All about that Hood

Pimp your XF lenses!

Thanks for the many comments and suggestions! I have (twice now) updated this post
with a quick overview table (at the end), and added a few clarifications here and there.

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Let’s be honest: next to the ease-of-use of the Fujifilm X cameras, the advantages of their sensor, the performance of the XF glass and the resulting image quality, many X-shooters just love the retro design and handling of the bodies. Right from the start, with the original X100, we got a compact tool to completely enjoy taking pictures. If you’re old enough to have started photography with roll film or 35mm cassettes: just add “again” at the end.

In order to augment the “old days” experience, we’ve been adding leather carrying and wrist straps, half cases, thumb grips, soft releases, old-fashioned cable releases… In the end though, you can’t but ask yourself:

Why didn’t Fujifilm bring us sexier lens hoods?

It started rather well actually. The X100’s fixed 23mm lens comes with a nice metal vented release. That comes handy when using the optical viewfinder, as less of the field of view is obstructed (as long as the openings are well aligned, hence the bayonet mount).

Then, the XF 18mm f/2.0 and XF 35mm f/1.4 (both part of the X-Pro1 release wave) came with somewhat classy rectangular metal hoods, alas also with horrible rubber front caps.

After that, sadly, we saw the typical petal shaped or (rather oversized) cylindrical lens hoods coming over from the (D)SLR market…

There’s a lot of good things to say about the Fujifilm lens hoods though. They do come included with the lenses, and provide more than adequate light shielding and protection for the front lens element. They can be mounted reversed to save space in your bag, and are made of solid mass-colored plastic to resist dents and scratches (the 18 and 35 metal ones are the exception for both last attributes).

But they remain cumbersome, tend to come off or knock loose when banging around in crowds, are a pain to mount/unmount when changing lenses, and look quite a bit, well… boring.

It’s not all that bad, is it?

Fortunately, there are plenty of alternatives available. Some come from traditional third party accessory brands, others spawn out of Chinese workshops courtesy of eBay.

As I was gradually building up my lens collection for the X-cameras, I constantly looked for and experimented with alternative and mostly classic-styled lens hoods. The ones that I have and use are all sturdy one-piece metal designs, with a screw mount in the matching filter thread size. Screw-on hoods have the advantage that they stay firmly in place even when things go hectic around your camera. Read: street photography, event coverage, reportage…

These hoods are anodized black, with a satin finish on the outside and a grooved matte finish on the inside, the latter to reduce internal reflections. They have proven to resist well against dents and scratches, I cannot see much wear other than along the front outer rim: in that they perform at least as well as any other metal hood I used throughout the (many) years.

As you can see above, the hoods come in different versions, each available in various sizes:

• a vented design, approximately 18mm long, with three* slots (model MH-xx);
• a standard cylindrical one, approximately 20mm long (model MH-xxS);
• a tele cylindrical one, approximately 35mm long (model MH-xxT);
• a wide tapered version, approximately 18mm long (model MH-xxW).

I order my lens hoods directly from Hong Kong based eBay vendor gadgetworldexports. They have proven to be very reliable, supplying correct information, and offering free and fast standard shipping (about twice as fast to Belgium as any other HK/China outlet I ordered from). Never had any issue whatsoever.

After a lot of small yellow packages in the mailbox, I now have a broad collection in thread sizes from 39mm to 72mm (the ‘xx’ in the model designation). Unit prices ran between USD 3.49 and USD 5.99, shipping included – so nothing to break the bank. No fear for damaging or losing.

* A keen observer on some of the images that one of the vented hoods shows not three but five “vents”. The very first vented hood I purchased (early 2012, a 52mm model to go on the XF35) indeed came from a different eBay vendor and has a slightly different design.

More form than function

I don’t want you to get all carried away, now… Remember that the length of any symmetrical lens hood should not exceed the minimum depth of the Fujifilm petal hoods, or else corner vignetting may pop up (after all, that’s what the originals were dimensioned for).

Also, whereas screw-on filters can be added without changing the position of a bayonet mounted hood, they will take up space between the lens thread and the screw-on lens hood: that too may lead to vignetting. Take this into account when combining screw-on hoods with screw-on filters!

Finally: you can put lens caps on the hoods for extra dust or impact protection, e.g. inside a carrying bag. I recommend to use appropriately sized snap-on or pinch-type caps attaching to the front of the hoods. Such caps are readily available from various sources, including the eBay vendor I use. You can even ‘re-assign’ some of the supplied Fujifilm caps from one lens to another (e.g. use the 52mm cap from the XF18 or XF35 with a 39mm vented hood). The quick overview table at the end of this post lists the required cap sizes.

Some people may prefer to use the supplied Fujifilm cap by mounting it deeper inside the hood. Installation and removal however becomes cumbersome, takes time and requires proper care.
The vented hoods perfectly accept the original caps: they get to sit halfway into the hood, past the vents, so the space immediately in front of the lens is sealed off. I found that the wide hoods simply will not adequately hold the caps. With cylindrical hoods, the caps fit but do not stay firmly in place. In addition, inserting or removing the cap may scratch the grooved interior, potentially exposing bare metal and causing reflections. Therefore I prefer using front-mounted caps with both wide and standard or tele hoods.

Enough caveats: let’s have a closer look at my choices and findings for the various XF lenses.

Very wide primes – 14mm & 16mm

Only one viable choice here, the wide model, as a vented hood will cause vignetting in the corners of the frame. Required thread sizes are 58mm (XF14) and 67mm (XF16).

The lens+hood combo is shorter than with the Fujifilm shades, but wider at the front. That is not am issue with my (ThinkTank Retrospective) camera bags. The front lens element remains adequately protected. And the whole screams power!

