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.

Image (sensor) Size Crop factor Wide Angle Standard Medium
5 x 4 inch 0.3 80mm 150mm  
645 MF 0.625 45mm 80mm  
35mm Film 1 28mm 50mm  
APS-C (Nikon) 1.5 17mm 35mm 80mm
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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