Metabones Nikon F to Fuji X adapters – part II

The Speed Booster: it’s a kind of magic!

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When Metabones originally announced the concept of its Speed Booster, in January 2013, the initial reactions ranged from rather skeptical to overly enthusiastic. Indeed, the claims for this product are all that is need to start us dreaming: a focal length multiplier of 0.71x (nearly eliminating the field-of-view reduction by APS-C crop sensors), a maximum aperture increase by 1 stop, and the promise of increased sharpness and reduced optical aberrations. Sounds too good to be true, isn’t it?

Yet, all I can say after five weeks of exploration and testing is that so far the Speed Booster has lived up to all my expectations – at least from the optical side. More about that later, when we look at detailed test results.

So what is the Speed Booster?

The Speed Booster is a focal length reducer, something you can think of as the reverse of the well-known 1.4x teleconverter commonly used with long lenses. Such a converter enlarges the image projected by the lens so that it covers a larger area than the film or sensor can capture: the result is a ‘cropped’ image and the reduced field-of-view (FOV) makes the focal length of the lens seem longer. At the same time the incoming light is spread over a larger area, so the amount of light captured by the film or sensor is lower: the effective aperture is reduced. Typically, a 1.4x converter will come with a 1 stop loss of light.

The Speed Booster too inserts between a lens and a camera body, but its optical elements create the opposite effect: the light from the lens is compressed onto a smaller imaging circle, better adapted to the crop sensor. As a result, the field-of-view is enlarged (countering the effect of the sensor crop factor) and the amount of light illuminating the sensor is increased (resulting in a larger effective aperture). Obviously, this can only work combining a full-frame lens (having a large enough imaging circle to start) with a crop sensor not exceeding the size of the reduced imaging circle.

 

Here we see a full-frame lens mounted on a CSC with an APS-C sensor, via a ‘straight’ adapter. The required focal flange distance is restored. The lens still projects a full-frame image circle, of which the sensor captures only a cropped area.

 

The Speed Booster optics reduces the image circle to more closely cover the APS-C sensor, resulting in a field-of-view that matches the full-frame behavior of the lens. All available light now hits the sensor.

 

Here’s another way of looking at what’s happening:

At left, the unmodified imaging circle of a full-frame lens: it adequately covers the full-frame sensor area (green rectangle). The Fuji X-cameras with their APS-C sensors capture only a reduced crop area (red rectangle). At right, the situation with a Speed Booster: the original imaging circle is reduced, and no longer covers the full-frame area. Instead, our crop sensor now captures the scene with a field-of-view close to the full-frame rectangle at left. In addition, the image gets brighter as all available light is concentrated on the smaller imaging circle.

The next two images (shot in my improvised table-top product studio) illustrate the difference in field-of-view. On top in the first image, the scene captured with a ‘regular’ lens adapter; at the bottom the same scene shot from the same position, this time using a Speed Booster. Also note the change in exposure time: the 1-stop gain in effective aperture is real!

The second image shows exactly the same top half part, but when using the Speed Booster the camera was moved in closer to obtain more or less the same size for the main subject. The change in vantage point explains the difference in perspective, causing more of the background to be visible.

(Note that the darker corners are partly caused by the lighting on my makeshift test setup)

Optical design and specifications

The concept of a focal length reducer is not new: the approach is for example commonly used in telescope eyepieces. Some specialized lenses have focal reducers integrated into their optical design. A practical general purpose add-on focal reducer for photographic applications was never realized: one of the bottlenecks was the difficulty to create room for additional lens elements while maintaining the required focal flange distance. It is the difference in register distances between a full-frame (D)SLR lens and a CSC body that created the opportunity to build a Speed Booster.

The Speed Booster is designed by Brian Caldwell, a highly respected optical engineer, and Wilfried Bittner, a specialist in opto-mechanics. Both veterans have worked together on numerous product development projects. They jointly filed a US Patent Application (ref. 2013/0064532A1, should you want to read it) and Caldwell’s name proudly figures on the adapter’s barrel, next to a real serial number (as any precision optical device deserves).

The two inventors have published a white paper on the Metabones website with details and background on the design. You better have a minimal understanding of optical principles and basic lens design to appreciate it, but if you do the comprehensive document is very convincing. And if you rather have a second opinion from another independent qualified expert, I can recommend the initial test report published by LensRentals’ Roger Cicala.

Metabones currently offers two Speed Booster designs: one for APS-C sensors with either Sony NEX or Fuji X mount, and a slightly different one for Micro-Four Thirds.

