I am thinking of buying a digital SLR camera. What things should I be looking for?
Things to look for when buying your first dslr:
My first dSLR was a Canon 20D, a prosumer body. I chose it because I have larger hands, and the 20D size and weight felt better (twss), and I wanted something I could grow with.
The general answer to this question is: whichever gets you done with worrying about what camera to buy the fastest.
For some people, that means get whatever low-end equipment you can afford to start playing around — get an entry-entry level camera which strikes your fancy plus the kit lenses (and hopefully a decent prime). Treat that as basically disposable and use it to figure out your style and needs for the next step. For others, it might mean skipping that and going right to the higher end — short-circuiting years of longing and painful not-quite-there upgrades, arguably saving money overall.
One can actually do very high quality work with any DSLR on the market today. If you're in this for the long haul, what you start with doesn't really matter; what matters is getting started. If you later feel you made a mistake, changing camera bodies within the same brand isn't a big deal. Changing systems can be more of a challenge, but if you go the low-end entry route you won't have as much to worry about, and if you go the higher-end route the equipment should retain pretty good resale value. So don't be too scared to just jump in.
I do understand the desire to research before making a big purchase. There's nothing wrong with that to some degree, but it's easy for people of a certain mindset to go too far — a warning I feel well-qualified to give because I personally naturally fall pretty far on the side I'm cautioning about. So, despite the bold text above, I am going to thrown out a few more things to consider; specifically, I think the following questions and their answers are some of the most helpful on this site for anyone making this initial DSLR decision:
Find out what brand of cameras your photo friends own. The relative differences between Canon and Nikon are fairly small (and probably don't matter until you get very advanced), so a big advantage when starting out is buying the brand the people you hang out with have bought. That gives you a source of free advice, plus the ability to try out cameras and borrow lenses to see how things work.
Don't overbuy. You can buy a really good camera in the entry level; even if you outgrow it, having a second body around is a good thing, or you can sell it and upgrade. If you get serious about this, you probably WILL outgrow it, so don't overspend. Buying more expensive cameras means buying features you won't need, use, or understand and might make growing into the hobby harder and frustrating. The Canon Rebel is a great way to get started.
Do you really need a DLSR? There are some really nice cameras that just don't happen to have interchangeable lenses. We've used the Panasonic Lumix superzooms for years, the current model is the DMZ-fz35) and it can turn out really nice pictures without many limitations. Another is the Canon G11. Consider whether you need a DLSR or whether you're really looking for a good entry level camera (how badly do you need/want interchangeable lenses?) -- some of these high end point and shoots match entry level in image quality and are less expensive and more convenient.
if you stick with a DLSR, figure out your lenses first, and don't cheap out on them. Assume you'll upgrade your camera body 2-3 times before upgrading your lenses -- if you pick your lenses well. So be willing to spend a bit more on lenses and buy a less expensive body. It's a good investment. Avoid "kit" lenses that come bundled with bodies. waste of money, IMHO.
I like as an entry level set something like the Canon Rebel and a good third party lens with a decent superzoom capability, like the Sigma 18-200 (I wrote a bit about why I prefer that lens to the Tamron I actually own here: http://www.chuqui.com/2010/01/a-few-thoughts-on-lenses/) -- the cost difference between the rebel with a kit lens and the rebel body only is about is about $250-275. You can buy the body only and the sigma for pretty much the same money and get a much better and more flexible lens..
consider renting a camera for a week with the lens you're considering. Make sure you like the results, make sure it's comfortable in your hands.
Things to consider when thinking of purchasing your first dSLR.
1. Can I afford a dSLR?
If you've never used an interchangeable lens camera system before, realize that the cost is astronomical in comparison with fixed-lens cameras, because the camera body itself is just the start of your purchases and the basis of your system. It is also (weirdly) the most disposable piece of gear these days, unlike film camera bodies. That's digital electronics vs. mechanical devices for you. A single lens can easily outstrip the cost of the body. Support gear, lighting gear, filters, bags, etc. It can all mount up with surprising ease. IMO, you probably need 2x or 3x the amount you spent on a body/lens kit to get a basic system with a dSLR. Think in terms of US$1000-$1500, not $500, for a basic (low-budget) dLSR setup and about twice that for an extended or higher-quality setup. Needless to say, many of us spend a great deal more.
