Canon 1100D long exposure noise reduction

[williamnohair]

Hi

can anyone tell me what the advantage of shooting dark exposures is when the camera will do it for you? From listening to the shutter etc it seems to do exactly what you would do in DSS except its done immediately, and the processing doesn't seem to take that long. The only advantage I can come up with is that you get your lights quickly and then if the seeing changes for the worse you can get your darks without any hassle, however if you have a good night it doesn't (as far as I can tell) really matter.

Anyone with any thoughts on this?

Bill

[jgs001]

Bill, with short exposures, it's not so much of an issue, but you'll notice it far more when using long exposures... Basically, long exposure noise reduction, takes a dark immediately after each light and subtracts it. So if you shoot for 4 hours with the NR enabled, you actually only get 2 hours of exposure time. If you shoot darks, you get 4 hours of exposure time, and then capture some darks afterwards.

[JB80]

The length to process it in camera is one thing, it's definitely annoying if you are taking lots of lights to have to wait all that time again for the dark.

Also from what I have read is that DSS does a much better job at processing the darks than the camera as it creates an overall average of the noise as opposed to the single frame from the camera.

[williamnohair]

Thanks Guys

pretty much what I thought and so far yes have only done short exposures so haven't been that frustrated but I suppose if I ever get to take longer than two minutes I will end up switching it off. Unfortunately the area that I live in suffers from a deep red afterglow possibly from the M 25 or just street lighting so my optimum exposures so far have been (without a filter) 2 mins at 400 iso at F4. If I up the iso I get too much background interference and if I lower it I lose some detail.

But oh for a clear night!!!!