Because we can!

When total strangers meet…

Click on any image to see a larger version

What can you possibly expect when hooking up a camera, a lens and some accessories that were never intended to even meet? It would be rather foolish to presume that their individual designers worried for a moment about possible incompatibilities and unwanted interactions…

And yet, once in a while, the unexpected happens and you’re left with an intriguing combo to explore and enjoy!

Stage left: the Fujinon Teleconverter XF 1.4x TC WR

Last October, Fujifilm announced a 1.4x teleconverter adapter, a high-quality and high performance optical accessory that multiplies the focal length of the attached lens by 1.4x. As the imaging circle is enlarged (its surface area doubles) there is a one stop loss of light transmission. A series of firmware updates for the various X-bodies ensures that the recorded EXIF information reflects the actual aperture and focal length when the TC is used.

A 1.4x crop may not seem much, but all help is welcome with a 16Mpx sensor…

The combination of the 1.5x APS-C sensor crop factor and the 1.4x TC magnification results in a final ‘35mm FF equivalent’ focal length of 2.1x the original lens value.

At this moment, the XT 1.4x TC can only be used with the XF 50-140mm f/2.8 zoom. The combo becomes a 70-196mm f/4 zoom lens (covering the same angle of view as a full-frame 105-294mm lens). We can however expect additional compatibility with the XF 100-400mm super-tele zoom and XF 120mm macro lenses that will challenge our lens lust (and bank accounts) sometime during 2016.

The XF 1.4x TC sitting where it currently belongs: behind an XF 50-140mm tele zoom

There are countless reviews documenting how well the TC 1.4x/50-140 combination performs optically. Suffice to say that my own quick-and-dirty tests fully confirm this.

100% center crops with and without the 1.4x TC (click on image for larger version)

Besides any possible optical considerations, it is physically impossible to mount the TC to any other current XF lens. The front part of the TC extends significantly forward from the lens mount, and requires some ‘opens space’ at the back end of the to-be-mounted lens. Obviously, the design of the XF 50-140mm accommodates for this (and so will – at least – two of the future ones) but none of the other available XF lenses will work…

Now, if any other lens came with both an XF mount AND sufficient open space at the back to receive the TC’s protrusion, would it then be possible to make use of the teleconverter…?

Stage right: an adapted legacy lens

When I first saw images of the XF 1.4x TC and noticed its unusual shape (compared to traditional TC designs), I vaguely remembered a post I stumbled upon a few months earlier on a Micro Four Thirds forum. The Olympus M.Zuiko MC14 indeed has a very similar construction.

Ever since acquiring a Fujifilm X-Pro1 in early 2012, I have used a number of F-mount lenses collected over 40+ years of shooting with Nikon SLRs and DSLRs. In case you are interested: more info on this introduction to adapted lenses, and this full overview of Metabones adapters.

A mount adapter enables the use of ‘legacy’ lenses on recent system camera bodies. The classic (D)SLR design requires a fairly large flange (i.e. film/sensor-to-lens mount) distance to make room for the reflex mirror box. With mirrorless cameras, the lens mount sits a lot closer to the sensor. A basic lens adapter compensates for the difference by providing additional spacing between the respective lens mounts. For a Nikon F to Fujifilm X mount adapter, that distance must be exactly 28.8mm.

The above image clearly shows that the (otherwise hollow) adapter provides ample space to accommodate the TC’s extending front section. Once the adapter is attached, the TC sits well behind the F-mount and does no longer requires a specific lens construction.

Obviously, there will be no electrical communication possible between lens and camera body, and we will not have any actual lens and aperture information embedded in the EXIF data. Nothing different here compared to the ‘regular’ use of such a lens adapter. However, metering in A and M modes as well as all forms of manual focus assistance remain fully operational. Great to discover that a camera-with-TC does not get confused when no XF lens is attached!