2. Do I need a dSLR?
Four or five years ago, it was P&S vs. dSLR, so the decision was pretty clear. But today, there are quite a number of fixed-lens compacts with sensors and lenses rivaling dSLRs, and the entire class of mirrorless interchangeable lens cameras has appeared. What and how do you plant to shoot? Are you ok lugging 20 lbs of gear with you? 5 lbs? 1 lb? Do you hike for miles into the mountains to reach your landscape shot? Do you need to be silent and unobtrusive for street shooting? Do you plan to work in a studio? dSLRs are larger and heavier, and are the best cameras for fast action responsiveness, and as more mature systems have the largest options for expansion, the best used markets, and the largest 3rd party support. By comparison, mirrorless systems have only been around for a handful of years. But they're smaller, lighter, seeing astounding amounts of innovation, and yielding image quality at the level of dSLRs, but have smaller overall systems and less 3rd party (think: lenses, flashes, flash triggers) support from being so young. So, what/how you shoot also determines which type of camera might be better for you.
Features come and go and play leapfrog across brands and models. All of the cameras are good. None of them are bad. What you have to look at is the system overall.
3. What lenses will I need?
Don't think of lenses as accessories for your camera body. We know, P&S cameras have trained you to think this way, but your camera body is actually the accessory for your lens collection. Sensors and bodies come and go. New camera body models are introduced and then depreciate at an astonishing rate. A lens, however, may not see a "replacement" for decades, if ever. Lenses often hold value in the long term, and in some cases, can even appreciate. Look to the glass. Canon and Nikon are often touted as being the best systems to look at simply because they have the largest selections and any 3rd party lens made for other brands are made for them, too. But Pentax makes pancake lenses. And Sony has Zeiss glass in its lineup. Learn about focal length, max. aperture, and what type of lens you might need for what you want to shoot. Then see if the mount system you're thinking of buying into has those lenses.
4. Am I OK with giving up P&S convenience?
The focus on most articles about "upgrading" from P&S to dSLR emphasize the gains. Not many talk about the losses. dSLRs, by default, don't do as much in-camera processing as P&S cameras. This is to give the photographer the choice of relying on the processor in the camera, or to tweak to taste by individual image with the RAW data. Are you prepared to get post-processing software and learn to use it? P&S cameras have small sensors and small slow lenses so that you can't misfocus easily. dSLRs let you misfocus all you want. That's how you get that bokeh you think you need so badly: having things out of focus. You'll have to master focusing the camera. P&S cameras have tiny lenses with very deep depth of field--so they can do macro. Bigger sensors and bigger lenses mean larger minimum focus distance. To do macro on a dSLR, you probably need a $400+ macro lens. You ok with that? Bridge P&S cameras have superzoom lenses that give you the equivalent "reach" of 500mm and 600mm lenses on a full-frame camera. Those types of lenses cost $1000+ on the dSLR side of the fence. You ok with giving up that reach? You will get a lot of gains from moving to a dSLR, but this isn't a straightforward "upgrade" in all areas: you are shifting from one type of tool to another. And of course, you're liable to be lugging a bag of gear around with you, not just slipping a camera into a pocket or purse.
Most anyone who shoots with a dSLR will also have a compact camera as well for the added convenience. For most it's not "or"; it's "and". Think of it like big red toolboxes (that you still have to buy tools for) and swiss army knives. Tools for the task.
So, I recently bought a used camera. To decide which to buy, I developed this technique:
This method is a little complicated, but it pays off. It made it clear to me which camera was the best deal.
Most cameras nowadays support much the same options for using an aperture priority or shutter priority modes, as well as your full auto options, so that isn't a great way to set them apart. Most of the major brands will give comparable image quality too.
When thinking about cameras specific to a task, you need to think about how you'll use it; In the case of landscape or wildlife photography you might want to consider features such as weather proofing, and differences between models. It is also important to consider weight if you're going to be carrying it around (along with lenses, tripods, waterproof clothing, kitchen sink, etc.)
The tricky part about landscape and wildlife is that they sometimes imply different, if not opposite requirements. Landscape often demands a camera/lens combo that can capture as wide a scene as possible. Wildlife usually requires one that can zoom as far as feasible to capture an elusive animal from a safe distance.
