How many megapixels do you need?

One thing I've been getting interested in lately is photography. I have an Olympus C-50zoom, which is a little 5 megapixel "point-and-shoot" camera, and I recently joined a local online photography group (PinoyPhotography.org), so I can practice and get feedback on my pictures. (You can check out my pictures at online at http://hartsord.photo.net.ph/ )

The problem that I have with pinoyphotography.org is that while almost everybody there has a lot of passion for photography, most of them have passions (and pockets) big enough to drive them to get digital slr cameras. While I do enjoy photography, my passion is not yet enough to make me get a dslr with my budget. I'll continue to hone my skills with my p&s for now.

Which brings me to the question: how much camera do you really need? Nowadays, the rage is to have cellphones with cameras, and I consider myself a bit of a stubborn dinosaur because I still stick with my trusty Nokia 6100 (no camera) - I don't need a camera phone, because I get much better pictures from my digicam. Some readily available phones are now pushing 2 megapixels, but that's still a far cry from my 5 mp camera.

So does that mean that more megapixels are better? I wouldn't say that outright, because it really depends on the user. What do you intend to with the images you get? Is it only for web or computer display? What size prints do you plan to make? Are you a stickler for the details, or are you happy if you can recognize your grandmother's face in your picture? These questions are important to consider when you're trying to choose a camera that will fit your style, at least in terms of megapixels.

Generally speaking, what matters for most uses is not exactly the megapixel rating of a picture, but the DPI rating. DPI stands for "dots per inch," and for most computer screens or web use, 72 or 96 dpi is good enough already, while for printing, 200 dpi is already good, and 300 dpi will give you very good results. What this means is that to get a good picture to be printed at 4" by 6", your picture dimensions in pixels should be ( 4" x 300dpi = 1,200pixels ) by ( 6" x 300dpi = 1,800pixels ) or a 1200x1800 picture, as a minimum.

Note that most cameras take pictures in a 3:4 ratio (e.g. 480x640), so you have to allow for this cropping to get your 4:6 (or 2:3) print. Since a 3:4 pic is taller than a 2:3 print, we can leave the width pixels as is, and compute the height needed for our 1800pixel wide picture, which is ( 1800 / 4 * 3 = 1,350pixels ), giving us a minimum camera shot size of 1350x1800. To convert this to megapixels, just multiply the width by the height, and you get ( 1350 x 1800 ) or 2.3 million pixels or 2.3 megapixels for a very good print.

Or, if you don't like doing the math, you can forget all this and just refer to the table below:


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