I have used the 300/4 with the mutar II on many occaissions. There is definitly a small softening effect, but it is still much sharper than my Yaschica 500mm mirror. There is a color shift too-tending towards blue. I have not yet tried a warming filter yet (81b or 812). Exposure can be a bit low, so consider overexposing by one stop. All in all, I am happy with the setup. Just wish I could afford the CZ 500/4.5-there was one on ebay two weeks ago.
Ron in NM
I have used the TT 300/4 with both Mutar II and Mutar III (400mmf5.6 and 600mmf8). The results are good with some loss of contrast and sharpness. It is not as sharp as my Mirotar 500mm/8 by its own. For the TT300/4, the average MTF value of the 10 lpmm curve shall drop from about 0.8 to approx 0.7-0.75 at max aperture, I guess, based on the published results of the apotessar 300/2.8 + mutar II combination.