6x7 film crop factor and field of view calculator
A 6x7 film sensor measures 56 by 70 mm, a diagonal of 89.64 mm. Against the full-frame diagonal of 43.27 mm that is a crop factor of 0.483.
The diagonal divided by this gives the acceptable blur circle. 1500 is the usual modern figure.
- Full-frame equivalent focal length
- 16.89
- Equivalent aperture for depth of field
- 1.351
- Sensor diagonal
- 89.644
- Sensor area
- 3920.00 mm2
- Full frame gathers this many times more light
- 0.220
- Horizontal field of view
- 77.320 degrees
- Vertical field of view
- 90.000 degrees
- Diagonal field of view
- 104.030 degrees
- Hyperfocal distance
- 7356
- Depth of field
- 2888
- Frame width at the subject
- 4.800
Show the working
- Focal length = 35
- Aperture f-number = 2.8
- Subject distance = 3
- Circle of confusion divisor = 1500
- sensor_w = 56 = 56
- sensor_h = 70 = 70
- Sensor diagonal = hypot(56, 70) = 89.6437
- Crop factor = 89.6437 > 0 ? 43.266615305567875 / 89.6437 : 0 = 0.482 651
- Full-frame equivalent focal length = 35 * 0.482 651 = 16.8928
- Equivalent aperture for depth of field = 2.8 * 0.482 651 = 1.351 42
- Sensor area = 56 * 70 = 3920
- Full frame gathers this many times more light = 3920 > 0 ? 864 / 3920 : 0 = 0.220 408
- Horizontal field of view = deg(2 * atan(56 / (2 * 35))) = 77.3196
- Vertical field of view = deg(2 * atan(70 / (2 * 35))) = 90
- Diagonal field of view = deg(2 * atan(89.6437 / (2 * 35))) = 104.03
- coc = 89.6437 / 1500 = 0.059 762 5
- Hyperfocal distance = 35^2 / (2.8 * 0.059 762 5) + 35 = 7355.65
- near = 3*1000 * 7355.65 / (7355.65 + (3*1000 - 35)) = 2138.14
- far = 3*1000 < 7355.65 ? 3*1000 * 7355.65 / (7355.65 - (3*1000 - 35)) : 1e9 = 5025.9
- Depth of field = 5025.9 >= 1e9 ? 1e9 : 5025.9 - 2138.14 = 2887.76
- Frame width at the subject = 35 > 0 ? 3 * 56 / 35 : 0 = 4.8
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- crop factor = full-frame diagonal / sensor diagonal
- field of view = 2 arctan(sensor dimension / 2 focal length)
- hyperfocal distance = f^2 / (N c) + f
- equivalent aperture = aperture x crop factor, for depth of field and total light
Crop factor changes the framing, not the lens. A 50 mm lens is always a 50 mm lens; it just sees a smaller rectangle.
Equivalent aperture matters for depth of field and total light gathered, not for exposure. An f/2.8 lens meters as f/2.8 on any format.
The circle of confusion is a judgement about acceptable sharpness at a viewing size, not a physical constant.
Equivalent focal lengths on 6x7 film
| Lens | Full-frame equivalent |
|---|---|
| 12 mm | 5.8 mm |
| 16 mm | 7.7 mm |
| 24 mm | 11.6 mm |
| 35 mm | 16.9 mm |
| 50 mm | 24.1 mm |
| 85 mm | 41.0 mm |
| 135 mm | 65.2 mm |
| 200 mm | 96.5 mm |
Frequently asked
What is the crop factor of a 6x7 film sensor?
0.483, calculated from its 89.64 mm diagonal against full frame at 43.27 mm.
Does a crop sensor make a lens longer?
No. The lens projects the same image; the smaller sensor simply records a smaller part of it, which looks like a longer lens.