Metabones Speed Booster Adapter Makes Your Lenses Faster, Wider and Sharper


If you read the title and thought “huh?” you’re not the only one. Hearing that an adapter can actually make your lenses faster and wider sounds a bit like photography science fiction, but it’s true and it’s getting some serious attention online — it’s Metabones’ new Speed Booster.

If you want to get into the nitty gritty details of how it works you can find the whole white paper here. The TL;DR version, however, goes something like this:

The Speed Booster is what’s called a focal reducer (see diagram below), basically an inverted teleconverter. Where a teleconverter increases magnification, the Speed Booster has a magnification of x0.71. Because of this, more of the image and more light is able to fall onto the sensor


When you attach a full-frame lens to the adapter, it will give your mirrorless’ APS-C or MFT sensor nearly full-frame coverage out of that lens, while increasing the amount of light hitting the sensor by one stop. So a 50mm f/1.4 effectively becomes a 35mm f/1.0.


Because of the way the adapter works you’ll have to use full-frame lenses if you’re using a Sony NEX body. However, Micro Four Thirds speed boosters are also in the works, and those sensors are small enough that you can attach EF-S or DX lenses to the other side.

The Speed Booster will cost you $600, and should be available starting sometime this month. The EF to E-Mount Speed Booster is already up for pre-order; however, speed boosters should releasing shortly for both Canon EF and Nikon FX lenses adapting to both E-Mount and Micro Four Thirds systems.

Thanks for sending in the tip, Troy!

  • Dozen Meda

    Great, the only thing I dont get: Why start with Canon EF and Nikon F? Both mounts are supported with native full frame cameras already. Why not Canon FD, Minolta MD, Konica AR, X-Fujinon (yes, thats Fujis old SLR bayonet mount), Leica M… ???

  • OSAM

    Yeah I’m just gonna go and call shenanigans right now.


    If I’m not mistaken (correct me if I’m wrong someone?) This would be to use a full frame lens (ef mount) on a crop sensor camera (ef-s mount), but to get that full frame coverage ON the crop frame camera, thus, eliminating the crop factor altogether

  • cky

    “It it is too good to be true, chances are that it isn’t true” -Common Sense

  • socool

    I know! A slightly cheaper passive mount would be awesome for old lenses!!!!

  • Rob S

    Yeah……sounds a lot like “Disk Doubler” or “Soft RAM.”

  • D.G. Brown

    It makes APS-C (especially the little mirrorless cameras) slightly better as backup cameras for a fullframe DSLR. It makes my brain hurt switching between FF and crop. The increase in effective aperture also would be nice to make up for the lack of light sensitivity, though that’s apples and oranges. Also might be neat for Brenizer Method pictures (I’d love to try it with my 85mm f/1.2).

  • Jesse

    yes that is right except it won’t ever work on a ef-s mount camera due to flange distance.
    it works with sony e-mount because the mount is closer to the sensor.
    Forget all the math about 501.4 becoming 351.0. Just pretend your using a FF sensor. Your nex-7 no longer applies the crop factor to the lens. it acts as if it was FF with a 501.4.
    all the reverse crop factor numbers is whats confusing people.

  • Jesse

    they exist and lots of people have them already.
    It makes perfect sense, nikon even implemented one in an old digital camera with a 2/3″ sensor. in that case I believe it was adding 4 stops because the sensor was so small.
    Vantage also currently offers something very similar and have for sometime, although its expensive and is for PL tele lenses.

  • Jesse

    Leica won’t work because it already has a very short flange distance. They chose EF because lots of people have EF lenses. And lots of those people also have sony mirrorless cameras where they want to use them.

  • 11

    correct me here?
    If you look at it, it is concentrating light that was spread over a larger area (FF Sensor) to a smaller area (APSC Sensor). So, the apparent f# has increased because the same light is focused on smaller area. But at the same time, the light available to pixel photo-cite is the same. If both FF and APSC are of same pixels, they both should get same light/pixel … ???

  • Rui Nelson Magalhães Carneiro

    Because you can use Nikon-to-Canon adapter and other adapters to Canon mount with it. It’s like having a Full Frame canon DSLR converter to NEX

  • Rui Nelson Magalhães Carneiro

    No, because the flux is the same, but the area will be smaller.

  • Luiz Fellipe Carneiro

    Another glass between lens and sensor, another chromatic aberrations, distortions, and so.

  • Alex Szecsi

    APRIL FOOL !!!!!

  • G

    You’re taking light that would have been spread over a larger sensor (or “wasted” with a crop sensor) and concentrate it onto a smaller sensor => higher light density = faster lens (dunno how it will affect dof and IQ though).

  • 11

    what about per-pixel flux? because the pixel area has reduced too…

  • Bartek Nowakowski

    This is similar to focal reducers for telescopes. My 600mm f7.5 ED telescope turns into a 510mm f6.3 scope with a x0.85 focal reducer attachment. The idea has been around for a long time.

