I do own them, use them and understand their real worth, only I have not used them at middle apertures and middle distances, hence the question. One frequently hears discussion of their brilliance at close range, and at distance stopped down, but rarely for the bit 'in between.' For landscape work, they are remarkable and you can add about 80mm of IC to the 210mm at F32 to start with (compared to published specs). I also own a 300 f9 Geronar and wondered, if like that lens, small apertures are necessary for good performance, regardless of distance. I know the Geronar is a triplet, but wondered if the small aperture requirement on the G Clarons was required to get over the correction for macro focus range they were presumably originally designed for. What I am hearing here suggests stopping down is partly about coverage and also partly about optimised distance, although the both are likely to be less of an issue with my intended project application. It may turn out that they perform as well as a regular f5.6 plasmat at these distances, or possibly not. I guess I will find out.