on landscape The online magazine for landscape photographers

Novel Adapter for NEX


mb_spef-e_03sOne of the problems with using full frame lenses on a cropped sensors is that your focal length is 'increased' by the same amount so if you use a 'normal' 50mm lens on a 1.6x crop sensor it becomes a medium telephoto of about 80mm.

Not only that but the amount of light is also reduced so that the effective aperture becomes increased also. This means your f/1.8 normal lens has the same light gathering ability as an f/2.8 lens and also the same relative depth of field.

However, Metabones have created a focal length reducing adapter for the NEX that allows you to mount Canon EF mount lenses on Sony E mount. Only for Sony crop sensors though.

Effectively what is happening is it's bending the light from the limit of the image circle of the lens so that it properly covers a crop sensor rather than a full frame sensor. It's like an EF to EF-S converter!

Now Philip Bloom has been testing the adapter and seems to like it a lot (see Sony Alpha rumours website too) but obviously he's only testing it in terms of HD resolution which is less than half of the resolution of the camera as used for stills. It remains to be seen whether the optics in the adapter are good enough to be used whilst retaining the optical performance of the original lens.

What it does do is allow you to use tilt shift lenses on a Sony NEX camera at the original wide angle focal lengths! Very interesting!!

We'll try to get more information from the supplier about how good the performance is but Prof. Brian Caldwell who supplies the optical elements for the adapter has a very good reputation in lens design for scientific and archival purposes.

The lens is on pre-order at the moment and the price is a quite hefty £380 but it's a definite sign of what the NEX and it's short distance from sensor to lens mount allows custom manufacturers to do. Interesting times...

UPDATE: Here's a quote from Brian Caldwell

"We designed an entirely separate optical system for micro 4/3. However, the magnification is the same as the NEX version: 0.7x. In order to get a significantly smaller magnification while maintaining excellent image quality we would have had to get much closer to the image plane with our optics. Unfortunately, the m4/3 cameras don't allow this.

The good news is that the performance of our 0.7x optics for micro 4/3 is really good, and I expect that some pixel peepers will prefer it over the NEX version. If you look at the MTF curves in the white paper you can see that the m4/3 version gives higher performance in the corners than the NEX version. We could have saved a lot of money by re-using the NEX optical cell for the upcoming m4/3 Speed Booster, but we decided to maximize image quality instead."

Which m4/3 camera do I buy?

  • If it doesn’t degrade the image quality this is going to be a ‘break through’ product. Being able to use the Canon tilt shift lenses would be a big plus to the NEX system.

    The idea of using focal length reducers is apparently not new….

    “Barry Green over on dvxuser mentions that “the Olympus 14-35 & 35-100 f2.0 zooms are just 24-70 & 70-200 lenses redesigned with focal length reducers”.

    But these are integrated into the lens and custom made for each zoom. Although this is just speculation, as this has not been confirmed by Olympus.”

  • danfascia

    Using alternative mount lenses is pretty much the key to these compact systems for me. Mounting my Zeiss and Leica glass on the Panasonic GX1 has been a revelation, although the 2x crop factor limits this for wide landscape purposes. For documentary and portrait work, it’s a killer combo.

    The NEX system doesn’t suffer quite as badly from the crop issue of course. Worth watching!

  • AlexeyD

    > Not only that but the amount of light is also reduced so that the
    > effective aperture becomes increased also. This means your f/1.8 normal
    > lens has the same light gathering ability as an f/2.8 lens and also
    > the same relative depth of field.

    That is not quite correct though. The f/1.8 on 50mm lens means that max lens aperture is 27.8mm and that stays the same no matter what sensor camera it is mounted on. The amount of light reaching sensor does not change. A more correct way of thinking of that would be that if on crop sensor an equivalent angle of view is required then 33mm (for a crop factor of 1.5) would be needed. For the 33mm lens to admit the same amount of light as 50mm f/1.8 on a full frame, the same size of opening/aperture of 27.8mm (therefore admitting the same amount of light) would require f/1.2 lens (1.8 divided by crop factor). If we are talking about using the same lens at the same apertures on different sensors, DOF does not change either.

    • Hi Alexy, hopefully my ‘caveat’ the ‘”effective” aperture’ makes it clear that it isn’t actually changing the aperture – just having the same effect as. The total amount of light hitting the crop sensor is less than that which would have hit the full frame sensor with the same lens.

      Agreed that to get the equivalent lens you need a wider focal length and faster lens by the ratio of crop of full frame.

      Your last comment that the same lens with the same aperture on different size sensors isn’t quite correct. The blur circle stays the same but because we have to enlarge the sensor image more to get the same print size, any blur is increased in the final picture.

