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CROSS REFERENCE TO RELATED APPLICATION
Reference is made to and priority claimed from U.S. Provisional Application
Ser. No. US 60/003,238, filed 5 Sep. 1995, entitled DIFFERENTIAL
VIEWFINDER MASKS.
FIELD OF THE INVENTION
The invention relates generally to photography, and in particular to
viewfinders for cameras. More specifically, the invention relates to a
masking device for changing the aspect ratio of the field of view of the
viewfinder in a camera.
BACKGROUND OF THE INVENTION
When taking a picture it is necessary to know not only in what direction to
aim the camera but also how much of the subject will be included in the
picture. For this reason practically every camera has a viewfinder of some
kind.
Cameras have been proposed, such as disclosed in prior art U.S. Pat. No.
4,583,831, issued Apr. 22, 1986, that include means for taking pictures
which when printed are intended to have aspect ratios different than the
negatives. Each aspect ratio is selected by the photographer before he or
she takes the picture. One currently popular aspect ratio in addition to
the normal or full frame one, i.e. 1.5:1, in 35 mm photography is between
2:1 and 3:1. An aspect ratio between 2:1 and 3:1 provides a panoramic or
stretch format print as compared to the normal format print having an
aspect ratio of 1.5:1.
Since it is necessary for the photographer to know how much of the subject
will be included in the print, the viewfinder in these cameras typically
will have some masking device for partially masking the field of view of
the viewfinder to match the aspect ratio selected by the photographer. For
example, prior art U.S. Pat. No. 4,357,102, issued Nov. 2, 1982, suggests
manually inserting a pair of front and rear masks in the field of view of
the viewfinder to position respective larger and smaller openings of the
front and rear masks in the field of view to change the aspect ratio of
the field of view to the selected ratio. A problem, however, with this
approach is that the pair of masks may be lost since they are not built
into the camera.
SUMMARY OF THE INVENTION
A camera comprising viewfinder means for defining a field of view provided
with a given aspect ratio, and a pair of front and rear masks insertable
in the field of view to position respective larger and smaller openings of
the front and rear masks in the field of view to change the aspect ratio
of the field of view, is characterized in that:
differential means connects the front and rear masks for moving the front
mask a greater extent than the rear mask is moved, to position the larger
and smaller openings in the field view.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1, 2, and 3 are perspective views of a camera provided with a masking
device for a viewfinder according to a preferred embodiment of the
invention, showing the masking device in three different modes.
DETAILED DESCRIPTION OF THE INVENTION
The invention is disclosed as being embodied preferably in a camera.
Because the features of a camera are generally known, the description
which follows is directed in particular only to those elements forming
part of or cooperating directly with the disclosed embodiment. It is to be
understood, however, that other elements may take various forms known to a
person of ordinary skill in the art.
Referring to the drawings, FIG. 1 shows a camera 10 having a main body
portion 12. The main body portion 12 comprises a cartridge chamber 14, a
film exposure chamber 16, an unexposed film roll chamber 18, and a battery
chamber 20 to hold one or more batteries for a built-in electronic flash
22. This arrangement is similar to many commercially available single-use
cameras.
A viewfinder 24, shown in FIG. 1 in broken lines to be able to see an
otherwise hidden portion of the camera 10, includes a larger front lens 26
and a smaller rear eye-lens 28 for viewing a subject to be photographed.
The viewfinder 24 defines a field of view provided with an HDTV (high
density television) aspect ratio of 1.78:1. See FIG. 1.
A pair of front and rear masking blades 30 and 32 include two sets of
matching larger-front and smaller-rear openings 34, 36 and 38, 40. The
matching larger-front and smaller-rear openings 34, 36 of one set both
have a normal aspect ratio of 1.5:1. The matching larger-front and
smaller-rear openings 38, 40 of the other set both have a panoramic aspect
ratio of 2.85:1. The front and rear masking blades 30 and 32 are
individually supported to permit each set of the larger-front and
smaller-rear openings 34, 36 and 38, 40 to be separately aligned in the
field of view of the viewfinder 24 to change the aspect ratio of the field
of view from 1.78:1 to either 1.5:1 or 2.85:1 as shown in FIGS. 2 and 3.
To selectively move the front and rear masking blades 30 and 32 in opposite
directions 42 and 44 from respective locations in front of the cartridge
chamber 14 and behind the unexposed film roll chamber 18, as shown in FIG.
1, a first increment to align the set of matching larger-front and
smaller-rear openings 34, 36 in the field of view of the viewfinder 24, as
shown in FIG. 2, and a second increment to align the set of matching
larger-front and smaller-rear openings 38, 40 in the field of view, as
shown in FIG. 3, there is provided a differential gear mechanism. The
differential gear mechanism, as shown in FIG. 1, comprises respective
racks 46 and 48 formed on the front and rear masking blades 30 and 32,
corresponding pinions 50 and 52 rotatably supported in engagement with the
separate racks, a reduction gear 54 coaxially fixed to the pinion 50, and
a motion transmission gear 56 interconnecting the pinion 52 and the
reduction gear. Owing to this arrangement, the front mask 30 is moved a
greater extent than the rear mask 32 is moved to align each set of
matching larger-front and smaller-rear openings 34, 36 and 38, 40 in the
field of view of the viewfinder 24, as shown in FIG. 2 and 3.
Film encodement means such as a pair of light-emitting diodes (LED's) 58
and 60 aligned with respective apertures 62 and 64 are provided for
optically recording detectable encodements on a film section, not shown,
in the film exposure chamber 16 in accordance with whichever one of the
sets of matching larger-front and smaller-rear openings 34, 36 and 38, 40
are aligned in the field of view of the viewfinder 24. A third mask 66,
located between the two LED's 58 and 60 and the two apertures 62 and 64,
has a longitudinal rack 68 in engagement with a pinion 70 coaxially fixed
to the pinion 52. When the set of matching larger-front and smaller-rear
openings 34, 36 are aligned in the field of view of the viewfinder 24, as
shown in FIG. 2, respective openings 72 and 74 in the third mask 66 are
positioned between the LED's 58 and 60 and the apertures 62 and 64 to
permit the LED, s to expose a pair of dots (the equivalent of binary 1, 1)
on the film section in the film exposure chamber 16. When the set of
matching larger-front and smaller-rear openings 38, 40 are aligned in the
field of view of the viewfinder 24, as shown in FIG. 3, only the opening
74 in the third mask 66 is positioned between the LED 60 and the aperture
64 to permit only that LED to expose a dot (the equivalent of binary 0, 1)
on the film section in the film exposure chamber 16.
The invention has been described with reference to a preferred embodiment.
However, it will be appreciated that variations and modifications can be
effected by a person of ordinary skill in the art without departing from
the scope of the invention. For example, instead of using the two LED's 58
and 60 as film encodement means other equivalents such as magnetic heads
may be used. Also, in place of the two LED's 58 and 60 one LED that can
direct light through both of the apertures 62 and 64 will suffice.
PARTS LIST
10. camera
12. main body portion
14. cartridge chamber
16. film exposure chamber
18. unexposed film roll chamber
20. battery chamber
22. electronic flash
24. viewfinder
26. front lens
28. rear eye-lens
30. front masking blade
32. rear masking blade
34. larger-front opening
36. smaller-rear opening
38. larger-front opening
40. smaller-rear opening
42. direction
44. direction
46. rack
48. rack
50. pinion
52. pinion
54. reduction gear
56. motion transmission gear
58. LED
60. LED
62. aperture
64. aperture
66. third mask
68. rack
70. pinion
72. opening
74. opening
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