Just for giggles, does anybody know whether a zoom lens has ever been manufactured for any system which is at its most compact not when maximally zoomed out or when maximally zoomed in (as e.g. Sony’s 24-50 f2.8) but at a medium focal length (e.g. somewhere between 35 and 50 mm for a standard zoom)?
Evidently I’m assuming an extending barrel design for the purposes of this question, since non-extending, internal zoom lenses are usually big, heavy and expensive. The reason I’m asking is because imho for functionality purposes, it would be kind of great to have a lens that is stored at a medium focal length to be used as the standard focal length, only zooming in or out when required.
I don’t know much of anything about lens design. I’m assuming that there would be some considerable compromises in terms of image quality etc. And yes, obviously it’s possible to set any zoom lens to a preferred “standard” focal length and only zoom in or out when required. This is actually how I try to use zooms now, trying to teach myself to use a combination of zooming primarily with my feet and only using the zoom ring as an additional zoom when required.
I just thought it would be really nice to have a lens that is normally stored (i.e. at its most compact, non-extended length) when at a medium focal length.
AFAIK anything between 35mm to 50mm full-frame-equivalent can be considered “standard” or more or less “neutral” focal length, but to the best of my knowledge you’re right. The precise value for the most neutral (i.e. non-wide-angle and non-zoomed-in) focal length is equal to the image circle’s diameter as measured by the diagonal of the image sensor. For full-frame cameras that would be around 43mm (mathematically, for a sensor that measures precisely 36mm by 24mm, it would be 43.267mm), for APS-C around 28.84mm. A few manufacturers have created 43mm primes. (I’m guessing that you and most others here know this already, but it might be interesting info for some people. Please correct me if I’m wrong on any of this.)
For the purposes of having a “neutral” focal length for the smallest (=storage-ready) point of a zoom lens’ range, imho anything between 35 and 50 would be close enough.
Ah, that’s very interesting, thank you. So lenses like that do exist already, and they’re kit lenses to boot. I wonder why more advanced lenses don’t feature a design like that.
Don’t want to sidetrack the discussion, but can anyone explain why this is significant? Is there some practical consideration for optical design that makes the “neutral” special, compared with primes, say within \pm 20\%?
It’s said to be the most natural angle of view, but more than likely it’s just the mathematical beauty of having a focal length which matches the image circle’s diameter which is attractive to some people (including myself). It’s photographic esoteric.
I’m still googling around trying to find articles (or ideally, studies) which discuss the topic of “normal” focal length. Most of the articles I’ve found so far only or primarily talk about “normal” FL in terms of reproducing human vision as closely as possible, which is obviously impossible to perfectly achieve anyway and additionally makes very limited sense without (primarily!) considering the field of view covered by a picture as a product of reproduction size and assumed average viewing distance (see OT below).
So my primary interest in “normal” FL is in terms of mathematically defining the middle between wide and tele, or rather, with the question of whether clearly defining a normal FL in this sense is even possible.
OT:
As far as field of view / approximating human vision, I’ve long been fascinated by the thought of using a combination of print/display size, assumed viewing distance and corresponding focal length. I’m still mildly obsessed with optical effects like having objects appear exactly life-sized on screens or prints, whether it’s in a photo or in a movie. To me, this has a certain eerie quality that I find fascinating for some reason. Think watching a movie on a big screen and e.g. a human or car in the frame appears to you (at that screen size and at your particular viewing distance) exactly as big as it would in real life.
This could work both in tele (for small prints/displays and greater viewing distance) and wide angle (for large prints and short viewing distance).
My idea (wouldn’t call it a plan yet) would be to eventually take certain planned pictures to hang in certain pre-planned places with deliberate consideration to print size and viewing distance, where approximating the human field of view covered by that print/display size at that viewing distance would correspond to using a certain focal length.
For this reason it still irks me that cameras (of all manufacturers, to the best of my knowledge) don’t display the currently set focal length in the display along with all other infos, even though the FL data is obviously recorded and stored in the RAW file.
Back to the topic at hand: imho Leica is simply trying to cash in on the rather esoteric, abstract aesthetic of having a focal length equal to image circle diameter. Which I would totally buy into if I had that amount of cash just lying around
