Photoshop Adding Noise to Photos Suddenly

Question

Hi! I am hoping someone can help me with this. I have been using Photoshop for years. Within the past month or so, Photoshop CS6 has been adding noise to my photos after saving. This has never happened before. This is my process: I shoot in raw + jpeg, open the raw file in PS CS6, tweak it to my liking, run an action or two, and save (baseline optimized) as a jpeg. When I open the new file on my computer in Windows Picture Viewer (default program on Windows 8) there is a crazy amount of noise - noise that was not there at 100% in Photoshop. When I open in Windows Photo Gallery, there is still noise, albeit slightly less than in the default photo app. In Faststone, there is no noise - so I thought this was simply a Windows issue. However, after some troubleshooting I realized it is not a Windows error. Going back through photos I processed anywhere from 3 months to a year ago, there is no noise when I open with either program. I save most of my raw and psd files, so I went back to a few raw files whose jpegs did not have this issue, and attempted to resave as a test. They open fine, no grain. I thought perhaps it was a camera issue of some sort, however, the raw and jpegs that are not processed through PS show up perfectly fine, no grain. Also, it isn't an entirely consistent error, as maybe 5% of the photos do not have the noise after saving. The only fix I found was to lower my DPI - 150 did the trick, 72 was even better. Although I don't see my clients printing any larger than 11x14, I do promise them high res photos, so if it's possible they can print larger, I would like them to have that option.  I am at a complete loss as to why this is suddenly happening. If anyone has any insight I would be forever grateful!
Edit: I figured out that this is only happening with high ISO photos. Obviously, I understand high ISO=more chance of noise. What I am having a hard time understanding is that there is no noise in the JPEG SOOC or in the raw file in PS CS6 zoomed in @ 100%. If it wasn't there in the first place, why is it there now?

Answer 1

Thanks for your reply!
RAW files at higher ISO's (2500-3200) open in Photoshop and zoomed in at 100% look fine, with minimal noise. After saving in PS as a JPEG and opening in the Windows 8 Photo app or Windows Photo Viewer, they appear with terrible noise. In Faststone they do not have this noise. The only adjustments to size I do on my images are cropping to either 4x6 or 11x14 proportions depending on the photo. When I realized lowering the resolution was helping tremendously with my situation, I sized down to 150dpi and 72dpi, depending on the image, with resembling.
Older files and lower ISO files recently shot do not have this issue.
I shoot with a 5D MK II.