Another Great G7/CHDK Benefit!

Started Oct 28, 2007 | Discussions thread
Divalent Forum Member • Posts: 99
I tested myself in an S3. It makes sense now.

I tested 800 ISO at 1 sec and at 1/60 sec exposures, 4 shots each of the same scene, two each with "Noiser Reduction" ON and OFF. It clearly is noisier when the NR is ON at both exposures. (And other than worse noise, I saw no difference in the overall intensity or other difference.)

However, I also tested again at 1/60 sec exposure but additionally used the AUTO setting. In that test, I could see no significant difference between the AUTO and OFF settings, but (again) both were better than ON.

So in my tests, it was clear that setting the "NR" to OFF resulted in a lower noise level on the images compared to the ON setting. But it did not improve things compared to the AUTO setting if the image was taken at an exposure where the camera would not normally do the "NR" proceedure.

BTW, the label "noise reduction" is really a misnomer: what this parameter is referring to is the "dark frame" subtraction routine. The purpose of DF subtraction is to remove the time dependent signal on the sensor (a signal that generally is only significant with long exposures, although some individual pixels can be significantly worse than average). You would predict that the DF subtraction process should add noise (and in fact, it does, as everyones tests show), but at least in my S3, at a 1 second exposure it seems to do nothing but add noise.

Thus, setting this to OFF is probably best for most applications (and setting it to ON seems foolish), but for 98% of the shots we take (faster than 1/3 sec exposure), the OFF setting really provides no benefit over AUTO (the native camera mode without CHDK), since the DF subtraction won't be done anyway for those images.

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