To take pictures of a large landscape you can either stitch several photos together, or rely on a wide angle lens (in the 15-30mm range for example). The size of the camera sensor here is important. If you have enough resource to buy a full frame (35 mm equiv) camera, you will be able to use wide and ultra wide lenses to their full potential. On smaller-sensor DSLRs, wide-angle lenses have smaller angles of view that depend on the corresponding crop factor.
Most consumer cameras use APS-C sensors, which effectively "zoom in" by a factor of x1.6. What it means is that your new 16mm lens behaves like a 25.6mm. Your 50mm like 80mm, etc. No matter how wide your lens actually is, you will not capture a scene as broad as if it had been mounted on a full frame camera/sensor. This is not all bad though, since a lens is usually optically better at its center anyway. Ultra wide lenses can also introduce a lot of unpleasant optical distortions.
There are two sides to this coin. What is detrimental to wide landscapes is good for distant wildlife though, because you can zoom even further with a telephoto lens mounted on a APS-C sensor. The crop factor still applies, this time to your advantage. A 200m zoom suddenly behaves like a 320mm, allowing you to get that much closer to a bird and use cheaper lenses.
You didn't mention your budget, so keep in mind that full-frame cameras are usually much more expensive than consumer APS-C cameras. They are bulkier and heavier as well, requiring sturdier tripods. They also demand better lens/glass if possible, since they are using the whole image circle.
I don't do too much landscape, but I take a lot of pictures of large abandoned buildings. In this scenario I really benefit from a 16-35mm lens mounted on a full-frame sensor. I do have a 70-200mm lens as well to shoot from a distance. If I'm willing to compromise a bit of optical quality I can always use small lens extenders to reach x1.4 to x2.0 further.
Of course, it's not one or the other. As jrista pointed out in the comments, you can capture perfectly great landscapes with a telephoto and go for a different, compressed look.
I'll assume a $1000 budget. Adjust as required.
The usual "safe" choices are Canon or Nikon (alphabetical order - either OK) but also very safe are Olympus & Sony and there are a number of entirely adequate other offerings.
No eg $1000 camera system would be the camera of choice for a professional wedding photographer BUT any wedding photographer worth their $ would be able to take reasonably good wedding photos using such.
If you especially value low light photography you may wish to look at good used lenses that have a reasonably large maximum aperture (f/2.8 or better). All camera makers also offer something like a 50mm f/1.8 prime lens at an utterly bargain basement price in terms of performance per $. Some also do a 35mm f/1.x but these are sometimes more costly enough to eat more of your $1000 budget than you can really afford.
Many entry level DSLRs have kit options with one or two low cost and relatively modest quality lenses. These are usually lower cost when bought this way than if bought separately and the quality is usually good enough to be useful while you are learning.
"Best brand" recommendations usually bring out brand purists and the arguments never cease. I'm going to mention one brand for a special reason - you can decide if it matters enough. I started with a Minolta SRT303b film SLR decades ago due to a friend's recommendation and have used mainly Minolta and then Sony (who bought Minolta's camera business) ever since. [I also have D700 Nikon but that's irrelevant here]. Optically and functionally Sony's DSLR line is similar in performance to Canon or Nikon or Olympus or ... . There is one major difference.
FWIW - Sony make the sensors for the top Nikons, so much of the differences are in presentation and processing and not raw sensor performance.
If you already have some lenses, make sure that the camera (body) you're buying will work with (all) your lenses! I found out the hard way that the bargain Nikon D5000 body that I bought as a backup camera wouldn't power my favourite Nikon AF 80-200 f2.8, so I have to manually focus it/
I was in your position a few weeks ago, and I guess most everyone here was sometime. Mostly I went like this:
Price? (new and used)
In any case, that's me. But I think I've got you a few pointers (oh, also check if the camera is compatible with the newest lenses, I've heard that's a problem in CanonWorld)
(And if you were wondering, I got myself a Nikon D40 and two old full-frame lenses: a 50mm f/1.8 and a 200mm f/4) ("Garçon, zai vill haf a large zerving of portraits withz a side-dish of birds.")