Im used a 17-85 is lens on my 30d at iso 100 for a 30 second exposure. Why am I still getting noise? you can see it in the water and the sky. I tried using noise reduction in the pull down in photoshop but still get the noise. Thanx for the help.

 

Did you raise the exposure, levels, curves, or any other setting?

 

raised exposure 1/2 a stop

 

30 second exposure is the culprit here, I believe. With high ISO's, the system is effectively turning up the gain, so you get more noise. With lower ISO's on long exposures, you are storing the sensor output over a longer period of time, so any noise at all gets captured. Consider it like taking all the noise from a hundred 100ISO images and putting it all into one.

You might experiment with shutter speeds to find a sweet spot with lower noise but enough exposure. Or use a larger aperture.

 

That 30 second exposure might just be too long for your sensor.

 

there is a "custom function" that allows for long exposure noise compensation. look it up on your manual.

 

ok.. waiting for lunch to come around here you go

http://www.kenrockwell.com/canon/30d...-functions.htm

 

1/2 stop bump in exposure is a lot when capturing very low light levels. You're basically bumping pixels that aren't there.

 

what if i bumped the iso to 500 and use a shorter exposure? would i get a better photo with less noise?

 

your best bet is to always use the lowest ISO possible, smallest aperture and long exposure AND the long exposure noise reduction function on the camera.