      Perhaps this needs an article of it’s own – do you want to chat offline about it as I only *think* I’m right ;-) ?

      • AlexeyD

        Yes the DOF point is arguable and if looked from enlargement prospective then you are correct.

        >The total amount of light hitting the crop sensor is
        > less than that which would have hit the full frame
        > sensor with the same lens.

        This however I don’t agree with (at least as it stated). Consider the image plane inside lens projected image circle, ignoring light fall off towards the edge of the projected image circle, amount of light delivered to a unit of the projection plane (say a square inch) is the same. This is regardles of whether that square inch is part of cropped sensor or FF sensor placed at that projection plane.

        • The usual measure of ‘amount of light’ is light delivered over the surface area. e.g. if you have a big window you would have more light but if you had a small window then you’d have less light regardless that the suns delivery is the same per square mm.

          • AlexeyD

            The window in this case is the same – say for 50 mm f/1.8 lens its 27.8mm regardless of the sensor size underneath this window.

            • I was talking about light hitting the sensor though – not light coming through the lens..

              • AlexeyD

                True the cropped sensor will receive less light overall surface because of the smaller area but the same area of bigger sensor will receive the exactly the same amount of light. Even more, each pixel will receive exactly the same amount.

              • AlexeyD

                I think I understand your position now will try to recap it here so let me know if I am wrong. You consider just the amount of light delivered at the overall area to cropped sensor in comparison to larger area of FF sensor detached from any other factors – is that correct?

                This is imho not entirely correct starting point and leads to “confusing” statements about lens aperture and speed. The exposure itself does not change regardless of the size of projected are – smaller sensor can be considered just a crop of the larger one (say like crop mode in FF cameras) with all other parameters being the same. It does not change the lens focal distance, aperture or anything else for that matter. This is of course if we consider the lens alone isolated from all other factors (and this is usually a perception of generic statements like this about cropped sensors).

                However if we are considering this all from the prospective of the scene being recorded, i.e. the same scene recoded on both cropped and FF sensors (meaning exact framing of the image is the same in both cases), then we can talk about equivalent amount of light delivered (because it has to be the same for the same capture). In this case my first post here holds – the lens focal length needs to be adjusted to match the angle/framing (assuming we are shooting from the same position) and that causes the aperture change (as it is relative to focal length). Which in turn will mean that in this particular case you are right and to get the equivalent exposure/amount of light to cropped sensor it will need a larger/faster aperture.

                If however we leave the lens exactly the same and simply move the cropped sensor camera closer to the subject achieve the same framing as FF camera with the same lens, then nothing really changes exposure wise or light delivered to the sensor – it will be exactly the same. The only thing that changes in this case is DOF.

  • I have read through most of this and side with AlexeyD.

    The depth of field is the range of distances either side of the distance focused on where the cone of light through a lens from each point in the object will appear as a point even though it is a circle, because the circles are too small for the eye to differentiate from a point. That is called the circle of confusion and, because with a smaller frame size one has to magnify the image more for a standard print size, hence the depth of field will be less for a given focal length and aperture than on a larger frame size.

    In photography, a given aperture is a measure of the light intensity. That is all we are interested in because we have to adjust the exposure time to correspond with that. The total amount of light hitting the sensor or film is not a concept of any use or relevance in photography just as how many miles per gallon my car will go per square centimetre of petrol in my petrol tank (at the liquid surface or anywhere else given that the tank is an irregular shape) is of no interest whereas the mpg is everything.

    Tim. I think you got yourself into a corner over that one and politely suggest you should have owned up.

    The Metabones for the Micro Four Thirds is very much of interest to me even though it is expensive as I just bought the Olympus E-PL3 new for a mere £190. I want the equivalent of 12-24mm on my Nikon D300 which I have with my super Sigma super wide angle which is as good as distortion free on full frame at all focal lengths as well as on DX and I use it 95% of the time since street scenes and landscapes are all that is of interest to me on a regular basis. The Olympus 90-18mm lens just is not good enough and the Panasonic 7-14mm is far more expensive than I am prepared to countenance. If the Metabones really is nearly as good to the edges as at the centre coupled with my 14-42mm kit lens with the Olympus 4/3 body then a long trek into the mountains will become a pleasure instead of the discomfort I experience with the bulk and weight with my Nikon D300 even without my two other lenses, love it other than in those circumstances though I do.

    And, by the way, as far as I am concerned, either is good enough for an A2 print of a good picture with 12mp on either camera. IMO the increase in megapixels with more recent cameras is mostly a marketing ploy by camera manufacturers and not really needed by most photographers.

    • Hi Stephen – I’m not sure I get your point. The aperture is not a measure of light intensity at all, it’s the ratio of the focal length of a lens to the effective size of the aperture (the entrance pupil). The amount of light captured by a lens is proportional to the area of the aperture but the proportionality isn’t constant for various lenses.

