Normal lens for DX format cameras
What is the Normal Lens for digital?
I posted my ideas on DPR in the early days about this and was soundly slapped down. But I think cooler heads prevail now, and it may be safe to revisit my idea, (which isn't 'mine' actually - just theory as I know it):
What is a "Normal" lens? It is the lens which produces a view similar to an "eye view" of a given scene, ie "1:1" - no magnification or reduction. A lens with an f/l smaller than this becomes 'wide angle', larger - tele.
How is the "Normal lens" focal length determined? From the film/sensor FORMAT.
The so called 'normal' lens for ANY GIVEN FORMAT is roughly equiv to the film's (or sensor's) DIAGONAL. Thus for 35mm FILM it comes out around 46mm, for which the 50m lens is close.
With an APS-C sensor size of 23.6 x 15.7 mm, we would get a diagonal of (about) 28.6mm, which SHOULD be the "Normal" lens for any APS-C sensor based camera.
The 50mm as holy grail standard got entrenched, IMHO, from the early days when not many choices of lenses were available, and most cams, including Cartier-Bresson's Leica, CAME with a 50mm lens. So...
And, as another poster said, the "35mm equivalence" thing got started in the days when most people using digital were coming from 35mm film, and it made sense then. Now - I doubt may DSLR users have ever SEEN a 35mm cam, let along shot with one. So while I've always thought the '35mm equiv' thing was more confusing than helpful, I can now, when there are so many different digital sensor sizes, a common-base reference and if called "Standard Equivalence" or the like, could be helpful.
So now I have to take my 16mm-70mm lens on the DX 5100, set to 28mm and compare images to those on FX taken with an FX 50mm lens... Do you think they will be close to each other, lens quality aside?
Who was Ansel Adams' Ansel Adams?