  • wickerprints

    A wide-angle converter is basically a condensing group of elements. Because it shortens focal length as well as decreasing f-number, the depth of field does not change. It is literally the opposite of a teleconverter.

    The lens that Zeiss designed for Stanley Kubrick for his film “Barry Lyndon” was essentially a fast prime lens with a wide-angle converter in the rear. The lens nearly touched the film plane; that is to say, the back focal distance was extremely short–a necessity to achieve fast f-numbers. This is why such an adapter cannot be used to increase the light-gathering ability of a lens on an SLR body, because the mirror box prevents the attainment of this distance, whereas it is possible for mirrorless bodies such as the Sony NEX and Micro 4/3rds.

    Do note that the actual realized t-number won’t be improved by a full stop, for two reasons: the presence of additional optical elements loses a little bit of light, and the oblique angle at which marginal rays strike the sensor means some of it fails to reach the photosite. Combined, I would hypothesize that these would lead to light losses of around 1/4 stop, so the net gain would be something like 3/4 stop.

  • E

    I think they realise that the real money is in lenses that are still widely used rather than what is relatively obscure lenses today. If they want to get this thing flying, focusing on Canon EF and Nikon F makes sense for now.

  • DF

    Would you say your lens becomes slower if you increase pixel count on a sensor? Smaller pixels means potentially worse signal to noise ratio.

  • DF

    If the rear element is so close to the sensor I guess you might have issues with vignetting and colour cast towards the corners also.

  • Jayy

    Still sounds like SciFi for photography after reading it twice…

  • Jayy

    Never mind. The white pages have enlightened me

  • Zach Sutton Photography


  • Bas

    Sounds logical. One question though – since the physical aperture size stays the same and focal length is reduced by bending light (more than it would without the adapter), would this have any effect on DOF? I understand that light concentration would be greater resulting in faster lenses, but is the mentioned f-stop an equivalent rather than a “real” f-stop including all of its properties (such as DOF)?

  • nab111

    When I read the title I thought “oh, what a load of cr*p!”
    After reading the first few paragraphs I thought “ahh, this is actually quite a neat idea!”
    I then read the price and thought “$600!?!? No thanks, I would rather just put that towards the price of a full frame camera”

  • 9inchnail

    It’s called physics. You might wanna read a book from time to time.

  • 11

    yes, I see what you mean. Thank you!

  • 11

    The lens used for the candle light shot of movie Barry Lyndon used a 50mm f/0.7… which had a 4mm or so flange distance. I now see how this could be possible.

  • 11

    I was wondering about that carl zeiss Stanley kubrick lens. Now it makes sense. I always thought they did some rocket science magic to get f/0.7 … as I remember from some documentaries, the flange distnace was around 4mm..

    It would be nice to see the math of mamiya 80mm f/1.9 lens (4×6) converted to an EF full frame, mirror-less to see to how much of a f/# gain that gives…

  • neoBIT

    He-he… So a 50mm f/0.95 effectively becomes a f/0.67 *ROFL*

  • neoBIT

    50mm x 1.5 (crop) x 0.71 (magnification) = 53.25mm

    F/1.4 x 1.5 x 0.71 = 1.491

  • 9inchnail

    Why would it make a lens sharper?

  • Joshua Morin

    Will it work on a Nikon APS-C camera like the D7000?

  • palmbook

    I think DOF will stay the same, as on FF camera. Just imagine you have an image projected on the area of FF sensor. Then, you squeeze it into the size of APS. What you would get is essentially – Higher light intensity (becos you project the same amount of light onto a smaller surface) – Higher sharpness (same reason) – Same DOF as on FF sensor (becos the bokeh would get resized proportionally to the size of APS)

  • Stan

    A 35mm f/0.67, yes. Good luck focusing that.

  • Stan

    Except Kubrick used one.

  • Sporkguy

    Sharper on a smaller sensor compared to without the adapter because, as many people above me have typed, you’re getting more glass into the same area of sensor. Imagine if you will a higher resolution of light landing on the sensor.

  • Antonio Carrasco

    yes, it is actually a very useful device if it functions as advertised, but the price is very, very high

  • Antonio Carrasco

    there is no focal length magnification factor on max aperture

  • Jesse

    No it won’t.
    Essentially it will work and can be made for lenses that are intended for cameras with mirrors, on cameras without mirrors.

  • Joshua Morin

    Is that because of the flange distance?

  • Jesse


  • Joshua Morin

    Stupid flange!

  • Angela Henderson

    Yeah. That’s more than the cost of the lens I was hoping to improve.

  • Roy

    It’s called physics. You might wanna read a book from time to time.


  • Teq

    Would like to see this applied to medium format lenses on full frame cameras :P

  • Guest

    It will behave like a 50 0.95 as far as focusing is concerned (and a 35 0.67 wouldn’t have a shallower DOF).

  • Martin M

    How can everybody be so sure it can’t be done for SLRs? What is the problem with the flange and why couldn’t that obstacle be overcome?