Optical performance:
A converter can only be as good as the basic lens used, the selected aperture and the adjustment to the basic lens permit.
The E converter by Olympus for the FT system were very good and showed at best a little loss of brilliance and slight loss of sharpness in the border areas.
The MC-14 is significantly cheaper (it is indeed less glass and metal used).
The loss of brilliance here is somewhat stronger than the EC-14 and the loss of sharpness is at fully open aperture (f: 4.0) at 40-150 mm PRO not really low - stronger at the edge than in the center but it is visible. And that was in all 3 copies so miraculous and unlimited picture resolution you should not expect here.
Price-Performance
The price is mainly in the purchase of the 40-150 mm PRO (200 charges) really even fair. The single purchase is worth it not really.
Disadvantage:
Olympus is unfortunately moved away from the very practical way to offer converters suitable for all lenses.
Olympus converts now on Nikon paths and builds the MC 1.4x so that he previously only fits on the 2.8 / 40-150 mm PRO and the upcoming 4.0 / 300 mm PRO.
From the manufacturer's point of view this is understandable, because in WW converter lenses and low-light zoom make virtually no sense. A converter requires a fast lens with f: 2.8 or worst f: 4.0 to still be able to focus quickly and safely. (For DSLR Teles combinations with F: 5.6 lens with AF possible)
But Olympus forbids the converter with lenses like the f / 2.8 60mm Macro, the 1.8 / 25 mm, the 1.8 / 45 mm to use 1.8 / 75 mm where he definitely an exciting addition would.
I'm not particularly impressed by Olympus 2.8 / 40-150 mm PRO nor of this converter. Both are not bad but not very good.
Still, I'm glad that Olympus finally offers a converter, with a MC-20 would be more helpful and compatibility with all telephoto lenses would be very important to me.
Panasonic sleeps here unfortunately, despite several announcements so far not a single light-strong super-telephoto in sight and a converter anyway and although for me through her outstanding logical operation and ideal handling a GH4 or GH3 previously best mirrorless cameras for telephotography are.
For me the MFT system is a welcome addition, which I prefer at present clearly Sony, Fuji, Canon, Nikon, Samsung, Leica. However, I use MFT usually only up to 150 mm zoom focal length and possibly in the best light. Otherwise, light intensity, autofocus, resolution and handling of a Canon EOS 7DII are clearly at an advantage.
I forgive not as frequent 5 star because this is a theoretical maximum score for me, the most a few months or 1 year continuous use not often survives and I compare critically.
All the love due to critical experiences anfeinden me here, here are a few photos:
(See Oly 2.8 / 40-150 mm per report)