Solving the mechanical compatibility of course does not guarantee that we can expect a great or even acceptable optical performance. We are combining components that were originally designed for use in totally different circumstances. I don’t know of any teleconverter design that was not optimized for a specific and limited range of (mostly tele) lenses. And I am pretty convinced that none of the Fujifilm engineers even for a brief moment worried about such an exotic line-up!

With that in mind, I was more than curious to have a look at my first test images.
All ye who enter here, abandon hope…

First test: some ‘normal’ primes

I honestly did not have any expectations at all for this initial quick assessment. We all know that TCs are traditionally intended for use with tele lenses. So why even bother to snap on a cheap mid-80’s Nikon AF 50mm f/1.8 (pre-D) and a slightly more recent Nikon AF-D 85mm f/1.8?

Surprise!

Have a look at these images and 100% center crops, shot in my familiar light tent studio, at distances around 70cm resp. 100cm. For all of the comparison shots following, both versions have been processed with identical Lightroom settings. (click on any image for a larger version)

Nikon AF 50mm f/1.8 with XF 1.4x TC

100% center crops with TC, at f/1.8 resp. f/4

Nikon AF-D 85mm f/1.8 with XF 1.4x TC

100% center crops with TC, at f/1.8 resp. f/4

With a little stopping down, you get perfectly useable image quality (remember for exposure calculation that with the TC the actual aperture is one stop slower than set on the lens).
No visible signs of vignetting or aberrations, in fact a very similar optical performance as the original ‘naked’ lens.

As the available range of Fujifilm XF lenses grows (with some additional gap fillers from third parties), my regular use of adapted lenses has substantially diminished. Except for a few ones, for which there are still no alternatives with an X-mount. So let’s have a look at two more legacy primes that frequently find themselves onto my X cameras.

Second test: a trusted macro lens

I bought a Tamron 90mm f/2.8 SP Di Macro lens (with Nikon F-mount) in 2004, and have used it extensively ever since. It is an extremely sharp lens, that offers a generous working distance even at extreme close-up range. The longer focal length, the 1:1 capability and the generous manual focus ring are three reasons for giving it ample show time next to my beloved XF 60mm. The only X-mount alternative is the Samyang 100mm f/2.8 Macro, but that one does not offer enough value added to consider a switch. So, for now the Tamron 90mm it is (until perhaps I give in to the XF 120mm?).

If this lens would still perform in combination with the XF 1.4x TC, it would bring an increased 1.4:1 magnification without sacrifying shooting distance.

The Tamron 90mm f/2.8 SP Di Macro ready for action

I will let you be the judge on the results of a quick macro test. I used reasonable care to make good shots (solid tripod, manual focus assist, electronic remote, self timer…) without spending too much effort. My subject was a 29mm x 25mm postage stamp; the actual width of the word ‘BELGIË' is 7.5mm, the circle around the ‘1’ has a 4mm diameter. As always, clicking on an image presents a larger version in a separate window.

Full image without TC

Full image with TC

100% center crops compared

There is a little loss of micro contrast, requiring nothing more than a small nudge to the Clarity slider. No sign of visible vignetting or serious corner sharpness degradation. My conclusion: whenever I hit the need for the extra magnification, I will not hesitate to put the XF 1.4x TC behind this lens!

I also did a quick test on a distant subject (about 150m from my shooting position):

Full image without TC

Full image with TC

100% center crops compared

A nice result as well.

Third test: a classic tele

I have always liked Nikon’s AF-D 180mm f/2.8 IF ED. I owned a neat second hand copy, sold it later (as I felt I wasn’t using it often enough on my D700) but ended up acquiring another used copy, one in even better condition. This medium tele lens is tack sharp even fully open, and has a nice micro contrast.

