Something non-political to pass the time until Fitzmas. This has come up every now and then in open threads and the occasional diary: What makes a good digital camera, and how do I pick one? This diary attempts to answer these questions.
An overview: First, I'll discuss some of the terminology used to describe various aspects of cameras. Second, a discussion of megapixels and how many you really need. Third, digital vs. optical zoom. Fourth, an overview of the different types of cameras and what sort of features you can expect to find in each class. Finally, some random tricks and thoughts.
Section One: Terminology
Some common terms and technologies that you'll encounter in camera descriptions.
The lens. One of the two key parts of the camera. Lenses have two numbers to describe them; focal length and aperture; both are usually printed on the side of the lens. Focal length tells how much magnification a lens has; smaller numbers correspond to less magnification (and a bigger field of view). Most lenses today are zoom lenses, i.e. they can vary their focal length. A 3x optical zoom, the most common lens type, typically has a focal range of 38-110 mm. The aperture is a measure of how much light a lens can collect. More light is better, because that means the photos can be taken in a shorter time, minimizing the effects of vibration. The aperture is the number with the f/ in front of it; f/2.8 or f/4 are typical values. Here, the smaller the number, the bigger the maximum aperture. If you are comparing two cameras, otherwise identical, and one has an f/2.8 lens and the other has an f/4 lens, go with the 2.8.
Memory. Digital cameras store their pictures on flash memory cards of various types. CF (Compact Flash) is found in higher-end cameras, but at the consumer level is now fairly rare. SD (Secure Digital) is the most common type, used by most makers. xD is another type, used by Fuji (I think) and one or two other companies. Sony goes it alone with their MemoryStick card. Since most cameras come with piddling little cards in the box, you'll need to buy more memory. I'd recommend starting with one or two 512 MB cards, and buying more if you decide you need them.
Image stabilization. Also known as Anti-shake, Vibration Reduction and a couple of other trademarked terms. These are technologies which consist of motion sensors in the camera connected to motors either in the lens or on the sensor. The lens/sensor is moved in such a way to cancel out the vibrations in the camera (since no human can hold a camera perfectly steadily). It can make a big difference, especially for cameras with big optical zooms:
Stabilizer off and on respectively.
Most commonly found on superzoom cameras (see part 4 below), this technology is beginning to creep into the smaller cameras. At the moment, Panasonic is the only maker including the feature in cameras of all sizes, but I expect that the other manufacturers will soon follow suit.
Batteries: Most cameras use either AAs or Li Ion battery packs. If your camera uses AAs, chances are it ships with a set of alkaline batteries. Buy a good set of NiMH rechargeables and a charger; the camera will last longer before the batteries need to be charged and you'll save money in the long run. Li-Ion batteries tend to last longer, but they do have the disadvantage that if your battery runs down, you can't just pop into the nearest drug store and buy an emergency set of AAs.
Section Two: Megapixels
More is better, right? Well, not necessarily. There are a few things to keep in mind when trying to figure out how many megapixels you should get. The first is "how many do I need?". This turns out to be equivalent to asking "what am I going to do with my pictures?"
If you are going to keep the pictures on your computer, show them to people on the screen, email them to friends, post on the web, but not print them, you don't need very many megapixels. Even a 2 megapixel camera will produce an image that can fill a computer screen, and bigger pictures give big files that are unwieldy to email/post. These days, 2 MP cameras are rare, so if you fall into this category, consider a 3 or 4 MP camera.
If you are going to print your pictures, you may want a higher-resolution camera. How high depends on how big of a print you want to make. For "standard photo prints" of 3x5 or 4x6 inches, a 3 MP will have enough resolution to do a decent job. For 5x7s, consider a 4 MP camera. If you want to make full-page (8x10) prints, 5 or 6 MPs will be needed to get a sharp (non-blurry) print. The 7 or 8 MP cameras can produce larger prints.
Higher-resolution cameras are more expensive, often by a large margin, than their lower-res cousins. Figure out what you are likely to want, and don't overbuy.
