Hi to all,


I am new here, too... quite helpful forums. I use all those three lenses listed by Gustaftoni with my 7D very often. I am not sure but maybe my delayed comment still may help you.


EF 70-200 f/4 is great but I'd invest a few more bucks to get the newer version with IS, you won't regret that.


EF 50 f/1.4 is a superb lens for portrait, in paricular with a 1.6 crop cam like the 7D, it is great for video as it can be focused manually with good precision and is light enough for hand held video sequences. It's image quality is said to be not as good as the Sigma 50 mm/1.4 with open aperture but I am quite happy with it - the Canon lens is much lighter and more compact. If you stop it down to 5.6 and more it is tack sharp. I used it even sometimes for landscape photography.


EF-S 17-55 f/2.8... that's the only Canon lens in my collection that I both love and hate. Need to be careful as there are many fans of this lens out there. The pros are clear: versatile standard zoom range, very fast so you can get a nice background blur, very good IS so if you prefer available light photography you will appreciate that together with its fastness. Stopped down it is overall sharp but I really cannot see any more details when I use it with the 50D and with the 7D, so it cannot turn the 7D's sensor resolution fully in image details.


Quite an issue of the 17-55 is chromatic aberration - color fringes. In bright conditions sharp edges turn into sort of rainbows. Past year I had an extended e-mail correspondence with Bryan about this issue, I shot a test series with a Siemens star. Even stopped down to 5.6 it showed subtancial see color fringes at whereas my cheap 18-55 mm produced clean edges. Obviously Canon's engineers could not completely control CA in such a zoom ranging from wide angle to short tele, and using very big lenses (as a physicist I know that big lenses always produce a lot of CA and need an alaborated correction lens system). In practise you need to correct CA quite often during post processing (e.g. in DPP) if you shoot architecture, mountains or other objects with sharp edges in bright light - wheras landscapes or portrait works nicely.


Another issue is its famous dust problem. At least my lens collected such a layer of dust behind its front lens within one year that I'll send it better to Canon's service. Some dust specles do not affact image quality but from that much I expect to get closer to some visible effects (flares or at least loss of fastness).


So, overall, I'd recommend to think about EF 24-70 L as alternative and adding later a wide angle prime. That's more expensive, of cours, but the EF lens has the plus that you could use it later with a full frame body, too.