Hyperfocal Cameras

9/29/2000

The idea is to choose a focusing distance, such that, the maximum amount is in focus at one time. In practice this means from infinity to some defined near focus point. There are a large number of factors that influence this number, focal length, film format, f-stop, etc.

One could use a normal photographic lens set to a hyperfocal distance and proceed, but this looses the "look and feel" of the pinhole camera. So, even though we are going to use a lens in this case instead of a pinhole, it would be nice to maintain as much of the aesthetic as possible.

 


50mm 2 element achromat @ F128 on Ilford Technical Film, Ortho, 4x5

I have been investigating using simple lenses for use in hyperfocal cameras. The simplest is a plano-convex lens. Curved on one side and flat on the other. These can be had from Edmund Scientific for under $20 [order their Industrial Optics catalog]. The next step up would be a two element acromatic lens, cost about $30-40. This offers superior color correction, but is unnecessary if we use ortho film or a colored filter.

Other possibilities include older lenses. I made one camera from a Zeiss Anastigmat, 75 mm, from 1891, found on a junk bench at a camera store. Don't overlook parts of lenses either. Taking apart an old 8mm movie camera will yield lots of fine optics.


Zeiss Anastigmat (made in 1891), f128 2 seconds with 23a filter onto T-Max 100

The easiest to use format for making these cameras is the 4x5. Flim can be had from Freestyle Camera for very little money. The only other supplies are a few film holders [used from swap meets or often in camera stores] and some black foam core board from an art supply store to make the camera itself out of. The camera is made in very much the same was as for a pinhole. [see making a 4x5 foam core pinhole camera]

Hyperfocal cameras work best in wide angle lengths. The advantage of a hyperfocal camera over a pinhole is more light and sharper focus. The disadvantage is more light and limited focus range. In a pinhole camera you do not need to worry about focus at all. In a hyperfocal, there is a minimum focus. For a 50mm lens [extreme wide angle for a 4x5], the minimum focus is 1/2 foot. Not so bad. But by the time you get to 150mm [normal lens for a 4x5] it is now closer to 4 feet. Not so good if you are used to a pinhole camera.

Another factor is the positioning of the lens. In a pinhole camera, if you are off a couple of millimeters, so what. But in a hyperfocal camera, even a fraction of a mm off will ruin the effect.

The size of the F-stop is less of a problem, even though the table looks scary. If you are off a little bit here, it usually means just making some adjustment in the exposure. One source of F-stops are those electron microscope grids mentioned in the pinhole section [see suppliers]

If you want to see the math involved in generating these tables, see Hyperfocal Math [also useful if you want to use an existing lens on a 35mm - 8x10 camera, as a hyperfocal lens]

NOTE: Simple lenses, though a lot less expensive, are not the same as expensive large format lenses. Without all the corrections of the higher priced lenses, the simple 1-3 element lenses project a different kind of image. Space is not flat, but rather curved. The area of sharpest focus will be different at the center of the image than at the edges. If a lens does not "work" for you in one orientation, try flipping it over, so the curved side is towards the subject or now towards the film. Like the artistic "Holga" camera users, do not be afraid to experiment and see in a different way.


Hard Contact lens, +13 diopter (77mm) behind a diaphragm from Edmund scientific. f128 1/2 second on Ilford Technical Ortho film (4x5). [lens was ordered from my optometrist, about $70]. Actual image is much sharper than appears here. Right is a closeup of the birds on the rock in the center. Note: this lens must be used stopped down. Wide open it is REALLY bad! Might make a good portrait lens, where one could control the amount of unsharpness by the aperature. Below is a lens image of the contact lens mounted behind a diaphragm. Contact lens faces the film, diaphragm to the outside. Actual size of lens is about 1/2 inch in diameter.

Tables: [4x5 camera]

Lens extension, mm

FL (mm)

F90

F128

50

58

62

55

63

67

60

68

71

65

73

76

70

77

81

75

82

86

80

87

91

85

92

96

90

97

101

95

102

106

100

107

111

105

112

116

110

117

121

115

122

125

120

127

130

125

132

135

130

137

140

135

142

145

140

147

150

145

152

155

150

157

160

FOCUS: [in feet!]

 

Focus camera at:

Near Limit of Focus

FL (mm)

F90

F128

F90

F128

50

1.2

0.9

0.6

0.4

55

1.5

1.0

0.7

0.5

60

1.7

1.2

0.9

0.6

65

2.1

1.4

1.0

0.7

70

2.4

1.7

1.2

0.8

75

2.7

1.9

1.4

1.0

80

3.1

2.2

1.6

1.1

85

3.5

2.5

1.8

1.2

90

3.9

2.8

2.0

1.4

95

4.4

3.1

2.2

1.5

100

4.9

3.4

2.4

1.7

105

5.4

3.8

2.7

1.9

110

5.9

4.1

2.9

2.1

115

6.4

4.5

3.2

2.3

120

7.0

4.9

3.5

2.5

125

7.6

5.3

3.8

2.7

130

8.2

5.8

4.1

2.9

135

8.9

6.2

4.4

3.1

140

9.5

6.7

4.8

3.3

145

10.2

7.2

5.1

3.6

150

10.9

7.7

5.5

3.8

Size of F-stop (mm):[lens extension taken into account]

FL (mm)

F90

F128

50

0.64

0.48

55

0.70

0.52

60

0.75

0.56

65

0.81

0.60

70

0.86

0.63

75

0.92

0.67

80

0.97

0.71

85

1.03

0.75

90

1.08

0.79

95

1.14

0.83

100

1.19

0.86

105

1.25

0.90

110

1.30

0.94

115

1.36

0.98

120

1.41

1.02

125

1.47

1.06

130

1.52

1.10

135

1.58

1.14

140

1.63

1.17

145

1.69

1.21

150

1.75

1.25