bennyng
Benny Ng
I used to have an S-mount Heliar 50/3.5 (the ugly duckling non-collapsible version). I found it to be very sharp from f3.5 (splitting hairs but it was very marginally sharper than the Millennium 50/1.4 at f3.5). It's a good little lens but I found the lack of click stops on the aperture ring annoying (aperture setting easily slips) and the f3.5 max. aperture too slow for my use. I sold it in the classifieds here for $250.
Interesting. I did not realise the S mount version does not have click stops. The LTM version has click stops. But the single helicoid construction meant that the aperture ring rotated when you focus. At least they have aperture markings on opposite end of of the aperture ring to make things easier.
Anyway, here's 2 pictures for comparison. One at f/3.5, the other at f/8.0. Warning: FULL RESOLLUTION PICTURES when you click through.

Picture A

Picture B
All pictures are unadjusted and unsharpened JPEG image straight out of the Epson R-D1s on standard setting. ISO at 200.
It's really difficult to tell which is f/3.5, which is f/8.0. Usually the f/3.5 picture will be weaker in performance, but in this case, you really can't tell the difference.
For the answer to which is f/3.5, and which is f/8, click here.
Cheers,