A recent trip away to test a couple of cameras, and the shooting of one scene in particular, really brought home the meaning of those camera numbers.
Recently I combined the need to get away with the need to test a couple of cameras, specifically the Olympus E-3 and the Pentax K20D. The shooting of one particular scene really brought home to me the meaning of a couple of numbers.
The two images below were shot about a minute apart from roughly the same position (I was dodging waves, so there was some movement). One was with the Pentax K20D fitted with the Sigma 10-20mm zoom, shot at 10mm. The other was taken with the Olympus E-3 and the Zuiko 12-60mm zoom, at 12mm.
Now when you get to the wide-angle end of the focal length range, 2mm of focal length can make a significant difference to the field of view. On a 35mm film camera a 10mm lens has a field of view of 130 degrees, while the 12mm covers 122 degrees.
But another number that makes a huge difference here is the focal length multiplication factor. The Olympus has a 2.0x multiplication factor, whilst the Pentax has a 1.5x factor. That means the 12mm on the Olympus is effectively 24mm, while the 10mm on the Pentax is effectively 15mm, in 35mm terms. The field of view (FOV) of a 24mm has a FOV of 84 degrees with the 15mm covering 110 degrees, a huge difference.
So what does all this mean? Well, firstly you have to pay attention to the numbers when making any decisions involving cameras. Secondly system choices, especially sensor size, have huge implications for your actual picture taking. What should be an amazingly wide lens becomes only a moderately wide one on the Olympus system because of the tiny sensor. Of course sensor size has other implications, something I’ll be looking at in other articles.
