Long exposure noise

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SamHH

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I understand that the heating of a digital sensor can create extra noise in long exposures. With that in mind, is it still best to use the lowest ISO setting, or would it be better use a higher ISO to get a shorter exposure?

Also, how effective is the long exposure noise reduction setting? Worth using?

Thanks
 
Generally speaking it is best to use the lowest ISO you can, but if circumstances demand a particular shutter speed you may have no choice and need to bump it up.

Camera models vary in how well they handle noise. I never turn on NR, but use processing software to deal with it if it is an issue.

If you mention what camera you are using someone will be able to say how effective the NR function is.
 
Thanks for the reply.

I'm talking about exposures between 30 seconds and ten minutes, so it's not a case of 'circumstances demanding a particular shutter speed'; I can use whatever shutter speed I need. My question is what will result in the least noise: say, an exposure of four minutes at ISO 100 or one minute at ISO 400? The camera is a Canon 30D.
 
Best thing to do would be for you to take a couple of shots and see which gives the results most pleasing to you. I would expect the shorter exposure at a higher ISO to have slightly less noise but high ISO noise can be different to long exposure noise.

In camera long exposure NR is quite effective on my D70 BUT it ties the camera up for a period the same length as the original exposure while it does the noise reference dark exposure, so not ideal if you want to shoot several exposures in a row.
 
No experience of Canon but plenty experience with long exposures. I can't for a moment imagine you'll have less noise with a higher ISO shorter exposure. Assuming the image is correctly exposed in the first place I'd bet on lower noise with lower ISO every time.
 
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