Quick decision help: canon 24 vs zeiss 21

[wayno]

The 24L ii is a great lens - superb for landscape stopped down but probably not as useful with the advent of the 24-70 ii which appears to match it. For me, where the 24 is simply unmatched is low light bokeh portraiture wide open. Something the Zeiss won't do as effectively. On that rationale, I prefer the L simply for the flexibility however if its purely landscapes the Zeiss is probably slightly ahead.

[Botts]

I would qualify Optikus's reply : manual focussing on an slr is much more difficult with wide angle lenses than with longer focal lenses. That's because things don't "snap in focus" in the same way, due to the wider dof. You may see things in focus on your viewscreen, which provides a small enlargment of your picture, but when printed at a significant size, you find out that your focus plane is not where you expected it to be.

Even if you've manual focused with an SLR before it may not be like MFing on a DSLR.  Keep in mind that MF only SLRs had good focusing screens that sacrificed brightness for accuracy.  Things like split prisms are extremely useful.

New SLRs don't have these focusing screens and thus it is extremely hard to nail manual focus.  You could always use liveview to MF in 5 or 10x, but this is slower.

Expect to upgrade the focusing screen (not easy) in your 5D3 to maximize MF lenses.

[NWPhil]

The Zeiss 21mm T* ze mount has the AF confirmation chip - so is just a matter of slower manual focusing.
Don't have the 24 II 1.4, but as others said, below 2 -2.8 most WA are soft - pretty much the same as you find on the 35mm, which I have too.
I rather have wider, and yes, although 3mm does not seem quite much, well, it is
Now, if you really want to have both focals, and can live with MF, then consider the 24mm TSE II....but will be slower than the other two options, and possible $$$$ depending if you buy new or used.

[wickidwombat]

I prefer the 20-21mm focal length over 24mm so for me the call is easy zeiss 21mm all the way
I have the 20mm voigtlander with AF confirm and electronic aperture control so using back button focus
the only real difference is my hand is the focus motor but it beeps and confirms focus quickly plus if i'm using my 5Dmk2 with brightscreen its very easy to see when MF is achieved. I've been thinking about getting the zeiss but i am happy witht he little voigtlander which is tiny like the 40mm so it goes everywhere with me where as the zeiss is much bigger and heavier so I dont think i'd take it along as often