Originally posted by Sandy Hancock with the K-1) the image is clearly unacceptable until at least 14mm
If you look at the rings you can see what is caused by the hood. Dremlin away the hood will help, but not entirely cure the 10-17mm in the wide end.
Personally I plan to use the APS-C lenses Samyang 8mm f/3,5 CSII (the one with removable hood) and Sigma 18-35mm f/1,8 in FF mode, and crop in PP when necessary. Although in most cases I cant use the full frame, I will have more freedom of choice compared to APS-C mode. Freedom to choose other aspect ratios then 3:2 and other crop factors. I think I will get about 20-25 Mp out of most cases, as oppose to 15 Mp in APS-C mode.
With some APS-C lenses without hood, I will be able to take APS-C images in portrait orientation, while holding the camera in a more comfortable landscape orientation.