Add the 1.6X Tele-Converter to the front of your zoom lens to shift its focal range in the telephoto direction.
The perfect tool when it's inconvenient & dangerous & or even impossible to move as close to the subject as you'd like.
There is no appreciable light loss. Note that the Tele-Converter offers partial zooming & vignetting will occur at mid-range through full wide angle.
1lb 10oz (731g)
Angle of View
zoom, vignettes at wide angle