My 70-200mm is the Sigma EX DG f2.8 - it is fantastic.  I would leave it at that but such an evaluation might not be what you are looking for.

Thing is "outdoor work" - if you are refering to getting a building completely in your shot or a tree you have to be standing about 50 metres away from it at 70mm on a 1.6x crop.  The 70-200mm is a telephoto lens...meaning any sort of close work is pretty much a "macro-style" shot. It focuses down to 100cm which is pretty good and useful.

Anyway - apart from those constraints of the focal length, the thing is one of my favourite lenses - fast AF, nice bokeh, crisp image... alround corker of a lens - RRP is ~£750 if i remember rightly, but that is a bit cheaper than the Canon version and at that end of the spectrum (this thing is basically part of the sigma "pro" lens range) the differences are minimal and only really scrutinised by perfectionists.  Chances are that you might not want to spend so much on a lens... but getting the best shots out of the worst conditions means spending $$$'s sadly :-(

I'm not saying you shouldnt get something like the 17-85mm or the 28-105 - it might be exactly what you are looking for... just bear in mind that you might want to attach the lens to the camera before you purchase it and get a feel for the focal length (ie it's reach and its wide end capabilities.)

28mm is not wide on the 1.6x crop sensor, which is why cannon brought out the 17-85mm for the EF-S series of cameras: 17-85mm on the 1.6 crop is the equivalent of a 27-136mm lens on a full frame sensor - meaning that the 28-105mm you were thinking of getting is the (roughly) equivalent lens for a full frame.

Anyway - i'll say it again - check that site i posted for all the good lenses on offer... pay attention to what people say and rate for each lens and make a decision from there.  Here is a link to all of their reviews... check out tamron and sigma as well - they are reputable lens manufacturers for the canon mount.

"In every colour, there's the light.
In every stone sleeps a crystal.
Remember the Shaman, when he used to say:
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