Digital Cameras Demystified

December 7, 2009 - 3:52 pm

Buying a digital camera can be an information overload, so in this tips and tricks piece we cut through the complicated feature lists and explain what to look for.

Digital SLR or digital compact

We start with the two main types of digital camera. In recent years, the digital SLR has become a lucrative camera to own, particularly for the budding David Bailey or amateur photography enthusiast, but what is it?
SLR stands for Single Lens Reflex. It’s a technology that allows the image from the lens to be displayed through a viewfinder exactly as it will be captured. SLR technology was invented in the 19th century, but clearly remains relevant in the digital age, providing a precision way of setting up and capturing images on high end digital cameras.

Digital compact cameras are, as the name gives away, smaller than digital SLRs. They don’t need the mirrors and prisms that SLRs use to direct the image between the sensor or viewfinder.

While SLRs mostly support interchangeable lenses, compact cameras have a fixed lens, but that’s not to say there aren’t fixed lens digital cameras with some pretty good lenses on them…

If you’re looking for a camera that’s a gateway to amateur photography, SLR is likely the way to go, whereas a compact camera is better suited for point and shoot fun that fits in your pocket or handbag.

So many megapixels

Unlike a traditional film camera where an image is exposed onto a film, a digital camera has a sensor that is broken down into a grid of squares (pixels). Each pixel records a colour level and that information is used to produce the photo. The more pixels you capture the more detail you’ve got in your image. We explained how these photos can be stored in File Format Fun – Making the Right Choice.

The photos below demonstrate a 500×500 pixel image on the left (250,000 pixels – ¼ megapixel) with enlarged versions of 250×250 and 125×125 pixel images next to it. Each time you halve the dimensions of the image, you quarter the number of pixels in it – the difference in detail is obvious.

Click to enlarge

So what’s a good number of pixels (resolution) to have? Digital cameras report values in megapixels (MP) – millions of pixels. The higher the resolution the more you’re got to work with, which is especially useful if you’re going to be editing images later, or have them printed rather than displayed on the web. Just remember that it’s easy to shrink an image after you’ve captured it, but it is impossible to accurately increase the size of an image without introducing blurring or blockyness.

Cameras providing upwards of 10 megapixels are very common now, but pixels shouldn’t be taken as the defining feature of a camera.

Memory

You need somewhere to keep these multi-megapixel images – a memory card of course. Most common in digital compact cameras is the SD card, but there are others – see our memory glossary.

For modern cameras, SDHC (High-Capacity) is one to look out for – supporting vast amounts of storage space you’ll spend less time switching between cards and more time snapping.

Lenses

There’s little point in having an army of megapixels at your disposal if the piece of glass focusing light onto the sensor is pitiful. Lenses aren’t a simple area, especially for SLR cameras, so we’ll stick to the basics of compact camera lenses.

A wide-angle lens for an SLR camera

One of the key figures quoted is the focal length of a lens, in millimetres. A shorter focal length provides less magnification but a wider field of view, which means you can capture a wider shot. To put it another way, if you’re trying to take a photo of a big group of people, you either need a wide-angle lens, or have to stand far back.

It’s impossible for us to declare what lens is best for you, but as long as you know that it’s as important a feature as the resolution of the camera – reviews will be your in-disposable assistant here.

Zoom

Zoom is another characteristic of lenses (or is it? keep reading…), where the focal length of a lens can be changed in order to magnify far away objects.

Zoom is generally stated as a value such as “4x” or “8x”, which describes the difference in length between the smallest and biggest focal length of the lens. 4x 25mm gives 100mm, so a lens that can range between 25mm and 100mm has 4x zoom.

Obviously the higher the zoom factor the more magnification can be had, but as it’s based on focal length, not all zoom lenses are equal even if they report the same factor of zoom.
You can spot a zoom lens really easily, because it will move in and out when adjusting the zoom level on the camera.

But what if nothing moves when you zoom? Chances are you’re not really zooming at all! Welcome to “digital zoom”, which isn’t so much zooming as chopping away the edges of an image and enlarging what’s left. The camera might have features to help enhance the digitally zoomed picture, but we prefer to avoid digital zoom and do cropping and resizing in a photo editing program later on.

Modes

Hmm, I wonder what that one does...

Modern digital cameras are clever little critters. Many of them have all manner of operating modes to help you get the most out of your scene. The list of possibilities is longer than this page should ever be for the sake of everyone’s sanity, so here’s just a few:

Auto

Yes, of course, the “I don’t care, just take the photo” mode. Truly point and shoot – let the camera worry about pretty much everything.

Program mode

Some cameras let you tweak some of the settings while leaving the rest automatic. Useful if you want to make tweaks to sensitivity, white balance, exposure compensation and some of the other aspects you’ll become accustomed with on the road to becoming a camera geek.

Manual mode

Opens up all of the cameras settings to you, giving you more control (or more to mess up, depending on which way you look at it). Sometimes humans are better than microchips at working out the best settings, in which case this is the mode of choice.

Macro

For shooting small or very close objects. The capabilities of your camera’s lens are important here too.

Scene/preset mode

Certain shots look best within certain constraints – no point turning the flash on for a photo of some fireworks, right? Lots of cameras support various presets that help take some of the guesswork out of getting the settings right for a particular shot.

Burst

It’s hard to capture exactly the right shot, especially when your subject won’t stop moving. Burst mode takes a series of photos in quick succession. It’s good for capturing an action sequence, or simply hedging your bets when shooting a group of people. Some cameras can burst more quickly than others, so it’s important to know how quick they are. The speed of the memory card is important here too.

Batteries

How many photos will a camera take before it needs a change of batteries? What type of battery does the camera take? Important questions indeed.

Battery requirements and performance vary from camera to camera.

Obviously, the longer a camera lasts on a battery the better. Some cameras take standard AA or AAA batteries, while other take custom battery packs. Custom batteries can be expensive, but often perform better than standard batteries by virtue of their lithium-ion innards. If you’re thinking about carrying around a spare battery, it’s worth finding out how much that’s going to cost you before selecting your camera.

Movies

Most cameras can capture movies now, but the quality varies wildly. They tend not to compare too favourably to proper digital camcorders, but for casual videos they can be more than adequate.

If you want to grab the occasional movie with your digital camera, make sure it’s got a microphone built in – some cameras only capture video and not sound! Next, check the resolution – a growing number can now capture 720p high-definition (HD) video, giving you more detail in the recording.

Videos take up a lot of drive space, so as with high resolution images, make sure you’ve got memory cards that can accommodate your needs!

Is that all we need to know?

The exciting thing about photography is that there’s so much to learn – so many photos that have yet to be imagined, let alone taken. We’ve only scratched the surface, but hopefully we’ve helped the photography novices on their way to finding a digital camera that suits their needs.

If you have any helpful advice of your own, be sure to let us know by commenting.