I started taking a look at the same distant subject as above:

100% center crops (without and with TC) compared

100% center crops (with TC and lens set at f/2.8 resp. f/5.6) compared

The 180mm + TC on an X camera delivers an angle of view close to a 400mm f/4 lens on a full-frame body. As expected, a stopping down 1 or 2 stops and adding a little Clarity leads to more than acceptable results. At f/2.8 this lens shows visible chromatic aberration; adding the TC makes it a little worse; by f/5.6 it is already significantly reduced. Again, nothing that Lightroom cannot easily correct for.

I next pointed my camera towards a subject at medium distance (some 25m):

Full image without TC

Full image with TC

100% center crops (without and with TC) compared

100% center crops (with TC and lens set at f/2.8 resp. f/5.6) compared

Finally, I was curious about the close-up performance of the 180mm + 1,4x TC combination. I took the following shots from about 1m distance:

Full image without TC

Full image with TC

100% center crops (without and with TC) compared

Conclusion – and why bother?

All of the above is far from a stringent, carefully controlled optical test. Frankly, the whole idea of using the XF 1.4x TC in combination with an adapted legacy lens is a bit ‘exotic’ to begin with… and therefore perhaps not worth much more effort J

My experiments indicate that more than reasonable image quality can be obtained with a broad range of non-Fujifilm lenses. That by itself is a remarkable outcome, and probably points at a very ‘robust’ optical design of the teleconverter. If true, that offers the perspective for many more useful (and designed for) lens combinations in the future. How about that?

Beware to extrapolate my findings to any other TC/lens combinations! Please do realize that any decent result is nothing more than a collateral by-product of the TC ‘s design targets.

If you happen to own an XF 1.4x TC, as well as some legacy lenses and an adapter with sufficient physical depth, please go explore! You may discover a handy stopgap solution here and there, while we wait for an even more complete XF lens line-up. I have little doubt that I will still use these legacy lenses once the 120mm macro and a 100-400mm tele zoom become available (and part of my glass collection): in the long term autofocus and image stabilization will prevail, even when coming at the cost of one f-stop or so. But until then…

So why again do we even bother testing these weird combinations? Because we can, of course, and because it’s a lot of fun as well!

Click on any image to see a larger version

Metabones Nikon F to Fuji X adapters – UPDATE

Two years later: where do we stand?

Click on any image to see a larger version

In August/September 2013, I published an extensive review of the Metabones adapters for mounting Nikon F-mount lenses onto Fujifilm X camera bodies, including the Speed Booster focal reducer model, as a series of eight blog posts:

• Introduction to lens adapters
• Metabones Nikon F to Fuji X adapters
• The Metabones Speed Booster
• The Metabones approach to aperture control
• Speed Booster image sharpness evaluation
• More Speed Booster sharpness tests
• Other Speed Booster image quality tests
• Metabones Nikon F to Fuji X adapters – Conclusions

This July 2015 update covers some relevant developments since that time.

Speed Booster ULTRA: improved optical performance

In September 2014, Metabones announced an ULTRA version of its APS-C Speed Booster models with a new optical design - 5 elements in 4 groups - incorporating ultra-high index tantalum-based glass to achieve improved corner sharpness, distortion and reduced vignetting.

The original Metabones Speed Booster, announced in January 2013, counted 4 elements in 4 groups. Both versions share the same 0.71x magnification, and so reduce the crop factor of  Fuji X-mount cameras from 1.5x to 1.07x.

The new optical formula significantly improves corner sharpness and reduces vignetting when using lenses with a longer exit pupil distance, such as ultra-high speed (f/1.2 and below) primes and pro-grade f/2.8 zooms.

Simply stated, the exit pupil is the virtual image of the aperture stop as seen from behind the lens. The distance between the exit pupil and the sensor plane determines the range of angles of incidence of the light rays hitting the sensor. The closer the exit pupil to the sensor, the higher the angles of incidence at the edges of the field, and the higher the risk for pixel vignetting. Note that exit pupil distance and focal length are completely unrelated: all depends on the specific optical design.

