Specs:

Lens:
300mm

Aperture:
f/5.6 to f/22
6 bladed aperure

Closest Focus:
6m (20ft)

Weight:
727g

Mount:
M42

Covers:
Standard 35mm film size (24×36 mm negative)

Image quality

Wide open:
Not crazy sharp but good enough
Some corner softness but still have a little even at smaller apertures (Fullframe)
Little vignetting

Renders very good at all apertures.

Build quality

Very good and with a nice solid and quality feel.


Conclusion

Nice lens with good image and build quality.
Wide open is not crazy sharp but more than enough I would say.

Can be a bit tricky to focus a f/5.6 lens on a SLR intended for manual focus.
The focus aid doesn't work at that aperture.
Not a problem you find on a Digital SLR especially if you use liveview.

Thumbs up:
Image and build quality
Bokeh


Thumbs down:
Closest Focus: 6m (20ft)




Technical Info
Scanner: Plustek OpticFilm 7600i
Film: Rollei RPX 100
Developer: Kodak D76