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C.Fn II -1 – Long exposure noise reduction

This Custom Function lets you choose how noise reduction for long exposures is performed.

Setting 0 – the default, will not perform long exposure noise reduction.
Setting 1 – ‘Auto’, will perform noise reduction on exposures over 1sec if noise is detected.
Setting 2 – ‘On’, will perform noise reduction on all exposures with a shutter speed of 1sec or longer.

A form of dark field subtraction carries out noise reduction, so you may have to wait between shots while the camera captures another exposure of the same length as your set shutter speed. With a shutter speed of 10 minutes, it could take up to another 10 minutes to do the noise reduction. You will be able to continue shooting, as long as the burst indicator in the viewfinder shows ‘1’ or higher.