The reason why I originally started this thread is twofold. On one end, I was just curious to see and learn what your interpretation is of MTF charts, and fill in some blanks (such as how the MTF curves change when changing f/#). On the other hand, I was in fact timidly considering to get a prime normal lens.
I'll happen to be in NY at the end of September/early October, and I think that it would be nice to stop by BHPhotovideo downtown and take advantage of the currently very favorable exchange rate for us in the €-zone (assuming the money market does nor change dramatically in the short run). I said "timidly" because DSLR photography is just a hobby for me. I am really enjoying it, and while no piece of gear is "needed", many of them are just "wanted".

So, why a prime "normal" lens?
Well, I'd love a really low f/# just because of the creative oportunities that it offers, both in terms of narrow DoF, and in terms of low light shooting. So, wanting to consider a fixed focal length lens, I am thinking that a "normal" one is probably the best choice. But, is it? I am sure this is quite debatable, also considering that currently I own a APS-C-sensor body, and very subjective as well. On my APS-C body, a 35mm would do just as well I supppose. So, I've been looking at a slightly borader range of focal lenghts in the 1.2-1.4 range, and so far it seems to me that there are two main groups of lenses, in terms of price.

Less expensive group:
Canon 50mm f/1.4
Canon 50mm f/1.8
Sigma 50mm f/1.4



The only reason why I included the 1.8 is that, in fact, it seems to perform quite well for its price, not far from the Canon 1.4. However, Sigma seems to outperform Canon here, especially at low f/#, which in the end is what I am more interested in.
This is of course the group which would possibly make more sense for me, at present.


More expensive group:
Canon 24mm 1.4L
Canon 35mm 1.4L
Canon 50mm 1.2L
Carl Zeiss 50mm 1.4


The reason why I included the 24mm is that it seems to be wonderfully sharp, and it's there mostly as a reference point. Also, Carl Zeiss lens is MF only, so I am not sure it would make sense. What I find interesting is that the 35mm L lens is at 1.4 sharper than the 50mm . So, I wonder whether it would make sense to give up some image quality at 1.4 in favor of the possibility to shoot at 1.2 (rather than "only" 1.4).

Finally, these are expensive lenses. But, lenses are quite durable products, they keep their value over time, there is a good used lens market; moreover, a $1500 lens would actually cost me, now, as low as € 1000. This is so temptig that I could even decide to get an expensive one, provided it turns out to be attractive enough.

So, I just wanted to share with you my thinking. Any comment is welcome, as usual . Am I making sense or not at all? Am I forgetting some good piece of info, or lens in the market? Am I wasting my money?

P.S.: Oh, and lastly: I have been looking at lens resolution and image quality because I am assuming that distortion and color aberrations are to a certain extent fixable via lightroom or other software. But resolution and sharpness? Not so much, I am afraid. And, that's what I really like in a picture.