Using DX lens on a FX Body

I was wondering if DX lenses in body FX could be used without any problems. I installed Tokina 11-16mm PRO for Nikon D800. The vignetting effect is visible below 15mm, generally with this 16mm lens you can shoot without fear.

For example, night photography in a 16mm (post header), F8 aperture, ISO 100. At the aperture below F5, visible blur and problems with focusing on 30% of the frame. Below is an example on F9, the whole photo is sharp.

Conclusions:

In the case of wide-angle lenses below 15mm vignette visible, difficult to remove in a post-process. Below F5 a visible decrease in quality. The use of DX lenses together with body FX will be a temporary replacement for architectural and landscape photography.

Below examples on F9 and 16mm.