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Quote Originally Posted by Gustaftoni
Sometimes I get front focused pictures, even in full daylight, portraying a standing still person wearing colorful clothes. Those should be the best conditions for the AF, right?

Should be good conditions for AF, yes. Have you performed AF testing and if needed, AF Microadjustment. That's one great feature of the 7D - the ability to calibrate the AF of each lens. See Roger's article,[url="http://www.lensrentals.com/news/2008.12.22/this-lens-is-soft-and-other-myths]"This[/url][i][url="http://www.lensrentals.com/news/2008.12.22/this-lens-is-soft-and-other-myths]lens is soft[/url][/i][url="http://www.lensrentals.com/news/2008.12.22/this-lens-is-soft-and-other-myths]" and[/url][i][url="http://www.lensrentals.com/news/2008.12.22/this-lens-is-soft-and-other-myths]other myths.[/url][/i][i][/i]


[quote=Gustaftoni]That lens lacks detail. [/quote]
<div>Well, the optical quality of the EF-S 18-135mm is not stellar. It's a consumer-level zoom lens, meaning the optics are mediocre. The above AF issue may be a part of the problem - a slightly OOF image lacks sharpness. But you've got a mediocre lens, too.</div>
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<div>[quote=Gustaftoni]I need to be able to shoot in low light[/quote]</div>


Then you need a faster lens (i.e. wider maximum aperture). The EF-S 18-135mm has a variable aperture - the longer the focal length, the narrower the max aperture. The constant f/2.8 of the EF-S 17-55mm is a big advantage.


If you really want to shoot by candlelight or a campfire (without flash), even f/2.8 is not enough. Consider a fast prime, e.g. the 50mm f/1.4. I can shoot by candlelight alone with my 7D andEF 85mm f/1.2<span style="color: red;"]LII, and the 50mm f/1.4 is nearly as fast (and much, much cheaper).


Quote Originally Posted by Gustaftoni


Bottom line: which lens would you pick in my place? And which diffusor?


IMO, theEF-S 17-55mm f/2.8 IS USM is the best general purpose zoom lens for a 1.6x crop body like the 7D. Paired with a faster prime like the EF 85mm f/1.8 for portraits, you'll have a great combo.


You can get nice flash results with a 430EX II or 580EX II and a Sto-Fen OmniBounce, angled up to bounce off the ceiling.