Don't box up that camera and send it back to the manufacturer just yet. There are lots of reasons why your camera may be producing images that look great on your computer and bad on paper. The good news is that most of these issues are easily correctable once you understand your camera's settings and have a good idea about what you're going to be doing with your photos. The key is in your camera's resolution and your monitor's calibration.
Before you can understand the difference between a printed image and one viewed online, it's important to understand PPI. PPI is used to describe the resolution of a digital image; it stands for "pixels per inch" and refers to the number of pixels - or electronic dots - that appear on your monitor or in the image file itself. The important thing to remember about PPI is that the more pixels or dots per inch there are in your image, the more information there is, the more detail there is, and the better that image will look when printed at larger sizes.
Modern digital cameras can produce extremely high-resolution images. That's why everyone drools whenever Nikon or Canon adds a couple of megapixels to the latest DSLR du-jour. More megapixels equals better photos, right?
Well, yes and no. If your images never leave your hard drive, or Flickr, then you don't need all those megapixels. You don't even need most of them. That's because the resolution of your standard monitor is actually a lot less than the resolution of a good quality print. You don't need a lot of megapixels for your images to look good on the web or on a DVD. On screen, a photograph doesn't need to be much better than 72 PPI to look crisp. So if your primary motivation for taking photos is so you can share them on Flickr or Facebook, that 18 megapixel camera just isn't necessary. A six megapixel camera will be plenty. You could probably even get by with a four megapixel camera, depending on how large you want those images to appear onscreen.
Now, keep in mind that you can't add resolution to an image. I don't care what all those spy movies try to make you believe, you can't just say "enhance image" to your computer and have it give you a perfectly sharp, magnified image. It just defies the laws of photography - it's impossible to create detail where there was never any detail to begin with. Photoshop does give you the option to make your files larger, but don't. You'll end up with a larger image that is poorer quality than what you started out with. So if you have even a small inkling that you might want to print those photos some day, you need to be shooting at a higher resolution. If you don't, your images are going to look pixelated when you print them - which means you'll be able to see all those individual dots instead of the sharp, photo-realistic image that you'd like to see.
Now let's say you do have a super-awesome, super-expensive 18 megapixel camera. You don't have to shoot every image at maximum resolution if you know you're just going to be printing them out at 4 x 6. Most modern DSLRs have between five and 10 different available resolutions. All you need to do is decide which one is going to work best for your needs.
If you print all of your images at 4 x 6 and you never bother to crop them, you still don't need to buy that super-awesome super-expensive 18 megapixel camera. So what resolution do you need to get consistently good prints at this size? The answer can be found in a simple math formula: the PPI of your image should be the size of your print multiplied by 300. So for a 4 x 6 print, you will need an image with a PPI of 1200 x 1800.
Ah-ha, but lots of photographers crop their photos. What if you shot some pictures of your child's soccer game and you want to crop out the crowd? You're going to be unhappy if your shots are at a resolution that only looks good as an uncropped 4 x 6. For this reason, it's always a good idea to shoot at a higher resolution, though which resolution you choose is going to depend on your camera and its capabilities. You can always make an image smaller in post processing, but you can't make it bigger.
The drawback to shooting at a higher resolution, of course, is that you'll need a larger memory card. Your camera's highest resolution setting is going to be a memory-card hog, so you'll either need to invest in some extra cards or you'll need to balance resolution against memory space. If you take a lot of photos, memory space might be more important to you than resolution.
RAW and TIFF
Most DSLRs give you the option to shoot in RAW, which is an uncompressed format that produces an image with greater detail and a broader range of colors and tones. Depending on your model you may also have the option to shoot in TIFF, but TIFF files are even bigger memory hogs and don't actually contain more information than a RAW file.
The advantage to shooting RAW is that it is much easier to adjust the image in post-processing because there is more detail in the original file. You can also print RAW files at larger sizes than even JPEGs shot at "fine" quality, giving you much more flexibility later on.
My pictures look sharp, it's the colors that are off
If you're having issues with color rather than resolution, then look to your monitor to find the problem. Most casual computer users don't bother to calibrate their monitors, and that can make a huge difference when comparing what you see on screen to what you see on paper. Before you can view your photos online and accurately predict what they will look like offline, you need to make sure that the colors you see on your screen are the same as the colors in the real world.
To do this, you can use any number of free online tools such as QuickGamma, which visually walks you through the calibration process. Windows 7 also has its own built-in color management tool, which is a simple step-by-step process (search for 'calibrate' to find it). For the most accurate color calibration, however, you need to spend money. Of course. Hardware calibration kits like the Spyder Pro retail for about $200 but are by far the best tools available to get this right. If you plan to embark on a professional photography career, this is something you'll eventually need to own.
There really aren't a lot of fancy tricks you need to know to go from great looking digital images to great looking prints, but remember that resolution is no substitute for composition. You need strong composition as well as good resolution in order to produce an excellent print. So experiment a bit with your camera's quality settings, choose the one that's right for the photography you do, and let your compositional skills do the rest of the work.
Most people think this post is Awesome. What do you think?