I can't speak for photozone, but I can say that the results I presented were accurate for the two lenses I tested. There's always a possibility that any sample of any lens is either better or worse than an average sample. That's the problem with lens tests. As far as I know nobody ever tests 10 samples and presents the results of each one or even an average over the set. In fact it's very rare that even two samples are tested.

On the few occasions I've had two samples of a lens to look at, they've always been pretty close, but they've always been slightly different. There are sample to sample variations, but normally I'm assuming that they are small enough not to be significant.

I take lots and lots of shots when I'm testing lenses. Probably more than 100 and my general conclusions are based on the results of looking at all the images, not just the one or two examples I present. I would never base anything on a single shot or just two comparison shots. Uusually if I say that "A" is better than "B" under some set of conditions it means that I've reached that conclusion by looking at shots of resolution targets as well as real world images.

One point to be aware of is that shots of resolution test charts are normally done with a pretty close focusing distance. If the chart is 2ft x 3ft for example, a full frame shot with a 50mm lens would be taken at a distance of about 1.2m (4ft). Most of my real world shots are taken at much greater distances from the subject - conditions more representative of normal use. It's possible that lens characteristics may differ at different distances. If I notice a difference I'd comment on it (normally I don't see anything too significant in that regard). It's also more likely that real world outdoor shots will be affected by flare than controlled indoor studio shots.

As for focusing, I normally test using both AF and using manual focus with Live View and 10x magnification. If there's a difference I'll comment on it (as I will in an upcoming test but I don't want to give details now until I've carefully checked my results).

So I can't explain differences in lens test results other than sample to sample variations or some flaw (or at least some difference) in testing methodology. I'm pretty sure my results are good but I can't really comment on anyone else's data because I've no idea how it was obtained.

I would not be in the slightest bit surprised of the EF 50/2.5 was the sharpest of all Canon's 50mm lenses at its optimum aperture. It's designed to be very sharp with a very flat field, as all macro lenses are.

If you want a 50mm lens that's as sharp as possible but no faster than f2.5, then it would be the one to get. However to say it's the "best" depends on what your use is. If your use is for low light work and/or portraits with a shallow depth of field, then of course it's the worst of all the 50mm lenses!

(As a secondary note: www.slrgear.com has actually done some MULTI-SAMPLE reviews with very interesting results. Here is the one for the  Canon 50mm ƒ/1.4 USM. It can be found here: http://www.slrgear.com/articles/variation_canon50f14/canon50f14.htm ) Hope that helps as well.

Better late than never !

I don't know what the papers and charts & tests say...
The 50/1,2 is fantastic.
I had some difficulty realizing it with the first shots.
The dof is so small that shots get easily out of focus.
But the results are magical !
I absolutely adore it and couldn't do without it !

Even if overpriced, still worth every penny !
10 out of 10.
Can post results if anybody wants...
George