Having worked in the photographic retail business for a while now, there's one thing that really strikes me, most people go into stores without knowing what they really want or need. In this article I aim to give you an idea of what you should be looking for when you purchase a new digital camera.

I have sold the most expensive cameras to rich businessmen who just want o take snapshots, but want the "best" and I've sold compact cameras to people who want "lots of megapixels".

These are two very common scenarios and it often leads to the person not actually getting the camera that is right for them. Let’s start by dispelling these ideas.

Firstly, just because it costs £6,000 does not mean that it is going to be the best camera for the job. The new Canon 1Ds MKIII, for example is the most expensive dSLR on the market, it has 21 Megapixels and a Full Frame CMOS sensor. But because it is a pro camera it needs to be used manually, it cannot just be put on automatic and pointed, it also is an extremely heavy camera certainly not something you could just throw in your bag and go off out for a day. It's great for fashion shoots and high detail landscape shots, but not for pointing and shooting.

Secondly, various manufacturers produce 12 Megapixel compact cameras, sure you will get a huge image from it, but because it's a compact camera, everything about the camera is compact, it lacks the functionality and control of a dSLR, they're also usually slower and less responsive meaning you might miss the best shots. Also, because of the cost of producing something to that scale they're quite costly compared to other compact cameras.

Terminology

1) I've talked about them already, Megapixels (or megapixies as someone once said).
What is a Megapixel? A Megapixel is a million pixels, most of you are probably aware of what a pixel is, it's a little block on a camera sensor that traps information for your camera. They come in different sizes, shapes and flavours depending on who made the camera but the basics are always the same.

How do Megapixels affect the final image?
In theory, the more Megapixels you have the larger the image is. The biggest myth about Megapixels is that the more you have the better the quality of the image. That's only half true, whilst it's true that if you tried to produce a 30 by 20 print from a 6 Megapixel compact camera the quality would be lower than that of a 12 Megapixel compact camera. If you were comparing 10 by 8 prints then you would likely not notice the difference.

2) Sensors.
Every picture you take is initially recorded by your sensor (which is composed of Megapixels) Most compact cameras have quite a small sensor compared to the larger scale "prosumer" cameras, which again have a smaller sensor than the ones on dSLRs. Sensor size is very important when it comes to your picture, the larger the sensor is, the more detail it will get in the picture. Why is this? simply put, it gives the pixels more room to breathe. If you want a little exercise to demonstrate this grab a piece of paper, mark on it a 1cm by 1cm square. Now grab some pins, the ones with the little ball heads. See home many pins you can get on there before they interfere with each other. Now use a 2cm by 2cm square and so on and so forth.

In the world of electronics we call that interference "noise", because a pixel is a little electrically charged unit it vibrates slightly, the more pixels you have in a small area they're all going to start vibrating and the data that one pixel gets is tainted by the vibrations of another. This noise will show up on the picture, it gets worse as you use higher ISO settings.

If that was too much to follow, here's the short of it. In my experience, with a compact camera the optimum is 7 Megapixels, with a "prosumer" camera 10 Megapixels, with a dSLR theres no limit as such, it is also dependant on the type of sensor that is used.

3) ISO.
Simply put, the ISO is the sensitivity of the sensor, the higher the ISO, the faster the pixels vibrate, which means they can capture more detail in low light settings, but like with having too many pixels too close together the noise starts showing up on the pictures. For most cameras the levels of noise at the same ISOs are similar.

4) Anti-Shake/Anti-Blur/Noise Reduction.
One thing some manufacturers are employing now is digital noise reduction built into the camera, sometimes they will market it as "digital anti-shake" but the thing you must always remember is that it is digital noise reduction, the image is run through a process before it gets out of the camera, this process, whilst cutting down on the appearance of noise is destructive to the level of detail in the final image.

However, there are a few manufacturers that produce cameras with Optical Image Stabilisation. These are most notably Canon, Nikon, Panasonic and Sony. The way that they all work is by moving something to correct against shake. In the case of everyone but Sony, they move an element inside the lens, making sure that the image coming from the lens is projected straight onto the sensor. Sony use a different method, they use the old Konica Minolta method of vibrating the sensor against the shake. Whilst the Sony method means that the image can be stabilised no matter what lens is used, it's not as effective as stabilisation in the lens. Also, be aware that Sony only use this technology in the dSLR as far as I am aware, they use a digital method in the compact cameras.

