Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Useless...don't waste your money

I wear glasses and press against the viewfinder as hard as I can to help keep the shot stable (I shoot birds at 700mm). The first thing my friend and I did was to compare two identical lenses/cameras etc. - one with, one without, the extender.Result: - the image appeared the same size, and the extender slightly blurred the image. In other words - completely useless.