I have a Tamron lense 18-250mmm for Canon. It does not focus with zoom use, iwith different Canon bodies , particularly with a focus on a light or low contrast point. Canon lenses do not seem to have this problem. What to do
Cameras - Tamron - 28-300mm f/3.5-6.3 DI XR for Canon
Answers & Comments
In low light situations, connect a speedlite flash to your body (e.g. 430EXII or 580EXII). These flashes emit a AF assist beam to assist focussing in low light situations.