Cutting Fresnel to Size Changes Focal Length ?

[dracul]

I have a normal ohp size unsplit fresnel. I want to use it for a psone lcd. The 150watt hqi is going to be dim I`m pretty sure.

If I cut the fresnel down to say 7x7 inches does this get me any more light passing through the lcd? What does it do exactly?

 

[Longwing]

As I understand it, cutting your Fresnel lens does not change the focal length.

I honestly cannot talk about the brightness though, as any guesses I made would be pure theory.