I sold my chrome Canon '28/3.5, and I wish I had kept it.
Raid,
I lost my chrome Canon 28/3.5 in a trade and missed it. Recently found a rare black version that is about 1/4 inch longer but also lighter in weight. Still it is a tiny lens.
The black version has better ergonomics for focusing because of a nice wide focus ring. The optics are reported to be the same, but the front element is even more deeply recessed. I expect this deeper shrouding to lower flare.
I found the chrome 28/3.5 I owned to have that 50's retro look, meaning very sharp center sharpness with softer corners and some vignetting that gets tamed as one stops down. Also the contrast is low even when compared to a 35/2.8 Summaron or a 50 Rigid.
I compared a lot of shots comparing the 50 Rigid, 35 Summaron and my new black 28/3.5 Canon using my Monochrom, and I will say that it renders with a rather "soft" contrast when even compared with other single coated glass. I am not sure if this is due to focal length (28 Cron ASPH displays lower contrast than my 35 Lux ASPH Pre-FLE, and both wides display wider histgrams, meaning a broader range of tones than my 50 Lux ASPH).
I did not include in the comparison my 35/1.8 Nikkor in LTM because the Thoriated glass displays about a half stop of yellow filter built in due to nuclear hardening. The 35/1.8 Nikkor also has its own distinct rendering, and the Nikkor on the Monochrom is a magic lens BTW.
I really love the 28/3.5 highlights because of this organic airy detail, but there seems to be a sacrifice in shadow detail because of the low contrast rendering. When compared to my 28 Cron the Cron lacks this highlight detail but displays tremendous shadow detail, so the contrast is rendered at opposite ends between these two lenses..
The Canon creates rather spectacular detail in the highlights (adjusting shutter speed for the widest histogram without clipping the highlights); while the 28 Cron accentuates the shadows. Overall I say with the Canon its mostly mid-tones and spectacular highlights in rendering.
As far as sharpness goes at F5.6 it kinda compares with the 35/1.8 Nikkor, but the 35/2.8 Summaron and 50 Rigid I say are sharper.
Cal