An other 'What lens should I get thread' ....

Different lenses for different uses?

The 15-85 is a great general purpose lens It is not an artistic, large aperture for separation and bokeh lens. The Sigma 17-70 is probably a little better, but what you're describing is the realm of two or more lenses. The 17-5X lenses will work well as large aperture lenses, but lack the reach of the 15-85. Primes will give you large apertures, but lack the versatility of the 15-85.

I actually really love the 15-85, but I use it as a walk around lens and I'm not trying to get great bokeh or background separation you're describing. That's why I have a 30mm Sigma, or a 60mm Canon EF-S macro.

Would recommend the Canon 24-70 f2.8 II for one time expense. Taking into account going full frame in the future.

I've got a Tamron 17-50 f2.8 and my mother has a canon 15-85, I would say the 15-85 is a far superior lens and from what I've read the tamron is a much better opption value wise over the canon 17-55 f2.8 at under half the price.
F2.8 is nice but I often step to f4 to get sharper images anywho, crank the iso up a bit and all is good.

I had the same dilema as the O.P. So, in addition to my 15-85 I bought the 17-55. Problem solved right? Nope, I always use the 15-85 and never use the 17-55.

Thanks for all your assessment. This seems to be a doozie!

I do have a nifty fifty in my arsenal and if I put that on then I am quite satisfied with the portraits. But I don't know how anybody can possibly act fast with a 'fixy' in a party - space is very often limited.

I might just need to learn to switch lenses fast?

BigSky wrote in post #14663436
I always use the 15-85 and never use the 17-55.

Funny I found the reverse when I had both. I prefer the separation of the subject from the background at larger apertures, even when outside in good light. For landscapes, if the 17-55 is not wide enough I pull out my 10-22mm...

drmaxx wrote in post #14668270
Thanks for all your assessment. This seems to be a doozie!

I do have a nifty fifty in my arsenal and if I put that on then I am quite satisfied with the portraits. But I don't know how anybody can possibly act fast with a 'fixy' in a party - space is very often limited.

I might just need to learn to switch lenses fast?

get the 24-70 f2.8 II

belias1989 wrote in post #14668474
get the 24-70 f2.8 II

I definitely check into this lens. Any clear recommendation between Sigma and Canon before I dig into the specs? Or: Is in your opinion worth to spend more then twice the money?

Here we go, a week later and I still not quite happy with any of the possible solutions. I narrowed it down to:
* Tamron 24-70mm f/2.8 (the sigma seems to have some QC issues?)
* Canon EF-S 17-55mm f/2.8 IS

Any thought on that?