Most classic SLR lenses have an exit pupil distance in the 50-90mm range. The original Speed Booster gives excellent results with exit pupil distances up to 100mm. The ULTRA extends the exit pupil range out to about 150mm, and delivers visible improvements from about 90mm onwards. Popular Nikon lenses that will benefit from this include the AI-S 50mm f/1.2, the AF-D 105mm f/2.8 Micro and the ‘holy trinity’ zooms (AF-S 14-24mm f/2.8G, AF-S 24-70mm f/2.8G and AF-S 70-200mm f/2.8G VR types I & II).

Note that my earlier tests clearly demonstrated this significant pixel vignetting effect with the AF-S 70-200mm f/2.8G VR (type I).

All N/F-X adapters: improved aperture control mechanism

One review section, The Metabones approach to aperture control, dealt with the operation of the aperture ring available on some adapter models - including the SpeedBooster version - to control the shooting aperture when using G-type lenses (the ones that don't come with their own aperture ring).

As noted in the review, the original mechanism does not provide a linear control action: (half) steps on the aperture ring do not correspond to equally spaced changes in the lens aperture. This significantly complicates the process of manually setting a precise aperture value.

With the release of the SpeedBooster ULTRA version, Metabones has changed the aperture control mechanism and the control ring marking on both the Speed Booster ULTRA and the ‘glassless’ Nikon-F-to-Fuji-X adapter. The image below shows the original version of the latter at left, and the updated version at right.

It is immediately clear that the aperture scales have changed. For some reason, the lettering moved from ‘F-2-3-4-5-6-7-8’ to ‘F-1-2-3-4-5-6-7’. Perhaps this is an attempt to more clearly indicate the amounts of f-stops down from the fully open aperture position (but, as we will discover, that doesn’t hold…)?

The original version has 15 well-defined click stops. The revised version no longer has discrete click stops, no doubt to facilitate the continuous aperture changes desired by videographers. The unit however is shipped with the necessary extra hardware parts to ‘install’ a click system should the user so desire (instruction videos are available on YouTube).

More importantly, Metabones radically changed the mechanism that drives the aperture control lever at the back of a Nikon F-mount lens.  The original rotating actuator is replaced by a sliding tab, that provides the linear motion AI-S and later Nikon lenses expect: the aperture lever travels the same amount for every f-stop.

old at left, new at right

The difference in operation is best shown by this stop-motion animation:

 old above, new below

I had the opportunity to have a thorough look at the new design, as one of my friends kindly loaned his copy (thanks, Wim!).

I measured the effect of the adapter’s aperture ring position on the lens aperture using both the old and the new Metabones adapters, using four prime lenses (Nikon 50/1.4, 50/1.8 and 85/1.8 AF-D’s, and my trusted Tamron 90/2.8 macro), with the following result:

Note that some of the jitter of the ‘new’ curves may come from the fact that it now is harder to precisely set (or repeat) an aperture value, due to the now click-less control ring.

After averaging each set of curves, we find the following:

It is more than clear that the new aperture control design results in an almost perfectly linear action, with a maximum of about 6 f-stops down from the fully open value (which of course depends on the attached lens). There is still the half-stop ‘loss’ at the beginning of the curve.

The linear behavior makes it a lot easier to work with G-type lenses (without aperture ring). Of course, I still prefer shooting with older lenses that have their own aperture ring.

Click on any image to see a larger version

Metabones Nikon F to Fuji X adapters – Conclusions

Three steps to heaven – and a few pitfalls along the way…

Click on any image to see a larger version

Over the past few weeks, I took an in-depth look at the various Metabones lens adapters for Nikon lenses, and at their remarkable Speed Booster model in particular. What started as a simple evaluation – do these lens adapters live up to their claims and to my expectations? – ended up with a comprehensive series of test shootings.