Wide primes – 18mm & 23mm

Here I prefer the vented variants (thread sizes 52mm and 62mm respectively). The lenses now take on the look of their classic counterparts and the overall bulk is reduced, especially with the 23mm. Have a look at my preferred street shooter setup:

Standard primes – 27mm & 35mm

This time we get some choices. The XF27 looks great with a vented hood, but a standard cylindrical one will no doubt do as well (39mm thread). But in this case ANY hood will defy the compact pancake nature, so mine usually goes out ‘as is’: bare naked.

The XF35 then looks great with both the vented model and the standard design (52mm thread). The decision becomes a matter of taste (and mood): I find myself alternating…

Short tele primes – 56mm & 90mm

My preference goes towards the sleek look of a cylindrical hood. Both the standard and the tele sizes will do on either lens, so I decided to split my options. Kudos to Fujifilm for the common 62mm thread size!

Don’t you agree that the 56mm looks quite ‘sharp’ on the outside as well in this ‘dress’?

What about the 60mm macro?

Good question. My XF60 doesn’t venture outdoors a lot, I mainly use it for product and close-up shots in the studio, where the default lens hood does well. Furthermore, the lens is known not to like stray light. If you find the original Fujifilm hood too large, be aware that the Fujifilm bayonet shade for the XF35 fits equally well (above right).

A vented hood with 39mm thread is another option, without disturbing the autofocus operation (something the XF60 is notorious for). I am sure a standard cylindrical hood would work too, I just never got one of those in 39mm thread (yet).

The ‘convenience’ zooms – 18-55mm, 18-135mm & 55-200mm

It’s a bit of a stretch to strive for a classic look with zoom lenses, but al least the XF18-55 is compact enough to pass for a longer prime – as long as you drop the default petal shade. And although my primes see ‘action’ more often, I do use my lighter zooms in similar situations, where a screw-on lens hood will stay on solidly and provide better physical protection.

My choices went towards a vented hood for the XF18-55 and XF-18-135 (58mm and 67mm threads respectively), and for a tele cylindrical one on the XF55-200 (62mm thread). Again, the resulting combination is more compact than with the Fujifilm hoods.

The ‘serious’ zooms – XF10-24, XF16-55 & XF50-140

These excellent lenses come with a heft that in no way you can ‘camouflage’ as a prime…
Also, in my case, those are the optics I go to for ‘serious’, more deliberate, top quality work. So here I prefer to stick with the original Fujifilm lens hoods, that provide good shielding against stray light across the zoom range, and – when mounted in reverse – take up little extra space in the bag.

Anyway, I doubt that the XF10-24 would stay free of corner vignetting even with a wide model hood, looking at the minimum depth of the original shade. So I did not even order an alternative in 72mm thread (yet). Same for the XF16-55, where in addition a wide hood would considerably add to the already significant 77mm front diameter.

The only exception: the XF50-140. Here, a tele cylindrical hood (72mm thread) works just fine and – as with the 56 and 90 siblings – delivers that sleek and slim appearance.

Time for a little recap

Here’s a quick overview of the models and sizes I am using with each of the XF lenses:

I have added the appropriate sizes for pinch style lens caps should you want to add these on top of the hoods, for extra (dust) protection.

Had enough of it? You bet!

Hey, guys and girls, don’t take all of this too serious! It’s only lenses and hoods, after all… Looks and style may be pleasant and fuel good discussion (preferably around a table, after a shoot!), but none of that pimping will improve your skills or get you better images.

So, take away from the above whatever you like, and keep up the good photo fun!

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Metabones Nikon F to Fuji X adapters – UPDATE

Two years later: where do we stand?

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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.

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Metabones Nikon F to Fuji X adapters – Conclusions

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

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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.

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Metabones Nikon F to Fuji X adapters – part VI

Image quality reporting continued

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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

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Metabones Nikon F to Fuji X adapters – part V

Playing like the big boys…

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TEST TWO: image sharpness – the hard way

“Natural” scenes, like the one in our first test, do not always have very sharp edges or high-contrast areas. That is why professional testers use dedicated high-resolution test targets, such as the widespread ISO 12233 chart.

I do not have a full-size “original” for this target, but some wed searching led me to a 18688x1168 pixel file: good enough to make an A4-sized print on photo paper (with my modest HP Photosmart office printer). Obviously a target of this size, resolution and quality will not allow to capture a lens’ true performance “by the numbers”, but it might do a reasonable job when comparing images shot with the Speed Booster, with a regular F- or G-adapter, or with a D700.

The (too) small size of my ISO 12233 copy forced me to at very short subject distances, with a narrow DOF, with hard to control parallelism between sensor and target, and suffering from the not-so-flat flat field reproduction by many lenses. Most lenses (unless designed for repro or macro photography) furthermore will not reach their optimal performance at nearby shooting distances.
So I limited myself to comparing two local areas, one in the center and one closer to the bottom left corner, as indicated on the target image. I also opted to shoot each lens at one f-stop down from fully open, to reduce some of the effects mentioned.

For this test as well the camera was repositioned when changing lens and adapter configurations to keep a more or less equal subject area covered.

 

Testing the Nikon AF-D 50mm f/1.4

Not too bad… we surprisingly see an improved performance with Speed Booster also in the corner.

Testing the Nikon AF-S 50mm f/1.4G

Same finding here: about equal in the center, improvement in the corner.

Testing the Nikon AF 50mm f/1.8

I also compared with the image quality when using this lens on a D700:

Testing the Nikon AF-D 85mm f/1.8

Testing the Tamron 90mm f/2.8 SP Di Macro

I was curious to try my favorite macro lens: I know it has excellent sharpness across the frame at close distances, but it also has a very flat field reproduction. And that shows in these samples:

 NEXT: More and different image quality tests

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