These are the specifications for the Nikon-F-to-Fuji X version:

• 4 lens elements in 4 groups
• Magnification: 0.71x
• Maximum ‘input’ aperture: f/1.26
• Maximum ‘output’ aperture: f/0.90
• Focal flange distance reduction: 4.16mm

At this moment, there are also Fuji X-mount compatible Speed Booster variants accepting Alpa, Contarex, Contax Yashica and Leica R lenses.

The presence of additional optical elements causes a slight reduction of the flange focal distance for the lens+adapter combination. The Speed Booster therefore is some 4mm shorter than both the F-adapter and G-adapter.

Lens compatibility

The Nikon-F-to-Fuji X Speed Booster will accept almost any full-frame (FX) Nikon or F-mount lens, including pre-AI, AI, AI-S, AI(-S) modified, AF, AF-D and AF-S models. G-type lenses are supported as this adapter comes with its own unique aperture control ring.

The ‘native’ imaging circle for all these lenses covers the 43.3mm diagonal of the full 35mm frame. After the 0.71x size reduction, the resulting 30.7mm circle more than covers the ca. 28mm diagonal of the APS-C sensor.

DX lenses cannot be used, as in general their reduced imaging circle will fall short of the APS-C sensor requirements and cause heavy vignetting.

The Metabones website lists two older Nikon lenses as mechanically incompatible. In the case of the AI-S 20mm f/2.8, the reason is a plastic shroud surrounding the rear element that extends some distance and would hit the front element of the Speed Booster (in this specific case, it’s possible to remove the interfering part and keep a working lens).

Product claims

Let’s summarize the list of features and benefits that the Speed Booster should (and actually does) deliver:

• The effective focal length of the lens is reduced 0.71x. That means that the field-of-view is now 1.4x wider. Together with the 1.5x crop factor from the APS-C center, the final field-of-view becomes 1.5x0.71=1.065 times what you get with the same lens on a full frame camera: almost the same in practice;
• The effective maximum aperture is extended by one full stop: you can now use faster shutter speeds, lower ISO settings (and less noise), shoot with shallower depth-of-field or in darker environments;
• All aberrations of the mounted lens are reduced in the image compression process; combined with the small aberrations introduced by the adapter optics the final outcome should be an increased optical performance (as indicated by MTF curves) in the center of the image, and a no worse than original performance near the outer edges.
• And what happens to the depth-of-field (DOF)? The short and practical answer to this complex question is that a lens used with a Speed Booster on an APS-C crop camera essentially gives the same depth-of-field effect as if used on a full-frame camera body. That means a shallower DOF than obtained without the Speed Booster.

It takes an excellent test setup and a lot of expertise to verify these claims by the numbers, something that is well beyond the means and skills of a ‘normal’ photographer. All measurements executed and documented by Caldwell and Cicala indicate that the claims are not idle at all.

So what do we get out of this?

A number of my prime lenses take on a totally new personality when used with the Speed Booster:

• The AF 50mm f/1.8 becomes a compact 36mm f/1.3;
• My AF-D 50mm f/1.4 turns into a 36mm f/1.0!
• An AF-D 85mm f/1.8 becomes a sharp 60mm f/1.3 lens, great for portraits;
• My old Tokina 17mm f/3.5 now works as a 12mm f/2.5;
• My even older Vivitar Series 1 135mm f/2.3 now serves as a 96mm f/1.6;
• The AF-D 180mm f/2.8 lives on as a 128mm f/2.0;

and so on…

NEXT: controlling the aperture with Speed Booster

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Metabones Nikon F to Fuji X adapters – part I

The look, the feel, the features and the price

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The above trio of Metabones lens adapters are the latest additions to my varied set of 9 ways for coupling a Nikon F-mount lens to a Fuji X-Pro1 and X-E1 camera. It started with the ‘regular’ F-to-X adapter (shown left) as I very much liked the idea of its compact tripod mount. Then, the remarkable Speed Booster (at right) was announced: it incorporates optical components reducing the focal length of the attached lens by 0.71x, and increasing its maximum aperture by one full stop. Obviously, I could not resist finding out for myself whether or not this optical marvel lives up to such bold claims. And finally, just two weeks ago, Metabones announced another purely mechanical G-to-X adapter (the middle one) equipped with the same aperture control ring as the Speed Booster, thus making it fit for use with lenses that have no aperture ring (like all AF-S and DX models).

About Metabones

Metabones is a supplier of high-quality camera adapters and related camera accessories, with a design team based in Japan and Hong Kong, and its own production line in China. All of its products are available directly from the company’s web store (operating out of Hong Kong as Global Boom International Limited), and through selected resellers internationally.

