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Quote Originally Posted by EPT1955
My problem is I cannot find anything anywhere which gives a clear and concise explanation of the difference between EF, EF-S and L levels. L apparently stands for Canon's professional line, but what about the other two - are they compatible with the 7d? Are they appropriate or or are some features useless on a 7d?

EF = electro-focus. Almost all Canon lenses do this (the exceptions are the tilt-shift series and the ultra-macro MP-E 65mm lens). EF lenses work on all current Canon dSLR cameras (and also on Canon EOS film cameras).


EF-S =electro-focus with short back focus. These lenses work only on Canon dSLRs with 1.6x crop sensors - that includes the 7D, the xxD line e.g. 50D, and the Rebel series. EF-S lenses do not work on 1-series (FF or 1.3x crop) or 5D/5DII FF bodies. With a couple of exceptions (e.g. 17-55mm f/2.8), EF-S lenses are low-to mid-level consumer lenses (i.e. not the best quality). The EF-S image circle is covers only the 1.6x sensor, meaning these lenses are cheaper (less glass).


The L-series is Canon's professional line - the red ring around the barrel indicates the best image quality and build quality. Many (but not all) L-series lenses are weather-sealed (note that L lenses other than the supertelephotos require a filter for full sealing - so, the 70-200mm needs a filter to be sealed). All L-series lenses are EF lenses, meaning they work on any EOS camera. Since they are designed for a FF image circle, when used on a crop body you get some benefit - even with L lenses, there are distortion/vignetting issues, and those are most evident in the corners which are 'cropped' out on a smaller sensor.


Quote Originally Posted by EPT1955
I am going to purchase two lenses. The first is the EF 70-200mm f/2.8L IS II USM (I wish the reviews and F/stop were better for 70-300mm or the 100-400mm).

The EF 70-200mm f/2.8L IS II USM is an excellent lens! It hold up well to a 1.4x teleconverter, giving you a 98-280mm f/4 lens that maintains weather-sealing (and the constant aperture is better than the variable aperture of the 70-300mm). For more reach, I usually use my 100-400mm when it's bright and dry, but at twilight or in the rain, it's the 70-200 II with or without the 1.4x extender.


Quote Originally Posted by EPT1955
I cannot begin to settle on a shorter focal length zoom (24 to 70mm or around that) for studio table top, and close people candid portraits (political events).My specifications are I want my short focal length zoom lense to have F/2.8, have Image Stabilization (IS) and have weather resistant construction for inclement weather.

That's a tough call - the lens you specify really doesn't exist in the Canon lineup (although if you believe the rumor sites, a 24-70mm f/2.8 IS lens is coming soon - but then again, it's been 'coming soon' for years).


IMO, the EF-S 17-55mm f/2.8 IS is the best general purpose zoom on a crop body like the 7D. Although it is a little short of L-series build quality, the optical performance is equivalent to L-series lenses. I use mine a lot, indoors and often outdoors as well. But, it's not weather-sealed. When it's raining, I use the 24-105mm f/4L, trading a stop of aperture for weather-sealing while keeping IS.


Good luck with your decisions!