Megapixels – Myths, Printing, and File Sizes Oh My!

That whole megapixel thing. Let’s talk about this for a moment… First we need to establish that most digital SLRs have APS-C sized sensors in them. They don’t vary more than a millimeter or two from each other – whether they come from Canon, Nikon (which is really Sony), Sony, Pentax, etc. They’re all about 23mm x 16mm – or in that ballpark. A full-frame sensor is the same basic size as a frame of 35mm film – 36mm x 24mm. There are other sensor sizes – the new Four Thirds format, the nearly tiny sizes of sensors in point-and-shoot cameras (about the size of your thumbnail) but for this discussion, let’s just assume the standard APS-C size. Now onto that sensor you place pixels. Mega numbers of pixels. My old Nikon D70 had 6.1 MP – or 6.1 million little collectors of light. My D300 has about 12.3 MP – on the same-sized sensor. What gives? How is my D300 so much better at higher ISOs? The quality of the pixels on the D300 is – in valley speak – like way more awesome dood! Also – the quality of the image processor in my D300 is similarly better. (If you want to read a very deep and head-scratching article on pixel quality – well click the link – but you’ve been warned). Even though we’ve doubled the pixel density, we’re still coming out ahead. BUT… the myth…

The number of pixels on the sensor isn’t the only thing to consider. You have to consider the quality as well. The Nikon D3 full-frame sensor with 12.1MP performs as well or better then the Canon 1Ds Mk III with 21.1 MP. The quality of the pixels wins out. The myth is that if there are more megapixels – well then obviously (dood!) that’s better. Sometimes more pixels just doesn’t help you. Sometimes it does. Pixels help you in two ways: 1) Printing and 2) Cropping. Let’s look at the second one first. If you crop from a starting point of more pixels, you’ll have more pixels left over. That’s good but we will always encourage you to get the best shot in-camera and avoid cropping if you can. The printing argument is important – but it comes down to how big you want to print and how good you need that print to look.

The guys at design215.com have one of the best “one page” explanations of the megapixel vs. printing story. When you check out this page all your questions – literally all of them – will be answered. Okay – maybe not all – but lots and lots of your questions will be answered. When you’re done getting that read – go read this – a handy printing guide that finishes the story.

And while you’re at it – check out this great example of digital file sizes from the design215 gang. It’s a pretty decent example of why your image files end up the way they do and let’s you figure out why things turn out the way they do.