Focal Length Compared to Image Size

Focal Length Compared to Image Size

The apparent focal length of a lens on a digital camera is often compared to 35mm film camera. Many questions are asked about how this comparison is made, why the numbers are so different and what focal lengths are equivalent to wide angle & telephoto lenses on a film camera.

As the sensors on most digital cameras are smaller (in most cases MUCH smaller) than 35mm film their lenses have to have smaller focal lengths to give the same view as a 35mm film camera. The same is true with 35mm compared to medium format cameras.

Crop factor
Wide Angle
Standard
Medium Telephoto
5 x 4 inch
0.3
80mm
150mm
645 MF
0.625
45mm
80mm
35mm Film
1
28mm
50mm
80mm
APS-C (Nikon)
1.5
17mm
35mm
4/3 system (Olympus)
2
14mm
25mm
Digicam (2/3")
4
7mm
12.5mm
Small sensor digicam (1/3.6")
9
3mm
5.5mm

 

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Image sizing advice for digitally projected competitions by Kev Bell