Oodles of Noise at 200ISO??

[littlenomad]

I have a 7d and was using my Sigma 50-150mm 2.8f as usual. I have a thing about tack sharp photos so have really worked on this and had no problems until this session.
I couldn't figure out why I couldn't get the usual tack sharp photos. I tried ramping up the ISO to 320 (shutterspeed 400) because I thought it was due to me not having had lunch yet (get the shakes a little in this case) but no matter what I did it was a mess. And surely at ISO 200 there shouldn't be this much grain either way?
Here are a couple of the photos...I just imported them into lightroom and did nothing else. Obviously I shoot in raw and I move my focus points around. Unless I somehow did manage to get the focus off...casting an eye on the tree in the background...but again how?
I also opened them in Irfanview and the same issue again.

Here is from another shoot (although slightly lower ISO and higher shutterspeed).
Or am I loosing my marbles?

 

[Derrel]

I see missed focus, and poor lens performance. The top shot is riddled with bad chromatic aberration...that strong magenta hazing around the tree bark...that is CA. There is not much depth of field at f/2.8. On the first shot, the face is missed, but the hair is in focus but it looks like the lens is just not up to snuff. In shot #2, her face is obviously not the focus subject, but rather the contrasty hair/background junction seems to be where the lens locked on--but the overall lens performance is poor. The CA is still there, but doesn't show up much due to the subject matter.

 

[unpopular]

Color temperature seems low. I'd imagine that this would be closer to 6500k than 5000k. If there are color corrections being done to overcome white balance miscorrection, this could be a source of noise.

If the scene was that cool, then I don't know.

 

[KmH]

Digital photos can't, and don't have grain.

They can have image noise, but as Derrel points out your issue is poor lens performance. There is minimal image noise in the photo you have posted.

Reviews of the Sigma 50-150mm f/2.8 II EX DC HSM show that many examples of the lens do not focus accurately using AF, and that when manually focused the lens is noticeably sharper at f/5.6 than it is at f/2.8. That lens is sharpest at f/5.6, and gets less sharp as apertures get smaller (f/8, f/11, etc).
It is common that many 'fast' lenses need to be stopped down a couple of stops before they can focus sharply.

Digital Camera Image Noise Concept and Types
Tutorials Sharpness
Camera Lens Quality MTF Resolution Contrast
Guide to Image Sharpening

Real World Image Sharpening with Adobe Photoshop, Camera Raw, and Lightroom (2nd Edition)
The Digital Negative: Raw Image Processing in Lightroom, Camera Raw, and Photoshop