reading to be set on the camera for any degree of rotation of the polarizing filters relative to each other.
Claim 3
Dependent Claim
113 words
The filter of claim 1 wherein the first filter support includes (a) an annular body having an extended flange threaded on the outer circumference thereof for securing to a conventional adapter ring, (b) an inner circumferential recess for receiving the polarizing filter, (c) retaining means disposed in the recess to retain the polarizing filter; wherein the second filter support includes (a) a second annular body mounted for rotation within the first annular body, (b) a circumferential recess therein for receiving a polarizing filter, (c) retaining means disposed in the recess to retain the polarizing filter and (d) an outwardly extending flange threaded on the inner circumference thereof for securing a lens attachment thereto.
Claim 4
Independent Claim
207 words
A method of employing a calibrated neutral density filter in taking photographs, the neutral density filter including (1) a first filter ring support having a polarizing filter member mounted therein, (2) a second filter ring support rotatably secured to the first filter support having a polarizing filter member mounted therein, (3) indicia on the first and second filter supports relating the degree of rotation of the two polarizing filter members relative to each other as a function of f:stop, (4) an outer concentric ring mounted for rotation over the first filter support having indicia thereon corresponding to the f:stop readings on the first filter support, and (5) a reference point on the first filter support indicative of the f: stop correction necessary because of reduction of light intensity through the two polarizing filters, the method comprising: a. obtaining an f:stop reading for the particular shutter speed desired, b. adjusting the outer concentric ring of the filter so that the f:stop reading obtained is set opposite the reference point, c. rotating the second polarizing filter relative to the first to a desired position, and (d) setting the camera to the corrected f:stop reading on the outer concentric ring for the degree of rotation of the second polarizing filter.
Claim 5
Independent Claim
207 words
A method of employing a calibrated neutral density filter in taking photographs, the neutral density filter including (1) a first filter ring support having a polarizing filter member mounted therein, (2) a second filter ring support rotatably secured to the first filter support having a polarizing filter member mounted therein, (3) indicia on the first and second filter supports relating the degree of rotation of the two polarizing filter members relative to each other as a function of f:stop, (4) an outer concentric ring mounted for rotation over the first filter support having indicia thereon corresponding to the f:stop readings on the first filter support, and (5) a reference point on the first filter support indicative of the f: stop correction necessary because of reduction of light intensity through the two polarizing filters, the method comprising: a. obtaining an f:stop reading for the particular shutter speed desired, b. adjusting the outer concentric ring of the filter so that the f:stop reading obtained is set opposite the reference point, c. rotating the second polarizing filter relative to the first to a desired position, and (d) setting the camera to the corrected f:stop reading on the outer concentric ring for the degree of rotation of the second polarizing filter.
References Cited (Backward Citations)
US2145914A
Cited
US2825271A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-05-14 | 1976-11-13 | 1977-05-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-05-14 | 1980-11-13 | 1981-05-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-05-14 | 1984-11-13 | 1985-05-15 | $7700.00 | Window Closed / Lapsed |