Red pixels when shooting the night sky

Sightaridis

I am trying to make a time lapse video of the stars moving across the night sky, and I have done so, but on each frame there are certain fixed pixels which kinda ruin the whole timelapse.

Here is a single frame, these same pixels are in every image and thus stay stationary throughout my time lapse video. It is the full resolution.

http://img199.imageshack.us/img199/6355/img0116uj.jpg


Any ideas?

I was shooting large jpegs, ISO 800, 20 second shutter, f7.1
Canon EOS 450D, 18-55mm kit lens

oshead

It's a hot pixel on the sensor. Usually found in long exposures like yours. Nothing to worry about.

kjt

My bet would be on 'hot pixels'.

More info on them here.

zerohamster

They are indeed hot pixels, every sensor has millions of photosites that capture the light, each is 1 pixel of the image and there are always a few hot pixels. it would be nearly impossible to have none on a sensor when manufacturing so the manufacturers have a tolerance as to how many there can be on each sensor to pass quality checks.
they are more noticable during long exposure and are either green, blue or red due to the "bayar array" filter that seperates each photosite into 1 of the prime light colours (there are two times as many green photosites as red and blue because our eyes are roughly twice as sensitive to the green spectrum of light)

I dont use this myself but it seems like it might do the job and in batch
there is a free version there so its worth a shot.

http://www.lightningcube.com/hotpixelremover.htm

Edit: just noticed there are a good few more hot pixels in your photo, they are the blue dots you can see. hot pixels are easy to spot in long exposure with stars because they are stationary where as ther stars have a small motion trail.

Sightaridis

Thanks for the info fellas. Glad to hear it's nothing more serious. I'll give that program a try too.

Crispin

Aliens. Hot pixels are a myth invented by the government to trick us.

Shzm

I thought it was them blasted chinese lanterns

zerohamster

Yeah man! the government trying to trick us man....I know its aliens...*hushed tones* theyre following me...every pic I take they're there man...just watchin in the same place!:D :rolleyes:

Chorcai

zerohamster wrote: »

Yeah man! the government trying to trick us man....I know its aliens...*hushed tones* theyre following me...every pic I take they're there man...just watchin in the same place!:D :rolleyes:

I stocked up on tin foil the other day, have plenty to spare if you want some !

:pac:

melekalikimaka

kjt wrote: »

My bet would be on 'hot pixels'.

More info on them here.

http://www.youtube.com/watch?v=c-D9SPn1M0Y

i think the video explains it better

zerohamster

Haha lovely! spare some for my dog too, then out to the corn fields to find mel gibson, joaquin phoenix and a baseball bat hehe