More details can be found in the following earlier blog posts:

• Introduction to lens adapters
• Metabones Nikon F to Fuji X adapters
• The Metabones Speed Booster
• The Metabones approach to aperture control
• Speed Booster image sharpness evaluation
• More Speed Booster sharpness tests
• Other Speed Booster image quality tests

My experiments are limited to the combination of Nikon (and a few third-party) F-mount lenses and a Fujifilm X-mount camera. Note however that the Speed Booster optics tested here are identical to the Sony NEX version, as both cameras use APS-C sized sensors.

 

What did I learn from my test images?

To start, a number of positive conclusions that confirm the manufacturer’s claims:

1. Using a full-frame lens on a Fuji X (APS-C) camera, the Metabones Speed Booster nearly restores the “original” field-of-view and depth-of-field experience of working with a full-frame camera

The final overall crop factor is reduced from 1.5x to 1.07x (rounded), meaning a 50mm lens on a Speed Booster will deliver the field-of-view equivalent to a 53mm lens. The corresponding shallower depth-of-field and bokeh rendering are available again as well.

X-Pro1 + Speed Booster + AF-S 50mm f/1.4G set to f/1.4

2. The Metabones Speed Booster adds one full f-stop in light capturing performance

A 50mm f/1.4 lens becomes a 36mm f/1.0; an 85mm f/1.8 turns into a 60mm f/1.3, a 180mm f/2.8 acts like a 128mm f/2.0… Great news for low-light shooters!

A discussed later however, with some lenses the available f-stop range may end up slightly reduced.

X-Pro1 + Speed Booster + AF-D 20mm f/2.8 set to f/8

3. The Metabones Speed Booster delivers excellent image quality

A large selection of lenses likely to be combined with a compact system camera shows a similar to slightly better optical performance in the center of the frame. The corner performance turns out to be similar to slightly lower (especially at wider apertures), and varies more with the specific lens itself.

All things considered, I can only conclude and confirm that the Speed Booster does not significantly degrade the performance of the attached lens (as some forum and blog posts sometimes suggest). This holds true for sharpness, vignetting, bokeh rendering, color fringing…

The characteristics of the lens attached of course play a big role, and so does its condition when it’s an older, well-used copy. Furthermore, you need to compare apples to apples: it makes little sense to put side-by-side images shot using the full-frame area with others from a crop sensor using only the center area of the lens, or with pictures made on a full-frame camera with its built-in image correction features enabled.

X-Pro1 + Speed Booster + AF-D 180mm f/2.8ED set to f/4

There are also a few minor negative remarks, all related to the operation of the aperture control ring shared by the Speed Booster and the Nikon-G-to-Fuji-X adapters:

4. The aperture ring scale is neither linear nor uniform with respect to actual f-stop settings

The Metabones website claims: “Industry's best aperture ring covers an 8-stop range with half-stop markings, clearly indicating actual number of f-stops. No more guesswork!”

In reality, you do get 15 clicking positions, but not 15 half f-stop settings as the wording may suggest. The aperture increments are not equally spaced across the available f-stop range of the lens: the step values are bigger at the open aperture end and decrease towards the smaller apertures.

You can use my “magic numbers” scale to perform the translation:

5. You may not be able to use the full aperture range originally offered by the lens

The aperture ring design limits the control span to about 6 f-stops only (starting from fully open). If your lens offers more, the smallest f-stop(s) will no longer be available.

In addition, with some lenses (or lens/adapter combinations?) the fully open iris position may not be reached, losing ⅓ to ½ stop at the wide open end. That takes back a little from the one f-stop gain, at least for who is looking to shoot with a minimal DOF. Note that this is often also the case with other adapters equipped with a different form of aperture control mechanism.

If – like myself – you mostly have F-mount lenses that do have an aperture ring, you might have preferred a Speed Booster version without aperture control on the adapter…

Both “negatives” will likely not have a major impact on real-life use, as the smallest aperture settings are generally avoided, in light of diffraction effects.

Are the Metabones lens adapters worth the investment?

