Digital Photography: Hot Pixels and Dead Sensors

Leave it to a wildfire to point out the flaws and imperfections in your pristine and shiny new digital camera. Before I get too deep in the subject of camera imperfections and how to correct them, please join me in a rousing rendition of Billy Ray Cyrus’ “Where Am I Going to Live When I Get Home?”

No, seriously, just a real quick word of thanks to all of the National Guard, Firefighters, New Mexico State Police, LAPD (that’s Los Alamos not Los Angeles… anybody needs a nightstick thumpin we know who to call… KIDDING!!!!), and all of the community, the lab and my employer for their support when you get booted out of your diggs (with good reason…).

And yes, thanks to all of the politicians (Gov. Martinez and all) doing what they can to get things done as well. Sen. Tom Udall, (D-NM) addressed evacuess at the Santa Claran Hotel on Tuesday, in describing the wildfire conditions, he said… “Well, you never are safe when you have such a dry situation, and you have fuel load and you have vicious winds like this,” said Senator Tom Udall, a New Mexico Democrat who visited evacuees at the Santa Claran Hotel Casino in Espanola. “When you combine all of those together, [it’s] very explosive.”. Just a word of advice, Senator Udall… When describing conditions at a nuclear research laboraty, the word “explosive” should probably be way down there on the list of preferred adjectives…

So, I noticed when I took a real close look at some of my night shots, these little tiny specks in the pictures. They looked like this.

See the bright dots on the screen. Those are not uncommon in digital cameras. They’re called “hot pixels”, “dead pixels”, etc. Hey, I didn’t pick the names…

What happens is for every dot on the sensor, the camera receives light and color information and translates that into a picture. Modern camera quality control standards do not allow for every single pixel on a camera’s sensor, (there’s 18 million in an 18 megapixel sensor), to be perfect, so…, a little post production, (editing), is called for.

Usually, there are just a few in the image and they become very apparent when photographing very dark backgrounds.

If the dots appear a particular color, the sensor is stuck in the position to register that color. See, the little “x” in the picture? That’s a dead pixel.

If you consult you camera user’s manual, they have a method for the camera running a self-test and figuring out where these dead pixels are, then correcting them. Is this something to worry about?

Not really, running you camera’s software that came with it can fix it, Adobe Photoshop CameraRaw fixes the problem automatically. In order for me to post this example it was actually easier to download a different program that would not correct the problem automatically, just to show you what they looked like.

I’m going to head out and try and get some more fire pictures tonight.

Hot pixels or dead pixels on your sensor? As long as the number is within reason, they’re not too big of a deal. Besides, if you get too many in one image, you can create your own constellations…


Update 6/29/11 11:00 am: Made it up to White Rock last night. The good news, no pictures to be taken other than a thick haze of smoke obscuring visibility. Had a milk and a Zero on the way back into Santa Fe. The milk tasted like Lapsang souchong. The fire crews have done an amazing job of keeping the fire away from town and keeping the canyons covered. Town meeting today with news of expectations, etc. The guards up on the hill are doing a great job. Morale on the hill is reasonable and the biggest imapct on the community so far has been the amount of distressed wildlife coming down from the mountains. More as I get it.