Canon 17-55 f/2.8 or Canon 24-70 L f/2.8 to replace Tamron 17-50 f/2.8

Keith Z Leonard wrote:

 

Canon 17-55 f2.8 IS is a great lens, as is the Sigma 17-50 f2.8 OS, VERY sharp and both are much cheaper than the 24-70 f2.8 plus have stabilizers.  The aps-c vs 35mm format issue is that the crop sensor only uses a portion of the projected image circle, so there is a 1.6x field of view to take into account.  Usually people talk about these things in terms of 35mm equivalent.

So here's some math...

The 24-70 on the 60D will give you the field of view (FOV) of a 38.4-68.4mm lens on a 5D

The 17-55 on the 60D will give you the FOV of a 27.2-88mm lens on a 5D

So you can see that if 24-70 on 35mm is a "standard zoom" then the 17-55 on APS-C will give you roughly similar ranges.

In terms of image quality, all 3 of these lenses are likely to perform very well, I've used the Canon 17-55 and the Sigma 17-50 together, and there's not much between them.  Sigma is sharper in the center, the Canon in the corners wide open, from f4 onwards it's a non-issue.  The build quality is where you are likely to notice the biggest difference.  The L will be the best build including weather seals, then the Sigma and the Canon 17-55 in last place, quite plastic and rather large.

Crop sensors with their higher pixel density are quite demanding on optics, I think you ask your question a little backwards, rather than wondering if the 60D will do the lens justice, will the lens perform well on the 60D??  The new 24-70 f2.8 II is very well regarded for a 35mm standard zoom. It's my opinion that any one of these lenses will give you excellent photographs, it's up to you how much money you want to spend.

btw, the 75-300 is probably Canon's worst lens, so once you get one of these lenses don't be surprised if you become somewhat disenchanted with that lens, it's nothing personal here, I had one too.  

It's interesting that you say that I should be thinking about how the lens will perform on the 60D, because I was very happy with my Tamron lens on my Digital Rebel, but it has been a little disappointing on the 60D.  But I wonder if that is because I am expecting so much more since I did upgrade the body!

In your opinion, will I improve the image quality I get by replacing the Tamron with either the Sigma or Canon?  Or am I better suited to just upgrade my 75-300 lens?

I will admit that the Tamron lens is a bit slow with the autofocus...