canon 15-85 vs tamron 17-50 (non VC)

i currently own 15-85, its good daytime outdoor general purpose lens, but its max aperture is really low and i find myself taking canon 50mm f/1.4 at night (when i cant use a tripod) or when i want to take photos of people (or other subject requiring better dof)
i've been comparing resolution charts here at TDP and i dont see such a huge difference between 15-85 and tamron. distortion, ca and vignetting i dont consider a problem cause it can all be fixed in post so image quality, maximum aperture and flare resistance are most important to me

i'm considering selling 15-85m and buying 17-50 tamron and put the rest of the money into savings for some prime (maybe 100mm f/2.8 macro or 10mm f/2.8 sigma fisheye)
theres also possibility of selling 50mm f/1.4 which i find myself using about 10% of the time, but the thing is i really like it as a portrait lense and if i sold it and bought 17-50 tamron i'm afraid i'd spend most of my time using tamron and 15-85 would sit at home so it would turn out a bad decision...

buying canon 17-55mm f/2.8 is not an option, its currenty out of my price range
my dslr is canon 60d

pleas share your thoughts

edit: i just remembered something thats probably important, i'm mostly using 15-85 i 15-50mm range, so tamron would fit there, except that its widest angle is 17mm... i'm not certain how big of a deal that is

Only question is, if you sell the 15-85mm and buy the 17-50mm, you'll lose 15-17 and 50-85 from your range of focal lengths. You'll be surprised how useful that 2mm at the bottom is, and will you miss the 35mm at the top?

I was actually considering similar (but the 15-85mm for the canon 17-55mm) and decided the increase in aperture isn't worth the loss of range for me.

I just need to find another way of getting the low-light ability I need, on a useable indoor focal length (I find even 35mm too long indoors, our houses are small in the UK :D).

IF you get a good copy, the Tamron 17-50 f/2.8 non VC is excellent with IQ on par with the 15-85 and 17-55. I'm 1 for 2 with the lens. Buy from a reputable place with an easy return policy if you go that way.

Here are a couple shots with the 17-50.

http://riverview.smugmug.com/Naturea...99_epniA-M.jpg

http://riverview.smugmug.com/Naturea...04_w5Xec-M.jpg

I have a Tamron 17-50mm and missed the return window because it was still the 15 days at B&H. I sent it to Tamron 3 times and on the third time, it was as good as it gets. I have used it on an XTi, XSi, and now my 7D. I do find myself at the 50mm range quite a bit wishing for longer. These are the times that I use the Canon 24-70mm I love that lens and will only get rid of it when I go all time FF. It is a good performer and sharp as a tack!

I can also recommend the Tamron 17-50 non-VC. It is very sharp, also at 2.8, and I would definately buy one again if something happens with the one I have now (it fell on a stone floor but only got a crack in the hood, still tack sharp). Loads of lens pr. $$ (or €€ or Kr).

Lars

I'm actually in the same situation as the OP, but i'm leaning the other way.
On my 7D, I've got the EFs 15-85 for outdoors, hiking, anything in sun, and especially landscapes (more especially when I can only carry one lens).
For low-light i've got the Samyang 35/1.4, Pancake 40/2.8, 50/1.4, 50/1.8, FL 55/1.2, EF 85/1.8, EF 100/2.0. That may be a bit to carry around all at once, so I don't, I pick 2 or 3 for whatever event to which i'm going, maybe swap lenses a few times, sometimes don't even bother.

The f/2.8 zoom (in my opinion), is the does-most-things-ok-but-nothing-the-best compromise.
The 15-85 has the widest, the longest, the IS. The primes have the fast aperture.

So, the decision is between does-it-all in one lens if you can live with the shortcomings (and it's cheaper than a bucket-o-primes), vs what is essentially two kits that does what it does better than the compromise-zoom.
But in your case, given the price differences (depending on for what you can sell the 15-85), i'd keep the 50/1.4 and invest in a longer fast prime, 85/1.8, 100/2.0, 100/2.8 macro to make up some shortcomings in the length of 'only' 17-50.

I agree with Dr Croubie that 17-50 is a bit wide sometimes, so last year I supplemented it with a 85/1.8 to get better portraits. The gap between 50 and 85 is rarely missed, but I would miss the wide aperture of the 17-50 many times (I have a 400D, so the ISO noise is quite bad at 400 and up).

Lars

thx for comments, people

i found a little program called ExposurePlot. the program can scan all your photos and generate usage data that tells you which focal length, aperture, iso and shutter speed you use the most. i think its a great help if you're in a situation like this since it gave me facts about my usage, instead of just me guessing. if someone else needs the program, its free and can be downloaded here http://www.cpr.demon.nl/prog_plotf.html :)

17-50mm is 27-80 full frame equivalent so i checked how many photos i have outside of that range, it turned out i used 24-26mm 42,64% of the time (which is almost half of all my photos!) and that i used 80-130 range for 25,76% of my photos, again too huge amount to ignore... so that in short means that i use range that 17-50mm tamron doesnt have a whooping 68,4% of the time

but this didnt make the choice easy cause when i checked aperture i use the most i found out i'm using apertures slower then f/5.6 only 39,6% of the time (f/5.6 is the maximum aperture for 85mm on 15-85zoom and apertures of f/5.6 and wider is what i'm using in low light situations and for portraits, i use slower apertures, mostly f/8, for landscapes, daylight shooting and anytime i need to "keep everything in focus"). that means that i do need a faster aperture a lot of time

after reading all the comments here and some thought about information this program collected i decided that i cant sell my 15-85, its range is too useful, but i still need a faster universal lens that i could take in more light demanding situations. so i need both 15-85mm and f/2.8 and i'm going to save up a bit and buy tamron to use it alongside 15-85

@Dr Croubie
i dea of having a range of primes is very appealing, but also very expensive compared to the price of one general purpose that deals ok with lower light situations. it would take time to save up for setup you suggested and are using yourself, and it gaps would bother me a lot, especially on wide angle end. i have read about great Samyang 35mm and would definitely like to get one some day, but i feel this zoom is a priority right not :)

once again, thx for the help, people!

Your camera isn't full frame is it? Does that software convert for full frame?

If no for both of those then you shouldn't be either.

17-50mm is 17-50mm. You just only see the centre 0.625 of the frame. But that is the same for EVERY lens on your camera. So ignore it.

i have canon 60d and software does convert focal length to full frame equivalent