Metabones currently makes lens adapters for use with Fuji X, Sony NEX and various Micro Four Thirds (MFT) cameras, and to a lesser extent for Leica M and S systems. Supported lens mounts include Nikon F, Canon EF, Leica M and R, Alpa, Contarex, Contax G and Contax Yashica. Not all combinations of course all available (or even technically possible).

DISCLAIMER: I do not have any business or other relationship with Metabones. I have purchased each of my lens adapters for my own purposes as a ‘regular’ customer at full price.

Product distribution and pricing

In or around Belgium (where I live) the availability of distribution of Metabones products from retail channels is very rare to non-existent. A few AV/video specialists carry (or at least list) some models in Sony NEX or Micro Four Thirds (MFT) mounts only – which makes sense from a video perspective. No trace whatsoever of Fuji X-mount versions…

I therefore ordered my products on-line from the Metabones site, and had them shipped from Hong Kong by FedEx International Economy. Each time I have been very pleased with the quality of service and speed of delivery (5-8 working days). Obviously, you should expect the usual VAT, import duties and other ‘administrative fees’ added to your bill. I also threw a few follow-up questions by e-mail to Metabones’ after-sales support team, and received prompt answers (though not always the exact information I was looking for).

The Metabones adapters are more expensive than the comparable models from Kipon, but the full cost of the G-version is comparable to its less-featured Novoflex counterpart. The Speed Booster, of course, is quite expensive due to its comprehensive optics (and, no doubt, by its small-lot production setup and its unique position in the market).

These are the current list prices and my final costs:

Packaging and physical characteristics

Approximate dimensions and weight:

Metabones clearly believes that more expensive products require bigger boxes. In the case of the Speed Booster, that results in a lot of foam rubber inside (the other two boxes have no padding). None of the products have user instructions or any other documentation included in the box.

The Speed Booster comes with a few accessories:

• A plastic front (F-mount) and back (X-mount) cap, very useful to protect the optical elements that –especially at the back – come very close to the end of the bayonet;
• A larger allen hex key to remove the tripod foot, and two small plastic caps to seal the resulting screw holes (we will come back to these later);
• A smaller allen key fitting the screws on the front and back bayonet rings.

I am not aware of any (good) reason why a customer would want to remove the bayonet rings, and my inquiry at after-sales support did not provide an answer either (just a confirmation that this was the intention for supplying the smaller key).

As for front and read caps, an eBay reseller happily provided me for just a couple of euros with a dozen each of Nikon-style body caps and Fuji X rear lens caps, so all my adapters are now nicely protected against dust and other FOD when floating in my camera bag.

The Metabones lens adapters are beautifully executed. The aluminum barrel has a black satin surface finish with engraved white markings. Both camera-side and lens-side mounts are precision-machined brass with chromium plating. The front side mount features a leaf-spring structure to ensure proper alignment and tightening of the lens. The inside of the barrels got a rough matte-black treatment, to minimize internal reflections.

The adapters snap easily onto the camera, just like any other X-mount lens. There is no significant play here, just the familiar little wiggle that is equally there with native XF-lenses (and a bit more so on my X-E1 compared to my X-Pro1). At the lens side, all three of my copies initially felt rather (and almost too) tight; they loosened up after a little bit after usage, however without starting to feel less ‘solid’. The lens release lever is nicely done, and the unlocking mechanism works fine. In summary: I am very comfortable with the mechanical fit and operation of these adapters.

All three adapters come with a tripod mount for use with Arca-Swiss compatible quick release clamps, and also offer the classic ¼ inch thread. The Arca plate matches perfectly with the ball head on my light but sturdy Benro carbon travel tripod. The foot extends some 9mm below the base of an attached X-Pro1 or X-E1. That is not very much, and I guess there might be a risk for obstruction if a tripod head has a larger top plate. With the original Fuji hand grip mounted on either camera model, the bottoms of the grip and of the adapter foot end up about flush.

The mounting foot is absolutely great when working with longer and heavier lenses, like an AF-D 180mm f/2.8 or an AF-S 24-70mm f/2.8: it takes away the stress from the camera mount and results in a better balance on the head. When the lens has its own tripod attachment, of course it is best to use that one.

The mount does not rotate for shooting in vertical orientation, something that is possible (but not always practical) with the optional and expensive tripod mount for the Novoflex adapter.

Metabones states that the tripod foot is detachable. Well, it is in the sense that it just takes a (2.5mm) allen key or wrench to remove the two holding screws and release the mounting piece.

