Is 55mm on a dSLR the same 'reach' as 55mm on a PS?

[Contriver]

I have a Canon A520, its 35mm equivalent specsis 35-140mm. Would a, say, K100D with the lens kit (18-55) at 55mm give the same 'reach' as the A520 at 55mm?

[Bob Nichol]

The Pentax K100D has a 1.5 crop factor so the lens in question would have a 35mm effective focal length (EFL) of 27- 82mm. 55mm @ 35mm EFL would be around 37mm on the lens barrel markings. However the Pentax sensor has a 3:2 aspect ratio and the Canon sensor has 4:3 aspect ratio so you would get a slightly different view of the world through the two cameras. To put the aspect ratio in perspective, 4:3 is the aspect ratio for a standard computer monitor. A 3:2 aspect ratio image on a standard monitor would look somewhat letterboxed, for example a 4000x2666 pixel image on a 4000x3000 pixel monitor.

[Contriver]

Thank you for the very comprehensive answer Bob! So how doesthis translate to what you see with your own eyes? For example, at 55mm, willa subject appearcloser tothe camerathan what the human eye sees?

[Bob Nichol]

The K100D with the lens kit (18-55) at 55mm would be somewhat telelphoto with a 35mm EFL of about 82mm. (55mm x 1.5 = 82.5mm).

[eric s]

Just to add to Bob's comment.
With a film camera (35mm) the human eye sees basically like a 50mm lens.
So a 33mm lens on the K100D (with a 1.5x crop factor) would be roughly what the human eye sees.

Eric