multiple exposures to reduce noise?

[nakedyak]

I've heard of people taking multiple exposures at night to reduce noise. How does this work? Is it something you can do in photoshop? I want to get as much detail as possible out of my pictures with the least amount of noise. I have a 10d, and i dont think it can do that extra dark frame that subtracts from the regular one to reduce noise. Thanks

 

[Mohain]

I don't know about multiple exposures but to try to reduce noise on night shots you should expose to the right.

Cheers,

Mohain.

 

[markc]

The basic idea is to put the lens cap on and take a "dark frame". Just shoot using the same aperture/shutter/ISO that the original was taken in. This should be done soon after, not the next day, so that the temperature is the same, etc.

In Photoshop, copy the darkframe over the original as a layer (shift+drag to keep alignment if you do it with the mouse). Change the layer mode to "difference". This should remove the parts that are the same (the noise). I haven't tried it myself.

 

[Unimaxium]

There's also the technique to take multiple shots of the same scene and then stack them together in Photoshop. I know this is done often in astrophotography. PlasticSpanner should probably know more information about this technique.

 

[nakedyak]

Thanks for the advice. I was looking for an answer more along the lines of Unimaxum's, but i'll try all of them.