Cheap 50mm unreliable - what do I need instead?

excuse me jesper , this is no answer , rather a question to you as well as others.
i was contemplating buying this lens . so how long and how well did you use this lens before it started
giving you problems ?
is it worth buying at all despite the price ?

I'd recommend the Canon 50mm f/1.4 - same focal length, but higher build quality and slightly wider aperture.

Hi Manuj, Don't get me wrong, I would definately recommend this lens. It served me well for a couple of years and with the very low price, it should be part of the basic kit for most EOS photographers. Being able to spend a bit more now, I want to replace it with something even better, rather than just buying the same again.

Repairing it yourself: I'm just guessing here, but the answer is probably not. Although, given that it's not particularly usable at the moment and is not worth much, you don't have a lot to lose by taking it apart and trying to fix it yourself ...

As far as I know, none of the third-party lens manufacturers make fast 50s. They make 50 macro lenses, but those tend to be at least a stop slower than your 50/1.8. So if you want something at least as fast as the 50/1.8, you're looking at a Canon lens (unless you're OK with a manual-focus lens from some other system with an adapter). From cheapest to most expensive (and only considering current products):

• You already know the 50/1.8; lousy build quality, but dirt cheap and sharper than your zoom. If it dies, you toss it in the garbage (or sell it on eBay, clearly marked "as-is" with a description of the problem, to someone who wants to use it as a parts donor to fix their own broken 50/1.8) and buy a new one for well under USD100.
• The 50/1.4 is better than the 50/1.8 in pretty much every way other than price, but as you mentioned comparing it to the 100/2.8, well, at least in robustness, it's not up there. This lens offers full-time manual focusing despite using a cheap little micro USM, and the plastic gear train they used to implement that feature is known to be prone to breaking. Now, by that, I don't mean you're guaranteed it's gonna die on you; far from it. For instance, I bought a secondhand 50/1.4 nearly a decade ago, and it still works perfectly. I don't use it all that much, but I've used it in AF mode, and I've touched up focus (or manually prefocused) using FT-M. Most 50/1.4s work just fine. All I'm saying is that the lens has earned a reputation for suffering a higher failure rate under normal operation than most other lenses in Canon's lineup, and unlike the 50/1.8, most of us would feel at least a bit of pain in the wallet if we toss a dead one in the garbage and buy another.
• The 50/1.2L would be nice, but it ain't cheap.

These lenses also exist on the used market, along with the original 50/1.8 (with focus distance scale and metal lens mount) and the old 50/1.0L, and it might be worth considering a used lens if you can find a trustworthy vendor.

As for zooms, there are a handful of f/2.8 zooms that include 50mm. Canon has two current models, for instance, that will fit your 50D: the 24-70/2.8L USM and the 17-55/2.8 IS USM. I've never used the 24-70 but its reputation is excellent. I have the 17-55, and optically, it compares favourably to the 17-40/4L USM I used to have. It has build quality at least comparable to that of your 17-85, and way better than the 50/1.8. It lacks weather sealing, but then again, so do all of the lenses you mention, so apparently that's a non-issue for you (and for me, too). There are also a few third-party f/2.8 zooms that include 50mm; I'm not familiar with them so I'll leave that topic to those who are.

If you're considering an f/2.8 zoom and believe it might be fast enough, then you should also consider a 50mm macro lens as an option. Canon's one uses archaic hardware, but my understanding is that it offers truly outstanding optics. Third-party macro lenses also tend to be among the best lenses in those companies' lineups.

Personally, with its performance/cost ratio, I'd just buy another one and be set for a few more years. If paying out more money up front is better than doling out installments every few years, then the 50/1.4 is probably a better deal - but I do like the light weight of the f/1.8.

As far as I know, none of the third-party lens manufacturers make fast 50s.

Sigma's 50/1.4 HSM is a terrific lens. Arguably better than anything Canon or Nikon make to do the same job or even close to that price range - especially if you're using it for portraits and want good looking bokeh behavior. There are many threads on this site that discuss it as a consideration among the Canon options - a little searching will show you opinions as well as many examples of the output.

I second the Sigma 50 F1.4. I looked at a lot of reviews of this lens and they consistently say it is better than the Canon 50 F1.4. If you do a search through photo.net you will see a lot of forum post on this lens.

Oh yeah - I'd forgotten about the relatively new Sigma 50/1.4. Sorry about that.

You're really spoilt for choice considering that pretty much everyone made a great 50mm.My favourite is an old Pentacon 1.8 manual M42 mount lens - dirt cheap and very easy to replace - and truly a great lens IMO.
With this in mind - If it were me - I probably would not spend a heap of money for a 50mm because, like I said - there were so many great ones, It may be difficult to aperciate the difference in some of the more expensive ones, considering the 50mm lenses were pretty easy to make as appose to the wides and teles.
If it were me.. I'd stick with the prime as appose to the zoom. You will always (well in most cases) get a better image quality with regards to there being less glass. But if you feel a zoom may benefit your shooting style itmight be worth the cons.
If you don't mind a manual lens - something I love - having a real aperture control instead of fiddling with buttons etc.. you can grab some amazing quality - very fast lenses, very cheaply.
Don't know why but I find autofocus even takes the fun out of it for me.