Thursday, September 27, 2007

Canon 40D Night Time Exposure Tests: Part Two

As a follow up to last week's post about long exposures with the Canon 40D, last night I shot a pair of 9-minute exposures (f/9.5 at ISO 200) to compare the effect of in-camera noise reduction.

(9 minutes, f/9.5 ISO 200. Read below to see the 100% crops)

In a nutshell, in-camera noise reduction does a wonderful job of reducing sensor noise on long exposures. It works by immediately repeating your shot, but it turns the sensor on and keeps the shutter closed. This creates a "dark frame", which is electronically subtracted from the original image to produce a noise-free image. The disadvantage is that it locks up your camera for a period of time equal to the duration of the original image.

Here is the full image. You can see 100% crops of the shot without in-camera noise reduction here and here. You can see 100% crops of an almost-identical shot taken with in-camera noise reduction here and here.

2 Comments:

Blogger Delson said...

It looks like day light to me, but i keep wondering How did you manage not to overexpose the pic even with a 9 min exposure.
Great blog, and nice topic you work on Mr Frazer

rgds
www.delsonclicks.blogspot.com

8:35 AM  
Blogger Andy Frazer said...

Delson,

Thanks for your comments.

The shot took 9 minutes to expose because 1). the only light source is the full moon, and 2). I shot it at f/9.5. If you look closely at the sky you'll see the star trails.

Andy

8:25 PM  

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