Well .... the pixel density on the 5D Mk II is actually lower than on the OP's 40D. So the new body wouldn't be taxing the lens as far as central sharpness is concerned.Don't skimp on the glass when you have 20mp+ to feed. Go for the Canon.
thing is i could probably afford a 5d2 at the moment but another £700 on glass is out of the question. you would think that someone might have filled this rather large gap in the market
The 5D will recognise a Canon lens, and can make allowances, especially in the corners. Using a non Canon lens will give you lower quality pictures. Peripheral Illumination Correction is the full name. Why settle for lower quality when using full frame?
With such strong sentiments, i wonder if Sigma 24-70 actually sells!!
thing is i could probably afford a 5d2 at the moment but another £700 on glass is out of the question. you would think that someone might have filled this rather large gap in the market
Tamron do a 28-75mm f2.8 that seems to have its fans.
No its crop only for that lens. If Tamron lens is designated Di then its designed for crop sensors.
If your going to do some portraits you could grab the 85mm F1.8, its a cracking lens, a good focal length for portraits on FF and an EF lens so will work fine with it, can be picked up for about 1/2 the price of the L and is sharp as a tack.
I use mine on a crop, but its one I wont part with should I go FF.
No its crop only for that lens. If Tamron lens is designated Di then its designed for crop sensors.