A lot of noise with low iso

[Photosformyson]

I thought I had understood iso, until I saw this picture. Granted, I was just messing around, trying to capture the moment (and not let him eat ALL of the marshmallows) but now I'm confused by the noise. What could I have done different?

This was shot at night, with lights on with my 7d. Iso 250, 1/160, f/2.2, no flash.

 

[bhphotography]

The noise typically comes from a lack of light. Iso does make a difference, but it all comes down to light quality. If the light is missing parts of the colour spectrum, there will be more noise

 

[gsgary]

With those settings indoors it must have been badly under exposed and if you try to make it brighter you get lots of noise, even cameras that are good at high ISO have to be expose properly

 

[inTempus]

Yup, I'm guessing you underexposed then bumped the exposure (brightness if you will) up in post. This will cause noise to become visible.

 

[Big Mike]

Yes, the real key to avoiding noise is to nail the exposure so that you don't have to adjust it in post...you especially want to avoid having to make it brighter, as that's really when the noise shows up.

If you can do this, you should be able to get fairly clean images up to 3200 etc.