Turns out that telephoto refers to a specific construction of a long-focal-length lens, i.e., one where the lens is physically shorter than the focal length.
Is there a generic term for referring to lenses of long focal length, while being agnostic as to their optical construction, other than just "long lens"? (Wikipedia claims there's not.)
Alternately, is this distinction simply pedantry and I should just call all long lenses telephoto?
Firstly words, even technical terms, change meaning over time with usage. "Prime" originally meant the primary lens of a multi-lens cine camera. Now it means a lens with fixed focal length (sometime incorrectly called a fixed-focus lens). While we're on the subject, telephoto isn't even nearly the most incorrectly used term (that would almost certainly be HDR), people often confuse "depth of focus" with "depth of field", use "depth of field" to refer to "bokeh", use "bokeh" to refer to the degree of defocus in an image, the list goes on.
To answer your question, the only non-construction specific term to apply to a lens with a long focal length is simply "long". The distinction is not pedantry as it makes a big difference for large format photography, when using camera movements. Since the nodal point of a telephoto lens is in front of the optic rather than roughly in the middle, any lens tilts will require you to shift the lens again in order to restore the composition. Thus telephotos are more difficult to use and usually reserved for when size and weight are critical.
The only construction-agnostic term would be long lens to compliment the other lens classes: wideangle and normal.
The complimentary set to telephotos would be long-focus lenses:
Optical designs of telephoto lenses must contain a telephoto group, which allows the lens to be physically shorter than its focal length. A lens with a conventional design and a focal length longer than a normal lens should properly be referred to as long focus.
And from wikipedia:
A telephoto lens works by having the outermost (i.e. light gathering) element of a much shorter focal length than the equivalent long-focus lens ...
Long-focus lenses aren't used much anymore, at least in the SLR world, so you can basically just use telephoto to refer to longer focal lengths and not have to worry.
Well, to use Wikipedia as well, it would appear that the options are telephoto and long focus lenses. That means that "long focus" makes some sense as a general term, based on the explanation that telephoto lenses are designed to overcome some of the shortcomings of the latter. Having said that, I think telephoto has basically come to mean anything about 100mm or longer and nobody will be confused if you used the term generically for any long lens. Though, these days, I begin to wonder if anyone sees 100mm as telephoto now...
A tele lens consists of a tube attached to a camera at one end, and a lens (group) at the opposite end.
That makes for a rather long lens in that the lens (group) is a little further away then intended focal length, so that Aperture can be placed there where the optical lines cross.. i.e a 400mm tele lens will have the lens (group) a little more than 400mm away from the film (or sensor).
For example, lenses such as the Novoflex 400mm F5.6, Leitz Telyt (Leica) 400mm F6.3, Zeiss Tele Tessar (Hasselblad Series), and other such vintage lenses. Where as the ZEISS SONNAR ( Hasselblad series ) is a Long Focus lens.
Due to tele lens designs being long and slow, designers went a different route resulting in the long focus lens, which consists out of a tub_ with several lens (groups) divided throughout the tube, enabling designers to make corrections, improving on light gathering power (faster lenses), color rendition, curvature of field, coma,etc. In all, a better lens — although substantially heavier .
Compare the Sigma 400mm F5.6 (Long Focus) with the aforementioned Novoflex 400 F5.6 (Tele Lens) and one will see that the Sigma is physically a good deal shorter and smaller in diameter, yet of the same optical length and speed as the Novoflex.
Difference between Telephoto lens vs. Long Focus lens is Purely defined by their Construction. Both do the same job ( bring a distant object closer ) so without referring to construction they could be described as Tele lenses.
The word "tele" is older than Lenses; the words "long focus" came into being with lenses.
Hope this helps.
