How many megapixels is a billboard?

It's always cool to see my photos out in the wild and also blown up BIG!

Many of my students ask me how many megapixels their cameras need to be because they want to print their images really big. As big as a billboard like this?!

It's a common misconception that you need a lot of resolution and megapixels to print large images. And it can be helpful if you're printing for a gallery exhibit or your home BUT the actual resolution required is actually more dependant on how far away the viewer is from the image.

Billboards are actually quite low resolution because you view them from so far away that it doesn't need fine detail for your brain to fill in the blanks. Like when I shot images to be printed on 18-wheeler trucks, they actually wanted lower resolution images so they didn't waste as much ink or vinyl on the final wrap! No one looks at an 18 wheeler from 4 feet away; they look at it on the road 20, 30, 40 feet away. It's doesn't need extreme detail.

Most people print 8x10s for their house. Take a look at the second image for a resolution calculator where you are viewing an 8x10 from 2 ft away (arms length). You only need 1.6 megapixels. So your 24mp camera is already completely overkill.

My recommendation is this... If you're just printing for your house and not larger than poster size, 12 megapixels is probably already enough and no one will be able to tell the difference. Stop buying more gear you don't need. Megapixels is just a marketing gimmick. :P