Has anyone done this to see in what ways the new ZE 21 is better than the CY from the perspective of IQ - CA, distortion etc. CY is plenty sharp already.

thanks.

Zeiss talk about improved resitance to CA and flare. My experience with a ZE lends credence to this, but I never used a C/Y 21 for comparison. It is fair to say that my 3 C/Y lenses (25, 135, 180) are much more prone to these issues than my ZE 21 but that is only an indication at best, not a fair and scientific comparison.

Zeiss talk about improved resitance to CA??

I haven't noticed any CA on C/Y version so far ..

They don't say "compared to C/Y", they just say "improved"...

When I look at some of the pictures with the new ZE 21 presented here in the forum, I would say that the new ZE has a much better resistance against flare than my original CY 21.

I can only comment about the ZF21 not ZE21, but by all accounts the ZF and ZE use exactly the same optics so hopefully this will help.

I have a ZF21 and a CY21, and in terms of overall IQ they are about as good as each other IMO. There are slight differences between them, as described in these threads among others -

http://www.fredmiranda.com/forum/topic/766524/0#7029256
http://www.fredmiranda.com/forum/topic/768584/1#7039716

Leaving ease-of-use aside (ZE on a Canon body should win that one), whether one or the other is really 'better' in any area comes down to personal preference.

Digloyd had a review I read when the ZF came out. Apparently, the composition of the glass has a different formula than the CY version (probably due to lead and other heavy metal regulations, RoHS, etc). Depending on what he was shooting, he sometimes noticed a strange, barely noticeable, cyan cast that covered what we refer to as the "Zone C" area.

Good point - with the ZF21 there is a cyan cast in the corners of the frame. The same can be seen in the ZE21 samples posted elsewhere on this board. The CY21 doesn't have this problem.