Hi Lorek,
What does EX, DG, IF and HSM stand for?
EX = Exclusiv, HighQuality, like 'L' (luxury) with Canon
DG = Digital Grade, coatings optimized for digital camera's. Note DG is still FullFrame! The EF-S equivalent of SIGMA is called DC.
IF = Innen-focussierung, internal focussing, so no turning outer lens elements (usefull if you use polarizing filters)
HSM = HyperSonicMotor, silent focussing, SIGMA's USM equivalent
(source:
http://www.sigma-foto.de/cms/front_c...ent=1&idcat=15,
or
http://www.sigma-photo.com/lenses/lenses.asp if you prefer English
)
If you can miss/spare the extra 4mm on the wide end, IMHO the Tamron 28-75 is a better lens than the Sigma 24-70.
The main difference between the Sigma 70-200 and the Canon 70-200 NON-IS is the buildquality (and colour rendition
)
I shot and compared the Sigma and the NON-IS 70-200 Canon, on my -then- 10D you could easily see the SIGMA had a slightly warmer tone compared to the Canon (a reddish/yellowish 'cast', not annoying, just different
).
In the end, I opted for the Canon 70-200
IS, as IMHO IS is a very very usefull extra, giving the lens more versatility.
The 70-200 IS is my second most used lens, the (Canon) 24-70 is my most used 'workhorse' (- at the moment - ).
Main difference between the Canon and SIGMA 24-70: again build quality and colourcast: in the case of the 24-70's I tested, the colour difference was a bit less pronounced than on the 70-200's I shot, but the difference in build quality was more evident between the 24-70's.
Hope this helps some, *my* €0.02 worth...
Kindest regards,
Max@Home