5) Focal Length.
The focal length of a camera lets you know how big the zoom is. In compact cameras they will use a number like 3x, 4x and so on. Focal length can seem quite confusing, all it is actually a measurement of distance from the focal plane of a camera (point where the image is taken) and the end element right at the front of the lens. It's easiest to think of this in terms of viewing angle, the smaller the number is the wider the viewing angle and vice versa. Because compact cameras use much smaller sensors than dSLRs the focal length is much smaller, which is why they use the multiplication scale, it is much easier to market.

6) Cropped Sensor.
You will usually hear this only in relation to dSLRs but it also plays a role in compacts too. It refers to the size of a digital sensor in comparison to a 35mm film negative. Most dSLRs are approximately a 1.5 crop, which means that they are 3 quarters the size of 35mm negative. The exception are Olympus, who use a 2x crop, their sensors are half the size of a 35mm negative. Also, there are some Full Frame dSLRs, these as you can guess are the same size as a 35mm negative. Currently only Canon, Nikon and Kodak produce Full Frame dSLRs. With a larger sensor there is more room for the Megapixels, which is why cameras with full frame sensors produce higher detail images and have more Megapixels.

7) Macro.
There is a slight misconception about macro. Macro is not just "close up". A "true macro" is one where the subject is displayed 1 to 1 on the sensor, that is to say "life size" or larger. More recently however manufacturers have been marketing lenses capable of lower sizes as Macro, sometimes even as low a 1 to 4 ratio (quarter of the size). Also many compact cameras use a digital macro mode to enhance the image further.

8) Frames per Second (FPS).
This is most common in dSLR, it refers to how many shots a camera can take in a second. Unless stated otherwise most cheaper dSLRs can take 3 frames per second. Higher FPS is essential for sports photography when you do not have a lot of time to keep taking and checking a shot, it can also be helpful when photographing children playing.

Choosing A Camera.

When choosing a camera you need to consider, your budget, what you want it for, how heavy it has to be and how much you know about photography. It may sound cruel, but if you're just starting out in photography you don't need to buy the most expensive camera you can get your hands on, it really will only set you back. When it comes down to budget, these days entry level dSLRs are not that expensive, they're now not much than a decent compact camera or "prosumer" camera, so if you're really interested in photography, I would advise you to start there. Something like the Nikon D40 or Canon 400D (Rebel XTi) will only set you back around £350; it really is worth the extra £100 or so over a compact camera.

When it comes down to Canon and Nikon there is a lot of arguing over which is better, in reality there is not much difference at the level most people are looking at. Speaking as a Nikon user, I can quite happily say I have sold and suggested that many people by Canon, because it was the most suitable camera for them. It's all about what you prefer; Nikon and Canon menu systems and camera layouts are quite different. However, both have a very similar range of lenses and accessories available. Olympus, Pentax and Sony don't have anywhere near the range available.

Choosing Accessories.

When buying a camera of any sort you will need a memory card. Memory cards come in different formats and apart from compact flash, there is no huge advantage of one format over another. Compact flash cards allow for high speeds and larger capacities; however most cameras will only take one format of card. Each format has a low speed and a high speed option, this relates to the data transfer speed the card is capable of. Most cards will list the data transfer speed on the back either as a Mbps (e.g. 8Mbps) or a multiplier (e.g. 33x speed). For compact cameras only the basic speed memory card is necessary, the transfer speeds inside the camera and the size of the image do not usually require a faster card. For entry level dSLRs you won't need a card faster than about 66x write speed, a card like the Sandisk Ultra II is more than fast enough for the camera. Only when you start looking at cameras like the Canon 40D and Nikon D200 (D300 to arrive shortly) do you need to look at something faster, like the Sandisk Extreme III.

When it comes to size of card needed that is down to how many pictures you would like to store and in what format. Any store assistant worth their salt knows how roughly how many images can be stored on a card with a particular camera.

I would also seriously recommend you take into consideration the requirement of a carrying case, when you're spending a few hundred on a camera; you really ought to be thinking about keeping it safe.


Future Purchases.

When you buy a dSLR always keep your mind open about possibly wanting to buy additional accessories in the future, like different lenses, tripods, filters and flash guns.

A good dSLR should last you a long time and it's not something you should just jump straight into. Always research a camera before buying it, dpreview.com is a good site to check out, as they have full impartial reviews of all the latest cameras. Be careful with some magazines as they can sometimes be sponsored by a manufacturer to promote their cameras.

If you have any further questions about buying a dSLR don't hesitate to drop me a note or put a question here. I may do another article that goes into more detail about camera accessories if you guys would like one.