i need to go as wide as possible without a very extreme barrel distortion, something in the neighborhood of a 16mm flat wide angle for 35mm.

I checked out the .3x century optics on a 20x lens very briefly once and i don't remember it being THAT distorted, and a 19mm equivalent would be sufficient but i own a century optics .6x adapter for the 20x and it appears that it is the same piece that is compatable with the 3x canon lense, is that correct? i believe that would give me a 15mm equivalent but how distorted is the image?

also, i'll be doing some shooting in the desert just before dawn to be used as night footage, so loss of light is an issue.

can the .6 adapter on the 3x lense be zoomed through?

thank you very much for any input.

-Jon

people are using wide angle only for one reason. The distance from the subject to the camera must be short while keeping large field of view.
Usually when the scene does not fit in the screen, you simply walk back.
In your case, filming in a desert should allow you to take as much distance is required to fit the scene in the screen without the need for a special wide adapter.
this will probably give a lot better take than forcing light to unnatural path with lenses.

i completely disagree, there are a number of reasons why people use wide angle lenses, the perspective for instance, a wider lens stretches the distance between near and far and a telephoto flattens it, watch citizen kane if you want to see the psychological effect of a short lense. it is not at all a case of getting more stuff in the frame from a shorter distance, that's just lazy camerawork.