As an upgrade from kit lens 18-55mm, which would be a better general purpose lens?
Obviously there is no "best" option, as everyone has a different budget and style, but what are the best options when upgrading, and why are those options superior?
If you only want to carry one lens,
and want your new lens to have at least the same capabilities as your kit lens, you have two basic options: a fast zoom, or a superzoom.
This would cover a very similar focal length range as your kit lens; generally 17-50mm or 17-55mm, but have a constant aperture of f/2.8. Not a big deal at the wide end, but that's two stops (4 times) faster than your kit lens all the way zoomed in. This would let you take pictures in lower light without extra noise, and can have shallow depth of field. Some examples:
A superzoom is a lens with a very long zoom range, covering both wide angle and telephoto. Your kit lens has about a 3x zoom; superzooms have 10x-15x. Generally, these aren't any faster than kit zooms, with a typical aperture range of f/3.5-f/5.6. These let you change composition without changing lenses, but won't generally win any awards for sharpness, low light abilities, or distortion.
If you're willing to carry more than one lens,
you can get more of a specialty lens, that solves one problem very well, instead of the very general-purpose lenses above. You've got 3 basic options for this: a wide zoom, telephoto zoom, or a fast prime.
A wide zoom will let you get a much wider angle than the 18mm widest setting on your current lens, such as 10mm or 12mm. Some of these will be fisheye lenses, which produce severe distortion; others will be rectilinear, which means they produce a "normal" image, where straight lines in the world are straight in the image. Some fisheye lenses can provide a 180° (or more) field of view. Wide angle lenses often suffer from noticeable distortion, chromatic aberration, and vignetting, but this is usually better with a moderately stopped-down aperture and at the less-wide end of the zoom.
A telephoto zoom would have a "wide" angle of somewhere around 55-75mm, and a long end of 200mm or more. Telephoto zooms can be sharper, less distorted, cheaper, and have faster autofocus than a superzoom with the same reach, but you have to switch back to your kit lens if you want to zoom out far enough. You can also get telephoto lenses with faster apertures, like f/4 or f/2.8, but these can get pretty expensive.
Apparently, Sigma also makes a 50-500mm f/4.5-6.3 lens, which I guess would be a telephoto superzoom.
Fast primes are the kings of low-light photography. These generally have apertures of f/1.4 to f/2.0, though there are some f/1.2 and faster lenses out there. A basic fast prime like a 35mm or 50mm is a great second lens to get; they can be pretty affordable, and can be 8-16x faster than your kit lens at its telephoto end. Because they don't zoom, these can be incredibly sharp, have low chromatic aberration, and have very low distortion. The very wide aperture can create a very shallow depth of field, leaving everything but your subject out of focus.
Note: This isn't an exhaustive list of lenses; I tried to give a representative sample of the lenses you might look at in each category, but I left out many lenses. Also, I shoot Nikon, so I can't personally recommend any of these lenses. I suggest you research each lens you're considering.
I think the Tamron 17-50/2.8 (Non VC version) is natural upgrade to your lens if you want to replace it with something more functional without too much cost. Reviews suggest that the Non-VC version performs much better than the VC version. With f2.8 you have a really fast lens that also gives you a lot of shallow DOF.
With regards to price it beats competing options from Canon or Nikon by a lot. You do sacrifice on build quality but it should be better than the stock lens.
Take a look at the reviews:
If you want to go telephoto then the Sigma 70-300 or Canon 55-250 both with VC should be helpful. For Telephoto VC is definitely a big must. You can easily notice the difference. The Sigma can be a better choice than the Canon given it will give a larger focal length on a APSC SLR.
Take a look at the reviews:
Both are lenses are going to give you different options and are for different purposes, so that choice depends on what exactly you want to shoot.
My personal opinion would be to go for either:-
Basically my rationale is as follows. I'm guessing that as you mention upgrading from the kit 18-55, that you're using an APS-C camera body. The 50mm lens makes for a great general purpose everyday lens, that also doubles on APS-C as a great portrait lens. It really is superb both in terms of being small and lightweight, having a really large aperture to allow for good control of depth of field, and really nice image quality. It also serves as a good stepping stone into the world of prime lenses, and whilst you may be initially hesitant and uncomfortable without the convenience of the zoom ring, once you get used to it, you just won't go back. It's also a cheap-ish lens, around £300, though if you want, there would be no problem going for the f/1.8 version which is even less - around £90-£100.
As for the 17-55, if you want a zoom to replace the kit 18-55, then this cannot be beaten. It has almost the same zoom range as the kit lens, but has a constant f/2.8 aperture through the entire zoom range, AND image stabilizer built in. L-quality optics with aspherical elements and low-dispersion glass, but in an EF-S body - which itself should produce a sharper image on an APS-C body. It's a bit of a beast of a lens - there's a lot of glass in there - and it's not so cheap either (about £750?)... But I used one for about 18 months and it really is fantastic. I was very happy with it indeed and the only reason I did sell it on was because I switched over to primes.
I would go with the canon 24-105, maybe not as wide but a very good quality lens. Or even the 24-70, a favourite among wedding photographers.
If you ever planning on upgrading to a full frame you'd then be able to use the above lenses, versus by efs lenses that will only work on crop sensor cameras
If you don't have much money:
If budget allows I recommend the Canon EF 24-70mm f/2.8 L USM Lens. I cannot put into words how much I love this lens. Sharp quality and a decent range keep this lens on my 7D 95% of the time. The price is around $14-1500 but this is a lens that you will want to keep even as you upgrade your camera body. Canon's L lenses also hold their resale value should you ever decide to sell. These were all factors that went into my own decision to invest in this lens. There are plenty of reviews out there so just google the name (apparently I don't have enough reputation points to post more than two URLs).
On a side note, I do not bother with third party lenses. I buy only Canon lenses and if I shot on a Nikon would only buy Nikon lenses. Why? Well, Ken Rockwell sums it up fantastically:
(Full article) http://www.kenrockwell.com/tech/nikon-vs-canon.htm
After reading that article I made the decision to get rid of my Sigma lens and go Canon. Scott Bourne had a recent blog post that further supports this decision:
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