11

I really like prime lenses for their simplicity, zooming with my feet. I prefer it to a zoom lens because of this simplicity.

But I do carry both a 35mm and 50mm because I do two different things with them, e.g. street and portraits. I would prefer to have one lens that is 35mm and 50mm which can be toggled.

Is it technically possible to make a toggle lens? How would you do it?

  • 1
    If you do not want to change lenses you can carry two cameras. – Carsten S Dec 25 '16 at 20:36
  • Canon recently patented a lens with two teleconverters "build in". – agtoever Dec 26 '16 at 7:19
11

Yes it is technically possible. The question is whether this will have practically same limitations as a zoom or not.

There are two objectives from Leica with stepped focal length adjustment: the 16-18-21mm Tri-Elmar and Tri-Elmar 28-35-50 and a Canon zoom objective with built-in teleconverter which would do what you want if placed inside a fixed focal length objective: EF 200-400mm with Internal 1.4x Extender .

  • Wow the Tri-Elmar 28-35-50 looks very interesting. If it was smaller, lighter and more performant, like f2 at 50mm, it would seem like the perfect lens for a lot of people. – Igor Nadj Dec 29 '16 at 5:13
  • @igor there is basically the same issue with it as with fast zoom: look, from all vendors which could benefit from it only Sigma made a 24-35/2 and it is huge. I guess that Leica could make it smaller but it still shows how troubling fast zooms are. – Euri Pinhollow Jan 13 '17 at 16:13
  • yeah I see that now, the extra bulk is unavoidable – Igor Nadj Jan 17 '17 at 3:17
22

Yes, it is possible and a "Lens Turret" is one way of accomplishing it.

It was very common to use a "Lens Turret" on film and movie cameras in the 1950's before zoom lenses became practical.

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Source: Bolex 16mm

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Source: Macro lens turret

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Source: 8mm film camera with lens turret

  • 5
    That A900 looks...eldritch. O.o – skytreader Dec 24 '16 at 17:36
9

It is possible and Canon has done it, although in a different way than you'd expect - their EF 200-400mm f/4L IS USM Extender 1.4x. It's a zoom lens with a built-in teleconverter that could be toggled (instead of unmounting the lens and mounting it again with a teleconverter like you would normally do). This, however, reduces the amount of light you have when you're using the teleconverter - you only get to f/4 when not using it; it drops down to f/5.6 with it.

Although it seems theoretically possible to do the same with a short prime (35 or 50 by your example), it would not be practical - the teleconverter part itself would weigh as much as a prime lens by itself.

In recent years some fast zoom lenses appeared that are as good as or better than equivalent primes - notably the Sigma 18-35 f/1.8, the 24-35 f/2 and the 50-100 f/1.8. Weight, however, is still an issue - even the lightest of the three (the 18-35) weighs 800 g.

  • It's not just Sigma. Canon has the EF 24-70mm f/2.5 II, EF 70-200mm f/2.8 L IS II, and EF 11-24mm f/4. The first two are as good as all but the very best of their prime lenses in the same focal lengths. The 11-24 is better than any prime Canon sells wider than 24mm. Nikon has started to up their game with their top end zooms as well. – Michael C Dec 24 '16 at 21:55
  • I was writing under the assumption that we're talking about fast primes - the general reason that people would buy a 50 f/1.8 over a similarly priced zoom. It's just that Sigma was the first (and still the only one to my knowledge) to introduce a f/1.8 zoom. Will edit my post to reflect that. – K. Minkov Dec 25 '16 at 12:43
  • Gotcha'. Yeah, the only problem with that is that pretty much all of those lenses are APS-C only aren't they? So to use them you give up the 1-2 stop low light advantage of a larger FF sensor and you're right back to the performance of FF + f/2.8. – Michael C Dec 25 '16 at 15:44
5

Yes, it's possible, and technically there are a number of different ways this is achieved.

You can have a lens turret that contains multiple lenses with different focal lengths, where you rotate the turret to switch between the desired lenses—this was commonly used on movie cameras.

You can build a "stepped" zoom lens--i.e., have a lens that changes focal length, but not continuously through a range, only to pre-specified distances for which the lens is optimized (e.g., the Tri-Elmar lenses by Leica).

Or you can use a teleconverter on the back of the lens, e.g., as an add-on like the Canon Extender EF 1.4x, or an internal element that swings up into place with the flip of a switch (e.g., the Canon 200-400L—the bulge in the barrel is where the TC element lives).

Or you can use a teleside converter on the front of the lens, e.g., the Fuji TCL-X100 that converts an X1000-series camera's 35mm-equivalent lens to make it a 50mm equivalent. For the usage scenario you're describing, this is possibly the closest match that actually exists. :) But, of course, is pretty much the same as just using two separate lenses.

0

It is technically achievable, outside eldritch lens turrets, with constant (not fixed) aperture zoom lenses.

The technical reason you'd go for a prime over a zoom is because it is easier to achieve wide apertures with primes (hence primes are often the "fast" lenses). The maximum aperture achievable with your typical zoom lens (like a kit lens) decreases as you zoom in.

But constant aperture zoom lenses allow you to zoom without penalizing the maximum aperture. For instance, the SAL1650 2.8 can do f/2.8 at 16mm up to 50mm. The effect of which feels like I have a f/2.8 prime from focal lengths 16mm to 50mm, toggle-able with the twist of a lens barrel.

I haven't seen much constant aperture zooms around but the SAL1650 does not feel as "simple" as primes. But I think it is definitely simpler and more manageable than lens turrets.

  • One might also go for a prime over a zoom for the relatively low cost flat field performance you can get with a consumer macro lens like a 90mm or 100mm f/2.8. Primes are very often about wider apertures, but not always. – Michael C Dec 25 '16 at 15:49

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