Ok well if you have only heard good things about the Canon 35mm f/1.4L, let me tell you a few bad things.
- Lens Rentals rents out over 700 different of lenses with over 12,000 individual lenses in their arsenal. The 35mm f/1.4L is responsible for around HALF of all inoperable focusing system failures they have, despite the rest of their inventory being several hundred times larger. Out of the 700 different lenses they have, the 35mm f/1.4 L has consistently been in the BOTTOM 20 or worse. That means that 680 lenses are more reliable than the 35mm f/1.4 L.
Like I said if you have problems with lenses having focus calibration, then you don't want a 35mm f/1.4L
Check the link if you have any skepticism:
"Canon 35mm f/1.4 14% Calibration, decentered element, autofocus failure"
The Canon 35mm f/1.4, not only cannot focus properly and requires calibration, but it's focusing system simply breaks, and many copies are severely decentered.
With that said 80% of copies of pretty much any lens are going to be good. What probably happened to you is that you bought multiple copies from a bad batch. I have purchased 3 copies of the Sigma 35mm f/1.4, to get the sharpest one and 2 copies of the Canon 35mm f/1.4 and haven't really had any issues with any of them, but what concerns me about the Canon is long term reliability. The lens simply breaks due to it's antiquated focusing system over time. You don't want to completely lose your investment.
If I were you I would just buy a Sigma 35mm f/1.4 from another source.
I don't want to go into a Canon vs Sigma argument, but here's the latest version of Roger's lens repair stats:
... drawing attention to a few points:
1. The main issue with the 35L is the AF/MF switch, which not many people need to use- it has instant manual override.
2. The rate of problems with the 35L has gone down.
The rate of problems with the 35L has only gone down a tiny bit, it's gone from being the 12th least reliable lens you can buy to the 15th least reliable lens you can buy, out of 700 other lenses. That is not good. I'm also not sure how it's possible to use full time manual overide to manual focus and do minor adjustments on a tripod, because the autofocus will completely refocus between shots in that mode...
3. The much revered 70-200 II has a significantly higher breakage rate. Does not mean people should stop buying them.
People should stop buying them if there is an alternative that doesn't constantly fail. People buy the the 70-200mm L II despite it's extreme breakage rate not because of it.
The OP wants a lens that isn't going to be defective and will be a safe investment. The Sigma with it's lower defect rate and lower calibration issues rate, lack of risk in being replaced soon, lack of risk of dropping dead, and 4 times longer warranty is a much safer bet.
I would just get a working Sigma 35mm if I were the OP.
Also, saying 35L is one of the least reliable lenses is probably overstretching the data. Again, quoting Roger Cicala:
"...from a pure resolution standpoint it has now been passed up by the Sigma 35mm f/1.4 lens, which is sharper both in the center and along the edges and corners. The Canon remains a bit more predictable, though, both in autofocus accuracy and bokeh"
From a pure accuracy standpoint the 35mm f/1.4 L will be more consistent. My Canon copies of the 35 1.4 had half the variation in focus accuracy of the Sigma 35 1.4, but we're talking about a difference of around 1/4 of an AFMA step so that's not really meaningful. I think what most people care about is whether a lens has severe focusing issues, ie severe defects not tiny little differences. The Sigma has fewer severe focusing defects related to calibration than the Canon. So the Canon has more defects but slightly less variation in good copies. The Sigma also does have slightly more nervous bokeh, but it also has stunning clarity and I think that images just look noticeably better when you average those two issues out.