The "Lens Turbo" speed booster is a 0.72x focal reducer similar to the more expensive Metabones "Speed Booster," which was first released in an electronically-coupled Canon EF-to-NEX form. My camera history is deeply rooted in Pentax glass, and I was thrilled when I first heard of the "Lens Turbo" alternatives going on sale in China via eBay. Though the cost is still arguably a bit high for a lens adapter, at $199 it's significantly cheaper than the Metabones alternative. And the mount selection is much higher with the Lens Turbo options, currently offering Pentax K, Canon FD, Nikon F, and Minolta MD. Though there were only a handful of sample photos on the net demonstrating the quality of the unit, I decided to take a risk and order one. Though I can't offer much in the way of a scientific review, I can give some real-world examples and comparisons.

From left to right: Pentax-M 50mm f1.7 w/ Lens Turbo - Sony E-Mount 35mm f1.8 - Pentax-M 50mm f1.7 w/ "normal" adapter

The build quality on the unit is fantastic, and it actually adds a marginal amount of unexpected weight to the camera. It feels solid and heavy, and it's apparent that quality workmanship went into crafting the adapter. The front mount is a bit tight, though I haven't had too much trouble mounting/unmounting the Pentax glass (I'd rather have a tight mount than a loose one). The field-of-view is actually a bit narrower than I expected, when compared to the Sony 35mm f1.8 which I'm planning on replace with the 50mm/Turbo combo. However, I haven't done any scientific tests to figure out the exact resulting field-of-view. And it's worth noting that my Pentax-M 50mm f1.7 does produce a slightly narrower crop than the Sony E-Mount 50mm f1.8 when used with a "normal" adapter.

Left: Pentax-M 50mm f1.7 w/ Lens Turbo - Right: Pentax-M 50mm f1.7 w/ "normal" adapter

As you can see in the above photos, the Lens Turbo does seem to add a bit of light to the image (both of these images were shot in manual mode, everything kept at the same settings). There is also a hint of vignetting wide open, and the adapter seems to add a slight green tint to the image, as well as a hint of distortion. Both of the above images were shot wide open.

Above: Pentax-M 50mm f1.7 w/ Lens Turbo, shot at f8. Click on the image to view at full-size.

In the above image, you can see the performance of the Lens Turbo when stopped down. The sharpness near the center if the frame is fairly good, though it does soften up considerably near the far left and right edges of the frame. It's also interesting to note that, at least in my copy of the Lens Turbo, the Pentax-M 50mm f1.7 focuses at infinity DIRECTLY at the far stop of the infinity mark. Many "normal" adapters have imperfections in mounting distance that allow you to sometimes focus slightly past infinity, and I might have just lucked out with this particular copy of the lens and adapter.

Now for some real-world examples. Most of the photos below were shot wide open, and had levels adjusted in post, including sharpness levels. These shots were taken to test out how I'd be using the lens turbo on a day to day basis.

Conclusions:

While the Lens Turbo isn't the perfect alternative to a full-frame mirrorless camera, it's a step in the right direction in terms of achieving that aesthetic look. The results, even wide open on older Pentax glass, are satisfactory enough for most circumstances, and I'd even feel comfortable using it on paid client projects under the right scenarios. It succeeds in widening the field of view to nearly the same as what you'd receive on a full-frame body, and it does seem to marginally increase the exposure as well. Yes, the edges do soften up a bit, and it does seem to smudge and swirl the bokeh a bit. But it creates a unique look, and opens up the option to use manual glass in either their original focal lengths (with the Lens Turbo), or at cropped focal lengths (with a "normal" adapter).

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Captured on film, Olympus Stylus Infinity.

Captured on film, Olympus Stylus Infinity.

Captured with a Sony NEX-6 and Sony 50mm f1.8 OSS lens as a stitched panorama.

