how can i predict traffic levels for my niche?

let's say im doing a site on dslr camera lenses (actually im doing it)

there are as many keywords as there are lenses (300 +) and more.

i know its a very saturated niche, but i am an expert in the field and i want to concentrate my efforts on it.


how would you calculate approx. traffic levels for a given keyword if i hit 1 page of google? from there its easy to calculate the earnings.

thanks

Thats very hard to estimate. You can use adwords to get a rough estimate of monthly traffic from keywords if that helps.