7d with Tamaron 17-50 Focuse and Grain

[SeaGrizzly]

Ok so I am pretty new to this but I seem to be having a hard time focusing with my 7d and this new Tamaron lense. Shots that I think are in great focus turn out with lots of noise even at 200iso. I didn't seem to have this issue with my kit 18-135. On the flip side 1 out of say 40 shots is crystal clear and in focus. What could be going on, could I just not be used to shooting at a more open lens? Why is it so hard to focus with this lens? Also it seems to get worse with less light, and that is a bummer because its pretty much why I bought the lens.

Edit: I decided to do some test shots and at the same F2.8 and 1/8th exposure I see that the Tamaron is way out of focus and the 50mm prime is clear as a bell. Both were shot from a tripod with a 2 second delay.

[ishootRAW]

Try using AF-macro adjust. It sounds like the lens is front/back focusing. Not sure about the grain. Sample shots?

[SeaGrizzly]

I was trying to upload some samples but they were really big because they were raw. I guess I can just crop out a section and upload that. How would I tell if the lens is front/back focusing, I actually am not sure what that means but heading to google to figure that out.

[oldwolf]

Don't crop the images. Post images or links to them from both lens along with EXIF data for both so we can analyze it and possibly come up with an answer for you.

[SeaGrizzly]

I am going to do another test today with some better light and a remote trigger to verify that I am not doing anything stupid and I will upload them.