Dead pixels?

BeemerChef

Suddenly at around 800 ISO, night time, I am seeing some... dead pixels?
They are just bright pixels, maybe half a dozen...
Not familiar with this as it has never happened before.
Afraid to ask... what do you think? Is it fixable or? I very rarely take night shots...
This is on a spare 5D Canon...

Be well... Thank you.

Ara & Spirit

Richard

BeemerChef wrote:

Suddenly at around 800 ISO, night time, I am seeing some... dead pixels?
They are just bright pixels, maybe half a dozen...
Not familiar with this as it has never happened before.
Afraid to ask... what do you think? Is it fixable or? I very rarely take night shots...
This is on a spare 5D Canon...

Be well... Thank you.

Ara & Spirit

Post a sample, full sized.

BeemerChef

Richard wrote:

Post a sample, full sized.

This is going to be huge!... They are not stars... There was only the moon, venus and jupiter when I shot that...



Thanks... ISO 1000 f4

Richard

Hmmm...those sure do look like stars to me. Your camera might be more sensitive than your eyes, especially on a long exposure.

One way to test for dead (or stuck) pixels is to shoot a few dark frames with a lens cap on. If you get spots consistently in the same place, then you may have a sensor problem.

jogle

there are a few single hot pixels in there but you always get them with this kind of long exposure. make sure you have the long exposure noise reduction turned on in your camera. But there are plenty of stars too all the ones that have a slightly elongated shape of a soft edge are stars.

davidweaver

Stars. About a 20-30 second exposure?

Robinivich

As has been said, most of those are stars. A typical hot or dead pixel will show up as a single, maxed out pinprick of light, that only blurs slightly into neighboring pixels, and usually is coloured, because each pixel on this camera is either red, green or blue. Red and blue seem most common (I believe) because you have twice as many green pixels, they always have a "neighbour" to double check their results. If this is news, http://www.dpreview.com/learn/?/Glossary/Camera_System/color_filter_array_01.htm is an excellent link to help explain.

If you do have an issue with stuck pixels, canon has a custom function termed "long exposure noise reduction" in most of its cameras that basically takes a second picture immediately after the actual shot, that is the same shutter speed and sensitivity, but without opening the shutter, this way it can calculate which pixels are stuck (any pixel that reports light in the second exposure) and "subtract" them from the image. Persistently stuck ones that drive you crazy can be programmed out by a technician fairly easily, but I don't see a serious problem here.

I don't have any experience with the 5d (I wish) but this looks like typical results noise-wise for a long, high ISO exposure (I get F4, 3.2s ISO 1000 from the exif). You'd probably have had better luck on visible noise by selecting ISO 100 and a 30 second or so exposure in future (I know, sounds weird)