Digital Camera Resolution: It’s Not The Dots

Overview of the scene - 8 MP image
Overview of the scene - 8 MP image

A rule of thumb for cameras is that more glass is better, so I’ve always been skeptical of those little bitty chips o’ glass in front of all those pocket-sized camera CCDs.

A while ago I took some shots with my Casio EX-Z850 at various resolutions, chopped out a chunk with some good detail from the middle of the images, and resized (cubic interpolation) the smaller ones to match the 8 MP image. The exposure was automagic: 1/200 sec at f/7.4. Zoomed as far as the optical zoom would go, hand-held ’cause at that shutter speed it’s OK, sharpness and contrast one click higher than the default.

As nearly as I can tell, there’s only a slight difference between 8 & 6 MP, enough to be noticeable at 4 MP, and it’s getting on toward icky at 2 MP. The picture isn’t any bigger because I wanted to preserve the actual dots in the 8 MP image.

Resolution Test - Shield
Resolution Test - Shield

Notice the weird color gradations in the shields with bright primary colors. This was hand-held, so the camera reached the same image conversion conclusions each time, starting with different physical pixels. A bit of rummaging turns up the Island Coffee Co logo at

Just to show that resolution doesn’t matter in real life, check out the snail. Zoomed all the way out, macro focus, 1/125 f/2.8 (wide open), hand held, resized as above.

Resolution Test Images: Snail

As nearly as I can tell, the 2 MP image is the only one that’s noticeably worse and it’s still just fine. The other three are different, but even the 2 MP one isn’t bad.

Moral of the story: lots o’ dots is good, but beyond a few MP it just doesn’t matter. I think 4 MP is the sweet spot, based on an entirely insufficient sample, with 8 MP if you’re planning tight cropping. Otherwise, save 2 MB per image: 8 MP -> 4-5 MB, 4 MP -> 2-3 MB.

The other High Truth: lots of light is a Good Thing. You get really crappy pictures when there’s not enough light, but it seems that’s where all the interesting stuff happens.

Update: Uploaded the PNG version of the shield resolution test, as the JPG was fairly crappy, plus 8 MP overviews of the scenes. The text is antialiased and looks awful when you zoom in, but the whole point is to show the actual dots produced by the camera: there aren’t that many dots for the letters.

Snail overview - 8 MP image
Snail overview - 8 MP image

One thought on “Digital Camera Resolution: It’s Not The Dots

Comments are closed.