The MD 2x Tele Converter 300-S is a pretty common Minolta tele converter for lenses with focal lengths of up to 300 mm. It is the shorter cousin of the 2x Tele Converter 300-L which is also known as 2x Converter for APO Tele Rokkor.
The converter itself weighs about as much as the 50 mm MD f/1.4. Combined with a slightly heavier prime like the MC Rokkor-PG 50 mm f/1.4, it becomes a little top-heavy on the NEX. The mechanics are top notch, though. My copy has a very tight fit on the camera as well as on the lens and the spring loaded aperture transmission lever works smooth and rapid. The spring also slightly dampens the aperture control ring of the lens. When using the converter, you are doubling the focal length of the lens while keeping the aperture opening constant, which effectively doubles all f-numbers (-2 EV).
For further details on the converter like weight and dimensions, have a look at its entry in the Minolta SR mount lens database. You should also be aware that the converter cannot be combined with every Minolta lens. Have a look at the MD 300-S & 300-L compatibility table to see, which lenses are supported and what restrictions might apply.
Condition of my copy
Optics: Excellent. No visible scratches, no dust.
Mechanics: Excellent. Smooth and snappy aperture transmission lever.
Exterior: Very good. Minimal scratches in the finishing here and there, otherwise like new.
Optical performance on NEX-5N / 5T
Notice: The quality of images taken with a tele converter is limited by the converter as well as by the lens it is attached to. The following review is therefore only valid for the combination of the MD 2x Tele Converter 300-S with the MC Rokkor-PG 50 mm f/1.4. Judging the quality of the converter is best made by comparing the shots of the lens with and without it.
The combination surprises at f/1.4 (effective f/2.8) with haze and low contrast but acceptable resolution in the center. The corners are very soft, heavily affected by the haze and show astigmatism – horizontal lines are rendered sharper than vertical ones. The latter might be caused by a slight misalignment of the optical axis of converter and lens. Stopping down to f/2 clears up most of the haze and improves contrast in the central region, but does not give higher resolution. At f/2.8, the last bit of haze disappears, sharpness improves to good levels and the corners finally show an acceptable performance. Sharpness stays good at f/4 with consistent performance across the frame and the astigmatism is not visible anymore. Diffraction becomes apparent at f/5.6 (remember: effective f/11), slightly softens f/8 and mushes the image at f/11 and f/16.
A medium red and cyan glow is visible at f/1.4 and f/2. The glow transforms into clear but remarkably small CAs at f/2.8, which do not shrink when stopping down. Certainly worse than what the MC Rokkor-PG delivers on its own, but still a solid performance for the lens-converter combination.
Vignetting is about 1 stop at f/1.4, improves nicely at f/2 and is gone by f/2.8. This is slightly more than the MC Rokkor-PG without the converter. The images also exhibit a barrel distortion of -0.5%, which is identical to that of the bare lens. The T-stop at f/1.4 (effective f/2.8) is approximately T3.2 (-0.4 EV), which is not impressive but also not worse than the lens without the converter.
In conclusion, the MD 2x Tele Converter 300-S combined with a MC Rokkor-PG 50 mm f/1.4 delivers usable results from f/2.8 onwards. Wide open and at f/2, the images show very soft corners and overall strong haze while offering acceptable central resolution. The converter seems to amplify the lenses weaknesses. The sweet spot of the combination lies at f/4, where image quality is good across the whole frame and detail – while lower than what the MC Rokkor-PG can deliver on its own – is certainly higher than a crop of an image without the converter.
The following images are pixel-level crops from the test chart. They may appear scaled in your browser window. Click on them to view the crops in full size and cycle through them easily. For more info on the test setup, visit the details page.
(Cropped areas marked in orange)
f/1.4 (effective f/2.8)
f/2.0 (effective f/4.0)
f/2.8 (effective f/5.6)
f/4.0 (effective f/8)
f/5.6 (effective f/11)
f/8.0 (effective f/16)
f/11 (effective f/22)
f/16 (effective f/32)