LESSON 13 · ALSO LESSON 20
Sensor sizes
Full frame, APS-C, Micro Four Thirds and the small sensors in phones: what the size changes, and what it does not.
FIVE SENSORS · ONE SCALE
- Full frame36 × 24 mm
- APS-C23.5 × 15.6 mm
- APS-C, Canon22.3 × 14.9 mm
- Micro Four Thirds17.3 × 13 mm
- 1/2.3-inch typeabout 30 mm²
Five rectangles drawn at the same scale: full frame 36 by 24 mm, two APS-C sizes, Micro Four Thirds, and the tiny 1/2.3-inch type.
The common sizes
Full frame is 36 × 24 mm, the size of a frame of 35 mm film. APS-C is typically 23.5 × 15.6 mm, or 22.3 × 14.9 mm on Canon. Micro Four Thirds images on 17.3 × 13 mm in a squarer 4:3 shape. Most compacts and phones use far smaller sensors; the common 1/2.3-inch type is about 30 mm².
Crop factor
Divide the full-frame diagonal by a sensor's diagonal and you have its crop factor. Multiply a lens's focal length by it to find the full-frame lens with the same view.
| Sensor | Crop factor |
|---|---|
| APS-C | 1.5 |
| APS-C, Canon | 1.6 |
| Micro Four Thirds | 2.0 |
More area, more light
At the same f-number and shutter speed every sensor makes an equally bright picture, but a larger one collects more light in total, in proportion to its area. Shown at the same size, its pictures have less noise.
Depth of field
Frame the same picture at the same f-number and the larger sensor gives the shallower depth of field. That is why small sensors are said to keep more in focus.
Try it today
- 01Find your camera's sensor size in its specifications.
- 02Work out its crop factor against 36 × 24 mm.
- 03Multiply your most-used focal length by it.
- 04Shoot a portrait wide open on your camera and on a phone.
- 05Compare how soft the two backgrounds are.
Figures from Wikipedia, 'Full-frame camera', 'APS-C', 'Micro Four Thirds system', 'Image sensor format' and 'Crop factor', read 2026.10.16. Crop factors are worked out from the sizes above; the 1/2.3-inch sensor is drawn at its stated area in a 4:3 shape. The steps under Try it today are working practice, not a standard.