It seems intuitive enough. More megapixels is better, right?
But, as with most things electronic, the magic number just seems to keep on growing… 2, 5, 8, 11, 15, 18, 21?!? How many megapixels do you really need?
Approximate Resolution of Various Output Types
One way to think about this question is to estimate how many pixels (and therefore the number of megapixels) it takes to effectively render a few different common output formats.
Facebook. Let’s say you want to share a picture over the Internet. If you’re on Facebook, the largest possible image size is 720 pixel x 720 pixels. That’s 921,600 pixels… or a whopping 0.9 megapixels.
Other Web Sharing. Let’s say you just want to share some pictures over the web and look at them on your computer. While the upper limit on the resolution will vary, it will be limited by the size/resolution of your monitor. My 19? flat panel and video card on my desktop support a resolution of 1440 x 900 pixels. That’s a total of 1,296,000 pixels, or 1.3 megapixels. Hmm… now we’re getting closer to modern times.
Basic 4×6 Print. Ok, let’s up the ante and contemplate a print product. Typical print resolution is 300 ppi (pixels per inch). That means that a 4 inch by 6 inch picture will require approximatley 1200 pixels by 1800 pixels. That’s 2,160,000 pixels, or a shade over 2 megapixels.
Large 8×10 Print. Want something bigger? How about a nice 8×10 print that can fit in a matted 11×14 frame. At 300 ppi, that requires 2400 x 3000 pixels. That’s 7.2 megapixels. Now we’ve actually entered the realm of modern cameras. But, still, most consumer level digital point and shoot cameras deliver at least 7 or 8 megapixels.
Uber-Large Poster Print (24 x 30 inches). And now for something obscene. Let’s make a really big poster print. At Costco, I can print an image at 24×30 inches for $8.99. That would require 7200 x 9000 pixels or 64,800,000 pixels. So, a full 300 ppi image would take, umm, 65 megapixels. Oops. They actually look pretty good at ~12-15 megapixels as long as you don’t hold your nose an inch from the picture.
In other words, pretty much every conceivable normal output format (from web images to an 8×10 print) requires less than 8 megapixels. If you’re a professional photographer creating movie posters, large print ads, or the like, you could probably benefit from a higher resolution. And there are some reasons why you’d like to have a little extra resolution to spare. But, while more is better, that doesn’t mean it’s necessary…
Food for Thought
In 2004, Canon’s flagship camera was the EOS 1D Mark II. That camera, near the top of the line of professional Canon dSLR, offered 8.2 megapixels. It’s successor, the EOS 1D Mark II also topped out at 8.2 megapixels, and the flagship line didn’t increase until the EOS-1D Mark III was introduced in 2007 with 10 megapixels.
Up until a few years ago, 8-10 megapixels was enough for professional photographers the world round. So, although today’s flagship camera offers 16 megapixels and the more recent 5D MK II offers 21 megapixels, these aren’t exactly necessary. It’s nice, but it’s something of a luxury, and often times it’s entirely unnecessary.
Does that mean you should turn away a high megapixel camera? No, not really… but you can find some few-years-old digital bodies in good used condition for a decent price. If there’s no other reason for you to choose the newer body, you can save yourself hundreds of dollars by buying a slightly less-than-modern camera that offers less-but-enough megapixels.