The manufacturing quality of the Metabones adapters is simply best-in-class. Each adapter is precise, well-finished, robust, and a pleasure to operate. The Arca-compatible tripod mount is a nice feature, certainly with heavier or longer lenses.

Looking at the Speed Booster, the resulting images come very close to the “experience” obtained with a full-frame camera, and the image quality of the attached lens is largely preserved. The extra f-stop is a welcome addition to that. The Speed Booster helps to fill gaps in Fujifilm’s current XF lens line-up, at least until new lenses are added to the roadmap and become available (and the extra cash is spent).

In the end, the added value of a Speed Booster will vary from user to user. How extensive is your Fujifilm XF/XC lens collection, and how wide and fast will you let it grow in the future? How many Nikon F-compatible lenses do you already own, or do you plan to acquire some mint used copies to extend your lens line-up? Questions only you can answer for yourself…

The three Metabones lens adapters have found a warm place within my X-camera system. I use them on a regular basis with primes between 17mm and 180mm. The Speed Booster has opened up interesting opportunities, especially with fast lenses in the normal to short-telephoto focal range. Some of that may change when Fujifilm releases new XF lenses – the XF 56mm f/1.2 comes to mind immediately. But I guess all three adapters I acquired – and the Speed Booster in particular – will see plenty of action in the coming months.

Click on any image to see a larger version

Metabones Nikon F to Fuji X adapters – part VI

Image quality reporting continued

Click on any image to see a larger version

 

TEST THREE: vignetting

Does a Speed Booster cause a visible increase in lens vignetting?

Most lenses show some noticeable level of vignetting at open and wide apertures. We all know that, and this effect was clearly present in the samples presented before. Furthermore, fast (f/1.4) lenses are known to suffer from vignetting more than others.

When (Nikon) lenses are mounted on lens adapters, there is no information about the working aperture passed on electronically to the camera. As a result, there is no in-camera image processing to compensate e.g. for vignetting, nor is any information included in the associated EXIF data to control compensation in post-processing software. In other words: the correction of vignetting, distortion, chromatic aberration and any other undesired effect is fully left with the photographer.

Today we all are used to cameras and workflows that silently take care of these matters – directly, or in post. And indeed, so do Fujifilm X-cameras when coupled with XF/XC lenses. So we easily forget that our DSLRs as well include some corrective image processing that we take for granted.

A Nikon camera like my D700 has a built-in vignette compensation that impacts the RAW (NEF) files. To make camera-to-camera comparisons a bit fairer, I have disabled this function on my D700 for these vignetting tests.

Images from various test series indicate that the level of vignetting with the same lens attached to an X-camera with Speed Booster or used directly on a DSLR (with vignetting control disabled) is very comparable. The composite image below shows the corner shading of the AF-S 50mm f/1.4G at various apertures on both camera configurations, and again illustrates the virtually identical vignetting effect:

We can conclude that – at least with this lens – the Speed Booster does not introduce any significant additional vignetting. That also means that whatever corner shading remains can easily be eliminated (if desired) through normal post-processing actions.

In the Speed Booster white paper and in follow-up discussions on forums, Brian Caldwell explains that the corner performance of the Speed Booster depends on the exit pupil distance of the lens. The exit pupil is the virtual image of the iris opening in an optical system as seen from whatever comes behind it. The exit pupil distance is not directly related to the focal length, and – unfortunately – is hardly ever documented within the lens specifications.

The optical design of the APS-C Speed Booster (shared by the Fuji X and Sony NEX mount versions) is optimized for lenses with an exit pupil distance in the 50-85mm range. This is perfect for most wide-angle, normal, and some short telephoto SLR lenses. Lenses with exit pupil distances beyond 100-110mm can be expected to show weaker corner performance. Here we can start seeing "hard" vignetting in the extreme corners, especially at small apertures. Longer telephoto lenses usually fall in that category, but there are also some examples at shorter focal lengths.

