Not wanting to impose my view. I only want to illustrate my point of view. This is a non-treated capture at 100% from a 350D with the Sigma 105 at 100%. I saved as jpg, best quality,  and had to crop, then save again as jpg, so there is inevitable loss. ISO 200, f 4,5 and t 1/400, with tripod. I never ever use a flash or any camera enhancements (unfortunately there are some that you cannot turn off in jpg shooting, which is one of the reasons why I now shoot RAW)

For my demands, this is sufficient. When tested in a laboratory on aberrations, chroma halo etc, there are certainly better lenses. But in real-life this difference in quality is only visible if you are a real master-photographer.

There are no Borg. All resistance is fertile.