      In fact two lenses with the same f/number and same focal length can have different exposures on the sensor. If you want a measure of light value for a sensor you need to use T stops. This is calculated by measuring the amount of light hitting the sensor, and why you get a ‘bellows factor’ affect if you focus closer than infinity because when you focus closer you move the sensor away from the lens and hence the light diverges more and the total amount of light hitting the sensor is reduced – hence why “total amount of light” is useful.

      You comparison of circle of confusion is quite right – however if you want the same field of view and perspective (which surely you need if you’re going to compare cameras) then you need to use a longer lens if you’re going to use a larger format/sensor.

      At the end of the day I did the calculations for depth of field relating to aperture and focal length and wrote an article about it.


      You can use the calculator I wrote at the bottom of the article to compare things. As an example if you use a four thirds sensor and want the same depth of field as a full frame at f/22 you can use f/11 on the four-thirds.

      At the bottom line, small formats give you a LOT more depth of field – hence why people want larger formats when they want less depth of field.

      Just spotted the extra bit – is the 14-42 lens an EF? It sounds like a cropped format lens? The metabones converts full frame lenses to smaller format ones – I’m not sure you’ll get full coverage if you use a crop lens.

      p.s. print quality is a subjective thing and one persons adequate A2 print is not anothers – an A2 from a D300 is about 150dpi given anti-alias filters etc. Perfectly adequate for most uses but a 300dpi image will look significantly better. Better enough to matter? That’s down to the artist. Dav Thomas has an iPhone picture in his latest book so why does he bother owning a Sony A900 (never mind large format!)?

  • I have no idea what went wrong but my previous entry appears to be included twice but the correction first time around got lost even though I posted it before Tim had time to read it and reply (unless he read what I wrote before I had posted what he was replying to !!!!).

    Tim, We will have to agree to disagree.

    I believe you are the only photographer I ever have heard refer to the “total amount of light” or think it is useful in sixty years! Of course if you were designing light meters which measure the average or another computation over the whole frame like many do, you’d have a point. I use spot metering on my cameras and choose a mid-tone to base all my exposures on, in effect the Ansel Adams zone system in spite of automation in modern equipment which I personally do not like or use. Likewise, I have disabled autofocus from the shutter button on my D300 as I always prefocus where I choose. Of course for action photography, either measure would be rather stupid.

    You are right that the f stop is the measure you stated but it also is a measure of the light intensity given that the step in the aperture scale uses sqrt 2 as the increment as any photographer should know. You are correct about T stops. of course but in most cases the absorption and reflection is small enough to ignore and so is the bellows effect until you get very close.

    I do agree that smaller formats give you a lot more depth of field but that is because you need a shorter focal length for the same angle. The same focal length on a smaller format gives less than on an larger format because of the higher magnification but even so you are still ahead. For example, with 18mm on APSC (Nikon DX) you will get more DOF than 27mm on full frame at the same aperture and the angle on each will be the same.

    Incidentally, while I do agree about needing a larger focal length lens on a bigger format, that is principally to get the same angle coverage as with the smaller format. A lens may distort because of curvilinear distortion but it does not alter perspective. That is a very common misconception. From a given position any lens will give the same perspective because perspective is a function of that position relative to what is in the field of view, nothing else.

    I am now retired but I used to work in IT, so we also have that in common. Also being very mathematical I liked to prove formulae from first principles for DOF and other things from my youth just for the hell of it. But that was a long time ago.

    I also have to add this about the , Metabones. I realised that for me it will be useless. Has I been able to use it on 4/3 with a 4/3 lens it would have been great but the bulk and weight with a Nikon lens on 4/3 is unsustainable. Why on earth they do not make the device for a given lens to scale down by 0.7 on the same camera as originally designed for quite escapes me!

    • No problem disagreeing but I’m a bit clueless about what we’re disagreeing about now.

      As for scaling a lens focal length by 0.7, it’s impossible without changing the coverage of the lens – hence you need to have a larger image circle to begin with.

      As for bellows factor – it may be insignificant for four thirds cameras as you have to be very close but for large format it becomes a factor quite often.

      p.s. total amount of light can also be called ‘candela’ so the total amount of light coming through a lens can be given in candela. The total amount of light hitting the film can also be expressed in candela. The exposure is based on candles per square meter or foot. Personally I think candles are pretty useful even if I refer to them as ‘total amount of light’ to avoid confusion for people who don’t know what a candle is.

On Landscape is part of Landscape Media Limited , a company registered in England and Wales . Registered Number: 07120795. Registered Office: 1, Clarke Hall Farm, Aberford Road, WF1 4AL