Section Three: Digital vs. Optical zoom
Camera makers breathless advertise enormous zoom capbilities for their cameras. "12x Combined Zoom" is a common claim. Beware. They get these big numbers by combining two very different things. Optical zoom is the real deal; additional magnification by moving lens elements around. Digital zoom, on the other hand, is only slightly removed from being a scam. What digital zoom does is look at the image the camera just shot and try to imagine "what would the image look like if the camera had more zoom". In essence, it's making up information. No, this doesn't work very well.
A concrete example. We start with an image taken at 3x optical zoom (note: all images scaled down to fit in your browser; click on each one to see full-sized versions)
That's kind of small. So, what does is it look like if we turn on the camera's 4x digital zoom, for 12x combined?
Not too bad. But now, compare it with the same image taken at 12x optical zoom:
This looks a lot crisper. You can make out the pleats in the statue's robe, the rails on the catwalk are clearer, etc. The comparison is even more stark if you click on the images to look at the full-resolution (3 megapixel) versions.
When comparing zooms on cameras, look only at the optical zoom. Ignore the digital zoom or the combined zoom. It's that simple.
Section Four: Camera Types
I'll cover the common subclasses of digital cameras, picking representative examples from various manufacturers. The ordering is by physical size, from smallest to largest.
Ultra-compact
Sony CyberShot DSC-T7
These cameras are designed to be as small as humanly possible. This entails some compromises in the design; there are limits on how small a lens can be before its quality starts to degrade. Similarly, the small case means that the control buttons on the back are often quite diminutive, so these cameras can be hard to use for people with big fingers. Their size makes them very popular, though, as they can be slipped into a pocket or a purse with very little trouble. Again because of their size, they tend to be somewhat more expensive than comparable compact cameras. 3x optical zoom is near-universal in this class. Most of these cameras are purely automatic, with auto modes and scene modes only. A 5 MP camera will list in the $350ish range, 7 MP lists for about $450.
Compact
Nikon Coolpix 7600
The compact class encompasses a large chunk of the models available today. These cameras are larger than the ones discussed above. The additional size gives the designers room to put in a bigger lens, bigger (and thus longer-lasting) batteries, easier to use buttons, etc. These cameras can fit in a jacket pocket or similar. Optical zooms range from 3x to 6x, megapixelage from 4 to 8 MP. Higher-end models allow for manual control of shutter times/etc. The price varies from around $200 for a 4 MP/3x zoom, to $500ish
for 8 MP and 6x zoom.
Superzoom
Panasonic FZ5
The defining characteristic of this class of camera is a whopping big lens out front. Optical zooms of 10x to 12x are typical. The screens and buttons etc. are comparable to the compacts. If you want a superzoom camera, I strongly recommend getting one which features an image stabilizer of some sort (see above). Fortunately, that's most of the class these days. Manual control of shutters and apertures are found on just about all models. These cameras run about $450 for a 5 MP model, and $600 or so for an 8 MP.
SLR
Canon Digital Rebel XT
The big boys. SLR cameras feature interchangeable lenses, advanced manual controls, higher-quality sensors than all of the above models, etc. They're also expensive. They start at $700 or so, and the sky is the limit. If you want the highest quality and most flexibility, this is the route to go, but it isn't cheap.
Part Five: Miscellaneous
First, some websites to find in-depth reviews of cameras and comparison buying guides and so forth:
http://www.dpreview.com
http://www.dcresource.com
http://www.steves-digicams.com/
Secondly: A trick for photographing moving objects. Most digital cameras, except for the most expensive, take a noticeable amount of time (a second or longer) to take a picture once you press the button. For moving objects, this can be a problem. One way to minimize "shutter lag" is to "prefocus" the camera. To do this, aim the camera at the object you want to shoot, and press the shutter button down half-way and hold the button in this position. The camera will focus on the object. Follow the moving object, and when the car/person/bird/whatever reaches the point you want, push the shutter button in the remainder of the distance. That's how I was able to get this shot:
Finally: remember to have fun with your toy! Technology is nice, but it's just a tool.
(Note: Camera pictures from the websites of the respective manufacturers. The dart board, statue, and air-show photos were taken by me using a Panasonic FZ5)
-dms