On my flight up to Portland, Oregon last month, right as the sun began to dip low in the sky, I captured a series of photos around Central/Northern California. I wasn't exactly sure where, but my rough guess at the time was somewhere in the Sierra Nevadas. I haven't had much of a chance to sit down and sort through my photos from the trip one-by-one (other than the selections I've previously posted), but as I glanced at the first few images last night, I noticed this large lake in one of the photos I had taken:

Apologies for the color shift--The setting sun cast the lower half of the frame in shadow, hence the intense difference in temperature.

I didn't think much of it at first, but then I noticed the dam in the lower center of the frame. Thinking this was odd given the context, I began to look closer, realizing that there's actually (what looks like) a visible waterfall feeding into the body of water as well. My mind began to think back to a tragic tale of man-made environmental disaster that I had heard a couple years back, in which a pristine valley inside of Yosemite National Park was flooded to make way for a reservoir which would serve the water needs of San Francisco. After only a few moments of searching, I found my answer.

The same view, as seen from Google Earth.

Hetch Hetchy Valley, situated high in the Sierras, was once a pristine glacial valley which shared many similarities with the more popular Yosemite Valley not far away. It featured tall waterfalls which fed into the Tuolumne river below, and plentiful groves and meadows along the valley floor. Sadly, in the early years of the twentieth century, proponents began calling for the damming of Hetch Hetchy Valley in order to harness the resulting reservoir as a water and electricity source. John Muir, in The Yosemite (1912), wrote a harsh critique of those who proposed damming the valley in the name of human progress. According to Muir,

The proponents of the dam scheme bring forward a lot of bad arguments to prove that the only righteous thing to do with the people’s parks is to destroy them bit by bit as they are able. Their arguments are curiously like those of the devil, devised for the destruction of the first garden—so much of the very best Eden fruit going to waste; so much of the best Tuolumne water and Tuolumne scenery going to waste. Few of their statements are even partly true, and all are misleading.

[...]These temple destroyers, devotees of ravaging commercialism, seem to have a perfect contempt for Nature, and, instead of lifting their eyes to the God of the mountains, lift them to the Almighty Dollar.

Dam Hetch Hetchy! As well dam for water-tanks the people’s cathedrals and churches, for no holier temple has ever been consecrated by the heart of man.

The photograph above (circa 1908, Wikipedia source) is one of the few known photographs of the valley prior to the flooding. Judging from what little documentation we have, the valley prior to its final damming in 1923 was a remarkable and beautiful slice of nature, one that should have been protected were it not for an act of congress that authorized its destruction. I'm inclined to agree with Muir, who also stated in The Yosemite that "Everybody needs beauty as well as bread, places to play in and pray in, where Nature may heal and cheer and give strength to body and soul alike." Though it may have been a complete coincidence for me to capture an image of this once-great valley out of the window of an aircraft, it certainly serves as a reminder of the damage that man is capable of inflicting on the natural world, all in the name of progress.

Gear used on this trip: Sony NEX-6, Sony NEX-5n, Sony 35mm f1.8 OSS, Sony 50mm f1.8 OSS, Rokinon 85mm f1.4, Rokinon 8mm f2.8, Sony LA-EA2, Sigma 70-300mm f4-5.6 OS, Sigma 17-50mm f2.8 OS HSM, Sirui T-005 Tripod.

Gear used on this trip: Sony NEX-6, Sony NEX-5n, Sony 35mm f1.8 OSS, Sony 50mm f1.8 OSS, Rokinon 85mm f1.4, Rokinon 8mm f2.8, Sony LA-EA2, Sigma 70-300mm f4-5.6 OS, Sigma 17-50mm f2.8 OS HSM, Sirui T-005 Tripod.

Gear used on this trip: Sony NEX-6, Sony NEX-5n, Sony 35mm f1.8 OSS, Sony 50mm f1.8 OSS, Rokinon 85mm f1.4, Rokinon 8mm f2.8, Sony LA-EA2, Sigma 70-300mm f4-5.6 OS, Sigma 17-50mm f2.8 OS HSM, Sirui T-005 Tripod.