I have the occasional need for a wider lens than a 24 / 27 length and I am more than happy to use fully manual lens with if needs be a adapter, but not knowing the Nikon or Cannon offerings ,as I came from Pentax, I have no idea what to look for. I have looked at the Samyang range but they are either for crop bodies or in the case of the 14 T3.1.the lens hood is fixed and you can't mount filters. I have a Tammy 10-24 (pentax mount used with a adapter) but to avoid vignette it has to be used from 15 mm to 24 and the aperture closed down to I guess what is about about f8. Anything more closed down also results in heavy vignettes. Suggestions any one ?