With the F-to-X and G-to-X adapter however, that leaves you with two gaping holes that will let light into the system (unless gaffer tape comes to the rescue once again).

The Speed Booster is the exception: it ships not only with the required allen key but also with two small plastic plugs to cover the screw holes (as mentioned above). It seems to be a small effort for Metabones to fix this inconvenience and add at least the two caps to each package, but I expect that most people – including myself – will simply leave the tripod foot in place.

Features and operation

The Metabones F-to-X adapter accepts virtually any lens with a Nikon F-mount, including pre-AI, AI, AI-S, AF and AF-D lenses. G-type lenses do not have an aperture ring on the lens and can be mounted but will remain set to their smallest aperture setting (highest f-stop number) making them virtually useless. The G-lens group includes all AF-S and all DX lenses. I have not yet found any non-G lens that did not work on this adapter; the oldest one I tried is a pre-1970 Nikkor H 50mm f/2.0.

The Metabones G-to-X adapter and the Nikon-to-Fuji Speed Booster are equipped with an aperture control ring on the adapter, which makes them compatible with G-type lenses as well. We will discuss the operation of this control ring later in great detail.

None of these adapters provide any form of mechanical or electrical communication between lens and camera. This implies that:

• Focus is always fully manual;
• Exposure modes are limited to A (aperture priority) and M (manual);
• Viewing and metering will be at the effective aperture set either on the lens or via the adapter’s ring;
• VR is not available;
• No lens data will be passed on to the camera, so the EXIF data in the recorded image will at best be incomplete.

Make sure that SHOOTING MENU > SHOOT WITHOUT LENS is set to ON, otherwise no pictures can be taken. To pass on the focal length of the mounted lens to the EXIF data, select one of the six settings in SHOOTING MENU > MOUNT ADAPTER SETTINGS (remember that you can modify the last two settings at will).

OVF framing is possible on the X-Pro1 with lenses from 18mm to 60mm (provided that the focal length information is entered correctly). Focusing will usually rely on using either the EVF or back LCD in combination with the 3x/10x magnification and/or focus peaking capabilities. Older lenses usually have a smooth manual focus ring with a generous control range; many also have a depth-of-field scale making focus presetting or zone focusing feasible.

Viewing and focusing at the effective shooting aperture has the advantage to give a realistic depth-of-field preview, but requires boosting the EVF/LCD gain for an enhanced image, thereby increasing viewfinder lag. Opening the lens aperture to its maximum for composing and focusing clearly increases the viewing comfort and focusing precision, but don’t forget to return to the working aperture afterwards!

Finally, remember that the information from the live histogram is not reliable in M mode, and also not with a dark subject image (or a lens manually set to a narrow aperture).

NEXT: the wonders of the Speed Booster optics

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The Fellowship of the Ring(s)

or: How I Learned to Stop Pixel Peeping and Love Old Glass

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One of the additional rewards of working with a Compact System Camera (CSC) lies in the ability to use other lenses beyond those directly available in your camera’s mount. Many more lenses, actually, as with a little investment and effort you can have access to literally hundreds of optical masterpieces originally designed for SLR and DSLR cameras. In most cases however, only as long as you are willing to forsake some (or most) automated features that come standard with recent models.

No more automatic aperture control (which allows viewing and metering at the lens’s maximum aperture, stops the lens down to the working aperture during exposure, and returns the lens to maximum aperture after exposure). No communication between lens and camera body (to pass on focal length, aperture or distance information). No more autofocus. And certainly no vibration reduction/image stabilization. Although, because every rule requires an exception, some DSLR manufacturers offer an adapter – only for lenses from the same brand – that does preserve several functions when used on their own CSC models.

Less is more

How do we make CSCs compatible with (D)SLR lenses?

 

 

The diagram gives the schematic of a DSLR camera in (1), with the essential components of its reflex viewfinder system: a mirror and a pentaprism. The design of the associated lens is matched to the mechanical dimensions of the camera system. Specifically, the lens mount is expected to be positioned exactly at the focal flange distance or register distance d1 from the camera sensor.

As shown in (2), the CSC design gets rid of the large mirror box – it makes them mirrorless. As a result, the lens mount can get closer to the camera sensor: the register distance now has a lower value d2. That makes it possible to develop more compact and lighter camera bodies, as well as smaller and lighter lenses dedicated to this system.

In order to make a (D)SLR lens focus correctly on the CSC sensor, the original register distance d1 must be restored: that is the main task of the lens mount adapter (LMA), which as illustrated in (3) inserts between lens and camera.

