I frequently hear questions like this:

I want a 10 foot wide vinyl or canvas poster? Will my iPhone camera produce an acceptable image?

There are many rules of thumb when it comes to this question, and often these quick guidelines produce a result that is overly conservative.

The best answer that I’ve come across is in a formula that also factors in for viewing distance. It’s not difficult, but you’ll need to recall some basic algebra skills to use it.

The Guru’s Best Formula for Great Large Banner and Poster Prints:

(distance in inches)
1/((distance x 0.000291) / 2) = pixels per inch of final output (ppi)

So, if you’re viewing from 10 feet away (120 inches)

So, you will need 1/((120 x 0.000291) / 2) = 57.27 ppi for final size

That’s a total of 6874 pixels for a 10 foot wide poster. That’s a 20 megapixel or more photo, far in excess of most camera phones.

Most modern camera phones produce a 8 megapixel image: 3264 x 2448 pixels. That’s roughly half the pixel count needed for a 10 foot wide poster viewed from 10 feet away. Depending on your camera’s settings, the pixel count of the photos you export could go even lower.

Admittedly, there’s more to quality than pixels, but the above formula will get you the most “bang for the buck.”