Maybe you have been attracted by the thought of the far lighter bodies of micro 4/3 cameras or the amazing array of functions (superb video and precision focusing aids for example) they boast  but been deterred by the 2x crop factor from changing formats – or even adding a body via an adapter and using manual focus on your lenses. Metabones have produced a intriguing optical device – the Speedbooster XL 0.64 that lowers the crop factor substantially  (to 1.28) and also produces an increase in the speed of the lens you are using by 1 and 1/3 stops… interesting, then read on.

Mt Terminillo, Lazio, Italy, July 2016

Eugenia’s pansy (Viola eugeniae) occurs in huge numbers on high mountains in the Apennines. Here the Laowa 15mm f/4 behaves as a 19.2mm f/2.5 equivalent used with a Metabones Speedbooster and gives an obvious wider ‘feel’ that when used with a simple adapter when it behaves as a 22.5mm equivalent wide angle on APS-C format.  

Before I began using a Sony NEX 7 about three years ago, I had realised that there were certain advantages to using mirrorless cameras for my experiments with wide-angle macro imaging, macro and microscopy: I am still finding new ones.  Everything stemmed from the fact that, thanks to the absence of a mirror (a feature of all DSLR cameras), the distance between the lens flange on the front of the camera body and the sensor can be made much less, making lens corrections easier to deal with because of a diminished air space.  Thus, when you use so-called legacy lenses you have to use adapters that not only convert to the lens mount but also build in some distance (effectively an extension tube with different mounts at either end) because lenses meant for full frame (and other)  DSLR cameras have their rear element further away from the sensor to accommodate the presence of the mirror. This allows some interesting experimentation and great flexibility in the use of legacy lenses. Read More

I particularly like working with rectangular fisheye lenses for my wide-angle macro work because they exhibit better good close-focusing capability than normal ultra-wide lenses. I have extolled the virtues of  the Sigma 15 mm f/2.8  rectangular fisheye on many occasions when I was using it on APS-C format (with Nikon bodies and with a Sony NEX 7). Using a lens like this, designed for full frame, with formats smaller than that, permits the utilisation of the centre part of the image circle. The images then show remarkably little distortion – just a bit of curvature towards the edges:  sharpness is excellent as is contrast and the close focusing capability is remarkable. In fact,  this was the main lens that both Clay Bolt and I used when gathering images for our e-book: Wide-Angle Macro | The Essential Guide.

Of course, I can use also this lens with the micro 4/3 (MFT) format and a suitable adapter (Nikon to micro 4/3) but then it behaves as a 30 mm wide-angle compared with  22.5 mm forAPS-C, that is, unless you use the Metabones SpeedBooster. Then with the model I use it behaves as a 19.2mm lens with a maximum aperture 1 1/3 times wider than f/2.8…around f/1.8 – but more about that in the next post.

With a change of format to MFT, I wanted to go that bit wider…

Samyang 7.5 mm f/3 .5 rectangular fisheye

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