I was editing a few ISO 100 photos in Camera Raw 5.0. After editing a few I had to switch to a machine using Camera Raw 6.0. After loading my photos, I notices a very LARGE amount of noise. I can't seem to reduce the noise with the noise reduction tool, however when I adjust any of the HSL / Grayscale sliders the noise completely goes away while holding it. Any ideas? I am using CR2 files.
I seem to remember that they changed the noise and sharpening process in ACR 5.7. Previously, there was some default noise reduction affecting sharpness, and they removed this in 5.7 onwards.
If it's this, you'll see more noise, but your images will be slightly sharper. You may want to add some noise reduction to compensate.
If it's not this, then I don't know what you're seeing.
No one should be using the original release 5.0 or 6.0 versions of ACR. Update the plug-ins first of all, then post back.