I finally received my Zuiko MC-20 teleconverter and was eager to run it through a few tests to see if it exacts an image quality penalty – as it theoretically must. Since the focal length rises, all of the optical aberrations in the base lens become exaggerated and more visible.
I was not able to test the Zuiko 300 mm f/4 PRO because even at 300mm focal length I cannot fully frame my new larger ISO 11223 test chart and remain inside my house. So I only tested the Zuiko 40-150mm f/2.8 PRO with the MC-14 and the MC-20 at a final 150 mm focal length as well as one other constant aperture, internal zooming lens for comparison – the Sigma 80-300mm f/2.8 in EOS mount but adapted to m43.
I also performed the resolution test that I introduced on the last blog to evaluate the resolution gains of High Res mode.
The resolution test unfortunately only tests an area right next to the image center and as the MTF curves show, the center in all tests is quite sharp so the numbers are all similar.
The falloff in sharpness does not occur until the peripheral 10% of the image for the base Zuiko 40-150mm f/2.8 lens and this falloff occurs sooner and closer to the center with the use of an increasingly powerful teleconverter. The Sigma 80-300mm f/2.8 performs nearly as well as the Zuiko but is a much larger and heavier lens.
So the MC-20 doesn’t break the laws of optics and it appears to be a quality product but you will lose two stops of light. It is a product of immense convenience but if you are able to carry lots of lenses and you need low light top quality images I would use my Sigma 500mm f/4 prime reduced to 350mm f/2.8 with a Metabones Ultra telecompressor. It will definitely outperform a Zuiko 40-150mm f/2.8 Pro with MC-20 operating as a 300mm f/5.6.