Originally Posted by M_Six
Of course moving objects will be a no-no in this mode.
Actually, if I understand correctly, the second exposure is taken with the mirror down so that the second exposure only shows noise, if anything. The second exposure is subtracted from the first exposure to remove the noise from the first.
It works great for long, night exposures, except a 30-sec. exposures turns into a 60-second exposure.
Our first night, the stars were bright.
, on Flickr
There was a light breeze, so the trees aren't as sharp as I'd hoped.