|
Rob
ICNR is where the Canon 40D automatically takes “Dark Frames” after each light exposure.
When this is enabled (User sets “C.Fn II–1” to “2=On”) then the 40D will take a Dark for every exposure over 1 second.
So, when you take a 3 minute exposure of say, M83, the 40D will automatically begin a 3 minute “Dark” exposure (ICNR) as soon as the M83 light is completed. This effectively doubles your imaging time, i.e. 3 min M83 + 3 min Dark = 6 mins total.
On my SBIG ST7E, where the cooling temperature is regulated, I have the luxury of taking say, 10 x 3 minute lights of M83 consecutively, followed by say, 5 x 3 minute darks at the end of the imaging run as the chip is at the same temp throughout.
I think that Bert has investigated ICNR on the 5D fairly comprehensively and IIRC, his recommendation was to use ICNR rather than switch it off and try to apply separate Darks later on.
Cheers
Dennis
|