Wide Angle Photography

[sentinel_au]

Before I continue, forgive me for being a novice...

Would this lenses EF-S 17-85mm f4-5.6 IS USM have a wider view than something like a EF 24mm f/2.8. And can you please explain why to me, cause i believe that the 24mm would be more wide angle, being a wide angle lense, but im not exactly sure why this would be the case...

[dwig]

the 17-85 zoom, when set to its wider settings, would give a more wide angle view than the 24mm fixed lens.

"Wide Angle" and "Telephoto" are very sloppily used terms in normal speach. There are technical definitions (note the plural) but a degree of understanding of the basis for the technical terms is necessary. Common usage gets sloppy as a result. "Wide Angle" can refer to the photographic effect or can refer to some optical properties of the lens. When refering to the lens's optical properties, it is a rough measure of how large an image diameter it will create, not how large objects will appear, relative to its focal lengh. The scientific definition of "telephoto" is completly different and more complicated.

For most real-world photographic usage, rather than laboratory physics type useage, where you are refering to the photographic effect, the follow "definitions" are reasonable:

1. "Normal" lens: a lens with a focal length (17mm, 24mm, 85mm, ...) equal to the diagonal of the "image receptor". We used to say "film" but now its often a CCD.

2. "Wide Angle" is any lens with a shorter focal length than normal.

3. "Telephoto" is any lens with a longer focal length.

With standard "old school" 35mm film photography, a 35 to 42mm lens is "normal" although the conventional standard lens on SLRs was often a 50mm lens but only for some mechanical reasons. Also, with 35mm photography, virtually every camera used exactly the same negative size (there were a few odd cameras that varied).

With digital cameras, the CCD imaging chip vary widely in side. Comparing the effect of a lens of a praticual focal length on one camera to than on another is complicated by this inconsistancy. As a result, many manufacturers of digital cameras mention the "35mm equivalent" to give you a basis for comparison.

dSLR's are a bit more consistanct in image chip size than the point&shoots, but still vary significantly. With these, the manufactures generally mention a "cropping factor" (terms vary somewhat) which gives you a way to calculate the 35mm equivalent of any given lens. The lenses can't be so marked because they can be used on different dSLR bodies that might have differing image chips.

On the same camera, the zoom you mention would be a wider angle lens than the fixed 24mm lens when it is zoomed to any focal lenght less than 24mm. If you are comparing the 17-85 on one camera to the 24mm on another, all bets are off. A Nikon CoolPix 8400's 6.1mm widest setting gives roughly the same "wide angle effect" as a 16mm lens on a D70 or a 24mm lens of my old Nikon F3 35mm film camera.

[sentinel_au]

Thankyou so much, that was the most informative reply I have ever read on a forum before. Many many thanks.