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, 2016 at 20:36
  • Canon recently patented a lens with two teleconverters "build in".
    – agtoever
    Dec 26, 2016 at 7:19

5 Answers 5


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, 2016 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. Jan 13, 2017 at 16:13
  • yeah I see that now, the extra bulk is unavoidable
    – Igor Nadj
    Jan 17, 2017 at 3:17

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, 2016 at 17:36

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, 2016 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, 2016 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, 2016 at 15:44

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.


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, 2016 at 15:49

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