Only one lens in my test set showed a severe problem: the AF-S 70-200mm f/2.8G VR (first generation). The collection of test images below shows dark areas in the corners that do not disappear when closing the aperture, but rather become more sharply delimited. The effect is visible at all focal lengths across the zoom range, and does not seem to vary with the focus distance either.

It is possible that with the 70-200mm something is blocking part of the exit pupil image to properly hit the Speed Booster optics. The rearmost optical element of that lens indeed lies rather deep into the barrel. But no visible corner clipping occurs with the AF-D 180mm f/2.8ED, even though its rearmost element lies even deeper.

TEST FOUR: bokeh

One of the more attractive benefits of the Speed Booster is restoring the narrower depth-of-field (DOF) as experienced with full-frame lenses with full-frame sensor cameras, and with that the creation of a pleasing creamy bokeh in the out-of-focus areas.

What is the effect of the Speed Booster optics on a given lens’ bokeh? I have evaluated this using another simple but colorful test scene, with plenty of reflective materials.

Here are the results (and 100% crops) comparing the bokeh of a number of lenses when used directly on a D700 to the bokeh obtained with an X-Pro1/Speed Booster combo, starting with the AF-D 50mm f/1.4:

Next, looking at the AF-D 85mm f/1.8:

And finally the results for a longer telephoto lens, the AF-D 180mm f/2.8ED:

Conclusion: there is no significant change to the bokeh rendering of (at least these tested) lenses when used with a Speed Booster.

TEST FIVE: bokeh fringing

Bokeh fringing is caused by longitudinal chromatic aberrations (non-coinciding focal planes of the various colors) and is a common issue with relatively fast glass. The halos surrounding out-of-focus hard edges have different colors - magenta in front of the focus point and green beyond.

To learn more about this type of potential image degradation, I captured images from a SpyderLENSCAL autofocus alignment target for just a few lenses. The camera position was changed for each half image in the pair to have the same area reproduced in the crops. Only the center of the frame was examined. Note the shallower DOF in the Speed Booster images (left parts).

The results speak for themselves: no significant (center) quality loss from the Speed Booster.

TEST SIX: color reproduction

Every optical element we add to the system may alter the color reproduction characteristics of the overall system. I captured an X-Rite ColorChecker Passport target with and without the Speed Booster. White balance was taken from the left image, and the color temperature and tint values were transferred to the right (Speed Booster) image.

The Speed Booster introduces a very light orange cast. In Lightroom, it takes just a -50 temperature, -3 tint adjustment to optimally white balance the Speed Booster version. No obstacle in any post-processing workflow!

 

TEST SEVEN: infinity focus

It is very important that a lens adapter offers an absolutely correct (and uniform) flange focal distance. If the register distance is too long, it will no longer be possible to focus a lens at infinity.

The presence of optical elements in the Speed Booster potentially could further introduce problems.

I have not found any issue with any of my 20+ lenses checked.

(Note that it is important not to confuse matters here: infinity focus problems mean that you cannot anymore obtain a sharp image from very distant subjects. It does NOT mean that you can simply align the infinity symbol to the focus mark on your lens and count on having a sharp picture. Many lenses – and certainly older ones – may have their true infinity position before or even beyond the infinity mark.)

Even if an issue would be found, the Metabones web page describes a procedure to manually adjust infinity focus for a specific lens (risking however to make things worse for most if not all others…): the Speed Booster optics can be moved inside the housing after loosening a locking screw. Only for the brave of heart!

 

NOT TESTED: distortion

In a forum post, Brian Caldwell indicated that the APS-C Speed Booster adds about 1.5% of barrel distortion. That is not a lot, but if the attached lens already has barrel distortion things obviously gets worse (if the lens has pincushion distortion, the Speed Booster may actually correct it).

I did not come up with a simple test to verify this statement.

NEXT: The Final Verdict on the Speed Booster

Click on any image to see a larger version