APS-H crop factor and field of view calculator
A APS-H sensor measures 28.7 by 19 mm, a diagonal of 34.42 mm. Against the full-frame diagonal of 43.27 mm that is a crop factor of 1.257.
The diagonal divided by this gives the acceptable blur circle. 1500 is the usual modern figure.
- Full-frame equivalent focal length
- 44.00
- Equivalent aperture for depth of field
- 3.520
- Sensor diagonal
- 34.419
- Sensor area
- 545.30 mm2
- Full frame gathers this many times more light
- 1.584
- Horizontal field of view
- 44.587 degrees
- Vertical field of view
- 30.372 degrees
- Diagonal field of view
- 52.367 degrees
- Hyperfocal distance
- 19 101
- Depth of field
- 954
- Frame width at the subject
- 2.460
Show the working
- Focal length = 35
- Aperture f-number = 2.8
- Subject distance = 3
- Circle of confusion divisor = 1500
- sensor_w = 28.7 = 28.7
- sensor_h = 19 = 19
- Sensor diagonal = hypot(28.7, 19) = 34.4193
- Crop factor = 34.4193 > 0 ? 43.266615305567875 / 34.4193 : 0 = 1.257 04
- Full-frame equivalent focal length = 35 * 1.257 04 = 43.9965
- Equivalent aperture for depth of field = 2.8 * 1.257 04 = 3.519 72
- Sensor area = 28.7 * 19 = 545.3
- Full frame gathers this many times more light = 545.3 > 0 ? 864 / 545.3 : 0 = 1.584 45
- Horizontal field of view = deg(2 * atan(28.7 / (2 * 35))) = 44.5873
- Vertical field of view = deg(2 * atan(19 / (2 * 35))) = 30.3717
- Diagonal field of view = deg(2 * atan(34.4193 / (2 * 35))) = 52.3671
- coc = 34.4193 / 1500 = 0.022 946 2
- Hyperfocal distance = 35^2 / (2.8 * 0.022 946 2) + 35 = 19 101.3
- near = 3*1000 * 19 101.3 / (19 101.3 + (3*1000 - 35)) = 2596.9
- far = 3*1000 < 19 101.3 ? 3*1000 * 19 101.3 / (19 101.3 - (3*1000 - 35)) : 1e9 = 3551.24
- Depth of field = 3551.24 >= 1e9 ? 1e9 : 3551.24 - 2596.9 = 954.344
- Frame width at the subject = 35 > 0 ? 3 * 28.7 / 35 : 0 = 2.46
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 APS-H
| Lens | Full-frame equivalent |
|---|---|
| 12 mm | 15.1 mm |
| 16 mm | 20.1 mm |
| 24 mm | 30.2 mm |
| 35 mm | 44.0 mm |
| 50 mm | 62.9 mm |
| 85 mm | 106.8 mm |
| 135 mm | 169.7 mm |
| 200 mm | 251.4 mm |
Frequently asked
What is the crop factor of a APS-H sensor?
1.257, calculated from its 34.42 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.