Nik Software's Dfine is a powerful, flexible, and easy to use tool for reducing digital image noise. It does a great job right out of the box, but a custom profile for your camera can help you get even better results very easily. I recently created custom profiles for all of my cameras, and below I'll outline how I did it and even provide a link you can use to download my profiles for your own use. The cameras I profiled are:
Since each model of camera has unique noise characteristics, I decided to profile each camera separately. And, because noise increases as ISO rises, I created a profile for each ISO setting at 1-stop intervals. Finally, since cameras' noise levels are higher in some colors than others, I used a 24-patch Xrite Color Checker Passport rather than a simple gray card as reference.
So, I started by photographing the Passport with each camera at various ISO settings in indirect sunlight, slightly defocusing the lens to obscure any dust or surface imperfections and render each patch as an area of even tone. I then imported the photos into Aperture and set the RAW Fine Tuning sharpening and de-noise sliders to zero for each. Next, I opened each image into Dfine, selected "manual" for measuring method, and placed a measuring square over each patch. Like this:
I then clicked "Measure Noise" and saved the profile. Simple, really, though placing 24 squares on each of 6-8 photos (ISO 100, 200, etc.) for five cameras gave me time to listen to lots and lots of stand-up comedy. After all that work, I verified that it did, in fact, make a difference. The images below show results of auto versus custom profile noise reduction on a photo from a DMC-GX1 shot at ISO 12800. About half the patches showed the degree of improvement seen below, and the rest were better, but more subtly so. Overall, I think, a worthwhile effort.
With these profiles in place and the appropriate preference settings, Dfine will automatically apply the appropriate profile to images made with these cameras, giving great results with just one click.
If you have any of these camera models and would like to use my profiles with Dfine, feel free to download them here:
UPDATE 2014-10-27: I've added profiles for Panasonic DMC-G6 and DMC-GX7 cameras.