 

 

Among the current (D)SLR classics, the Nikon F-mount has the longest register distance with 46.5mm, whereas the shortest distance is found at 44mm with Canon’s EF(-S). As for the popular CSC brands, Micro Four Thirds (MFT) has the longest register distance with 19.25mm, then come the Sony NEX E-mount and the Canon EF-M both with 18mm, then the Fuji X-mount with 17.7mm, and finally Nikon 1 with 17mm. The difference between the register distances for (D)SLR lenses and popular CSC models makes it at least mechanically possible to build an adapter for coupling them.

Of course, the image circle projected by the lens at its designated register distance must be large enough to fully cover the CSC sensor. If not, strong vignetting will occur. In most cases, a lens originally designed for use on 35mm film or full-frame or APS-C crop digital reflex cameras will be mounted on a CSC with an APS-C or smaller sensor. The only remaining issue then is the “cropping” of the lens image by the reduced size sensor, reducing the effective angle-of-view of the lens.

The lens adapter: functions and features

Here is what a lens adapter should do, for example to use a Nikon lens on a Fuji X camera:

• Enable the mechanical coupling of a lens and a camera body, using the appropriate mounts at each end of the adapter: a Nikon F body mount at the front, a Fuji X lens mount at the back;
• Restitute exactly the original focal flange distance the lens was designed for, so that a sharp image can be obtained over the full focusing range (including infinity): in this case this means adding 46.5mm -17.7mm = 28.8mm;
• When and if possible, support relevant electrical or mechanical communication between lens and camera body (to assist with aperture control, autofocus, VR/IS, record lens data…): alas no such opportunity in our example;
• When required, provide an alternative way to control the lens aperture setting from the adapter, if the lens itself does not have an aperture ring and the abovementioned communication between lens and camera is not possible: the blue ring on the Novoflex FUX/NIK adapter in the picture provides this for Nikon G-type lenses (including AF-S and DX models);
• Optionally, have a tripod mounting support that comes handy for mounting longer and/or heavier lenses: the Novoflex adapter has this as an option.

In addition, some adapter models come with creative ways to take good advantage of the ‘missing’ register distance that needs to be added:

• Some offer tilt, shift or combined tilt/shift mechanisms, turning the setup into a very portable view camera;
• Some add optical elements into the adapter to reduce the resulting focal length (virtually eliminating the crop factor) as well as boost the light gathering power.
  

Why use a lens adapter?

Lenses designed specifically for your CSC in most cases will be the preferred option: they are lighter and more compact, usually offer autofocus and sometimes image stabilization, support all camera shooting modes, communicate information data for inclusion with the EXIF data, and are computer designed with the most recent optical formulas and materials. Fujifilm XF-lenses certainly belong to the best you can get, and companies like Zeiss and Samyang offer interesting complements.

So why would you decide to work without the benefits of modern lens technology?

• The lens choices offered within your CSC system may be limited; for a Fuji example: there was no wide-angle wider than 28mm (FF equivalent) until the XF 14mm appeared, no long tele option before the XF 55-200mm, and still no fast portrait lens while we wait for the pre-announced XF 56mm f/1.2;
• If – like me and many others – you have been shooting (D)SLRs for a long time, you may own an assortment of lenses for that system, often manual focus primes: there are great to use with your CSC until an appropriate ‘contemporary’ alternative becomes available, or you simply can save some money if you do not often use that focal length;
• Some of these older lenses may take a special place, because of their specific image rendition characteristics, or just for the memories: it is always a pleasure to ‘revive’ them;
• If you are into close-up or macro photography, you can find and use accessories like extension rings and bellows (these are seldom available with today’s CSC systems);
• Extra features of the lens adapter, such as a tilt and/or shift capability, open new shooting opportunities at a minimal investment;And probably some more that may be relevant to you…
  

Guilty as charged

While I gradually switched to the Fuji X-system, I thinned my Nikon collection, keeping one full-frame body, three f/2.8 zooms and a lot of primes. The lenses are made by Nikon and by third-party suppliers and span the range from 17mm to 200mm. Some are fairly recent and others are with me since the early 70s. It would truly be a shame to let these lenses sit in the drawer and gather dust. There’s so much photographic delight left with them!

I currently own no less than 9 different adapters for combining Nikon F-mount lenses with Fuji X-mount cameras (no, my second name is not Imelda). They represent the entire range of available adapter types, as far as I am aware. And then one more, for Leica legacy lenses with a 39mm screw thread.

In follow-up blog posts, I plan to offer extensive reviews of all of these. To begin, we will have a thorough look at the top-end models from Metabones, including their amazing Speed Booster. I know that some of you are waiting to hear more about these!

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