« on: April 03, 2013, 08:00:42 PM »
Have people noticed alot of variation with Canon lenses?
Take a look at the tests done at lensrentals, where they test umpteen copies of the same lens; there's considerable variation from copy to copy across brands. In many cases it won't be obvious and may not even be noticeable, but sometimes it is. The second copy of the 70-300L I bought was clearly better than the first, while both 70-200 f/2.8 IIs I bought suffered from soft lower-right corners, albeit to different degrees (with the second one I probably wouldn't have noticed had I not looked for it, but I did... and am currently without a copy of that particular lens). Judging by the comments we see here, the 24-105 seems particularly prone to variation (I seem to have been lucky with mine). If my other lenses are not as good as they should be, it's to a degree I'm not noticing.
Bodies vary too, in all sorts of ways - for instance, my first Pentax K-5 was part of a production batch with stained sensors, my first 5DII and Olympus OM-D had dirt on their sensors, while the AF on my very first dslr, a Nikon D3100, broke after four months (am I particularly unlucky?). I understand that on some bodies the sensor isn't aligned quite properly; and so on. None of this is risk-free!