Originally posted by bdery No. Sorry, but no.
Focal length is a property of the lens. The focal length is related to the f-stop (f-stop is a ratio of aperture and focal length). It is also necessary to know the REAL focal length to properly set SR systems. The real focal length will also influence the depth of field (which is why getting a blurry background is difficult with a compact).
When you try to work around actual, measurable physical properties in order to make comparisons easier, you run around newer, much worse problems.The best thing is for people to understand how their sensor size influences field of view. It should actually be easier than to change how we measure focal length
I think FOV is much more usable. DOF is relative, its dependent on the sensor size and shooting distance in addition to the ratio.
The camera/engineer can set the SR system; engineers can do that. Its not a necessary item for the photographer.
Quote: The real focal length will also influence the depth of field (which is why getting a blurry background is difficult with a compact).
Because of the sensor size. No?
Its not correct to compare APS-C to FF with just a correction factor. A 77mm/f1.8 lens on FF doesn't become a 115mm/ f1.8 lens. Its becomes a 115mm f/2.5 lens with a f1.8 light gathering ability. BUT!, I think its preferable to know the FOV and light gathering ability; to me, 115mm f1.8 is more useful. Then, I remember that APS-C has ~ a stop less DOF than FF (from what I have read).
I'm not trying to confuse the OP. He's gotten his answer, the lens is 21mm, especially compared to his old Canon system. But its FOV (in 35mm terms), is 32mm, its speed is f/3.2. And its DOF is less than a 32mm f/3.2 would be. (due to framing, etc) Hopefully I don't have this wrong.