Here is an article I published on my website about the number of megapixels needed in a digital camera. I hope it'll be useful to some of you in this forum.
How Many Megapixels Do You Really Need in a Digital Camera?
by Gary Hendricks
If you're out buying a digital camera, then one of the key deciding factors is the number of megapixels supported. The number of megapixels determines the how good your photos turn out. If you have too few megapixels, then your pictures will turn out crappy. Investing in a camera with too many megapixels, on the other hand, is an unnecessary waste of money.
Personally, I feel that if you have unlimited funds, then, by all means go for that high end 8 megapixel camera. Otherwise, you certainly don't want to waste money on extra megapixels you don't need.
A golden rule to bear mind: a camera with more megapixels isn't always better. If your camera supports more megapixels, then each photo you take will be larger. This means that you'll use up more space on your memory cards and computer's hard drive.
If you have trouble deciding how many megapixels you need (I know I did when I bought my first digital camera), then the guide below will help. Essentially, you need to ascertain what size prints you want to get and what your budget is, before deciding on how many megapixels you want. So here we go:
1 megapixel or less: Cameras in this range (e.g. web cameras or cell phone cameras) have very low image resolution. Don't expect to be able to print high-quality photos using these cameras. You can, however, email the photos or post them on your web site. The good thing about such cameras, of course, is their low price.
1 to 2 megapixels: My first digital camera was a Canon PowerShot S110 which only had a 2 megapixel sensor. Cameras in this range are pretty decent though - you can expect to print out great 4x6 prints at this resolution. Of course, if you want larger, blown-up protraits of your birthday party or holiday in Italy, then I would certainly recommend getting more megapixels. Cameras in this range should sell for around $100 currently.
3 to 4 megapixels: Most new point-and-shoot cameras these days tend to have at least 3 to 4 megapixel image resolution. Bring these images to the lab and they'll be able to develop great looking 4x6, 5x7 and even 6x9 printouts. Expect to pay slightly more though - we're looking at around $250 for a good model.
5 megapixels and up: The more advanced cameras tend to have image resolutions of 5 to 8 megapixels. Newer point-and-shoot cameras have 5 megapixels, while the newer digital SLRs come with 8 megapixels. The quality of images shot by these cameras is simply stunning. Of course, their price tags are equally stunning . In this megapixel category, expect to pay around $300 for a 5 megapixel camera and up to $1800 for an 8 megapixel SLR.
Well, now you know roughly the number of megapixels you should be shooting for depending on your intended usage and budget for the camera. My general advice is, if you're just an amateur photographer, then don't buy cameras above 5 megapixels. When you are really serious about digital photography and want to go professional, then consider buying a super high megapixel camera.