What is the difference between a wide angle lens and a wide angle doubler lens?

Question

What is the difference between a wide angle lens and a wide angle doubler lens?

Answer 1

A wide angle lens is what photographers use for shooting landscapes and architectural images.  The sizes you will find for current DSLR's are from 10 mm to about 18 mm

A wide angle doubler sounds like an after market "flim-flam" lens adapter.  If you take the name at its word, it either doubles the lenses length so you no longer have a wide angle lens or it halves the length of the lens to make is wider (making a 18 mm into a 9 mm ... highly doubtful)