ISO, and You?
After several nights of shooting with my Nikon
Coolpix 4500 I started to notice a trend in low-light situations:
there seemed to be a high amount of noise in many of the pictures.
A quick look at the manual showed that this is a known problem
during extended exposures, but it turns out the ISO
setting has a lot to do with noise as well. Digital Photography Review has a good explanation of why this happens.
I took some sample images to compare noise at four ISO settings:
ISO 100, ISO 200, ISO 400, and ISO 800. These shots used automatic
sharpening, automatic contrast, and incandescent white balance
adjustment. ISO, exposure time, and noise reduction (NR) state are
shown below the image.
Ever-increasing amounts of noise can be seen as we move from ISO 100 to ISO 800. Quality on ISO 200 is acceptable to my eyes, with slight amounts of noise visible in areas of solid color.
For comparison, I reshot ISO 100 and ISO 200 with noise reduction
enabled. ISO 400 and ISO 800 were shot at faster than 1/4s, which
automatically disables NR.
Both shots appear identical to the ISO 100 image with NR disabled. Looks like I'll be relying on long exposure times instead of unnaturally high ISO settings. (Initial testing shows that a high ISO is much more damaging than a long exposure time. I can shoot an 8" exposure without noticible noise.)