Metabones Devil's Speed Booster Q666 0.50x Press Release

Petersburg, VA, USA, Aug 30, 2017:  Caldwell Photographic Inc. and Metabones®  is pleased to announce the Speed Booster Q666, a.k.a. “The Devil’s Speed Booster”, exclusively for Pentax Q series cameras.  With its 0.5x magnification and world-record f/0.666 maximum speed it is crazy wicked fast.  So make a deal with the devil today and turn your Pentax Q with its back-illuminated sensor into a monster low-light machine unlike anything ever seen in photography.  Attach an f/1.2 lens and stop down a little to see how Stanley Kubrick made do with f/0.7 for filming those famous candle-lit scenes in “Barry Lyndon”.  Or open up all the way to f/0.666 and probe the darkness in a way that no photographer has ever been able to do until now.

With an advanced 6-element optical design, the Q666 packs lots of optical horsepower in a small package.  Sharpness is excellent even at f/0.666, and is downright superb if you stop down to f/1.0.  Distortion is very low, with a maximum value of, naturally, 0.666%.  And thanks to the back-illuminated sensor used in Pentax Q cameras, the full f/0.666 maximum aperture can be utilized with minimal pixel vignetting effects commonly seen in other cameras used with high-speed lenses.

Figures 2 through 4 below show MTF at 10, 20, and 40 lp/mm as a function of image height for output apertures of f/0.666, f/1.0, and f/2.01.   At f/0.666 (i.e., with an f/1.2 master lens) the MTF is high near the axis, and only falls off gradually toward the corners.  As the aperture is reduced to f/1.0 and then f/2.0 the MTF becomes very high and more even across the field.  Figure 5 shows that there is less than 1 stop of corner illumination falloff even at f/0.666.  And guess what - there is no vignetting at all after the output aperture reaches f/1.82.  Figure 6 shows that rectilinear distortion added by the Speed Booster Q666 is negligible at less than 0.666%.

Like all Metabones Speed Boosters, the Speed Booster Q666 is optimized to fully account for the camera’s filter stack located near the sensor surface.  This is especially critical at the record-setting f/0.666 aperture now possible with the Q666.  As a result, an enormous range of optics, from vintage film lenses to the latest digital designs, will function flawlessly when adapted to any Pentax Q camera.  Planned lens mounts for the Speed Booster Q666 include a Pentax-K version and a Nikon F/G version with the most advanced Nikon G aperture adjustment mechanism in the industry.

The Speed Booster Q666 will be available starting in Aug 2017 from the Metabones website ( and its worldwide dealer network for US $489.00, plus shipping and applicable taxes and duties. 




Figure 1:  Speed Booster Q666 design layout

Figure 2:  MTF at 10, 20, and 40 lp/mm for f/0.666

Figure 3:  MTF at 10, 20 and 40 lp/mm for f/1.0

Figure 4:  MTF at 10, 20, and 40 lp/mm for f/2.0

Figure 5:  Relative illumination

Figure 6:  Distortion




Metabones Nikon G to Pentax Q Speed Booster Q666 0.50x Product Pictures:








Metabones Nikon G to Pentax Q Speed Booster Q666 0.50x Specifications:

Model Code:  MB_SPNFG-Q-BM1

Color:  Black Satin exterior; Black Matte interior

Magnification:  0.50x

Crop Factor for Pentax Q, Q10:  2.8x

Crop Factor for Pentax Q7, Q-S1:  2.3x

Maximum Output Aperture:  f/0.666 (with f/1.2 lens attached)

Rectilinear Distortion:  < 0.666%

Lens Elements/Groups:  6/4

Length Reduction:  10.1 mm

Supported Cameras:  Pentax Q, Q10, Q7, Q-S1

Camera Mount:  Pentax Q-mount

Image Format:  7.44 mm x 5.58 mm (1/1.7”)

Lens Mounts:  Nikon F/G

Lens Compatibility:  Any full-frame (36 mm x 24 mm format) or DX format (APS-C) lens with the appropriate mount can be used.

Special Features:  Long-throw clickless aperture ring on Nikon F/G version

Dimensions: 27 x 76 x 72mm for Nikon F/G version

Weight: 193 grams for Nikon F/G version

Tripod Mount:  Robust removable type with Arca Swiss compatibility



  1. MTF data is a full diffraction-based calculation that assumes the Speed Booster Q666 is attached to a perfect master lens having an exit pupil distance of 100mm.  Note that the MTF calculations do not take into account sensor-induced apodization effects, sometimes called “pixel vignetting” or “pixel shading”, so actual results at large apertures are likely to be better than the calculations indicate.


  1. Illumination data assumes a perfect master lens with an exit pupil distance of 100mm and zero vignetting. Actual results will depend on the exit pupil distance and vignetting characteristics of the master lens used.


About Metabones

Metabones®, together with its allied partners Caldwell Photographic and WB Design, is the pioneer and leader of two key technologies which have catalyzed the transition from mirror to mirrorless. Speed Booster® (winner of the 2013 TIPA Best Photo Accessory Award) makes lenses brighter, wider and sharper, and Smart Adapter™ breaks the lens mount compatibility barrier by electronically integrating interchangeable single-lens reflex (SLR) lenses and mirrorless cameras. Metabones® offers a comprehensive range of adapters covering most popular lens mounts, as well as some rare and exotic ones. "Always at the forefront of innovation without ever setting aside practicality as a professional tool" perhaps best epitomizes Metabones' philosophy.