2 Lens focal length Calculation

[dracul]

http://gwidijanto.fcpages.com/2lens.xls

Is this for using 2 different projection lenses or is this a calculator for using fresnel lenses?
If its for projection lenses, for instance I have separate 2 327mm lenses by 18" and get a 24 inch FL lens now. Correct?
So the drawback to this is 18 inches bigger box....?

Also using the projector.xls calculator, my optimum lcd to lens distance is 12.87 inches the same as FL of my projection lens correct?

Advice is "use panel with FL equal to LCD to Lens distance or closed to to get maximum result"

Using the 2 fresnel system, I thought it was recommended to place the shorter FL fresnel first or infront of the lamp at 8.9"(using diylabs special fresnel split). However Lcd to lens distance is 12.87" and this cant be shorter because Lcd to lens distance cant be smaller than FL of projection lens.

 

[jcbklyny]

The shorter FL goes on the bottom whether your splitting fresnels or not. This increases the light gathering ability of the lens itself. The top fresnel should have a slightly longer FL then the projection lens. You want to flood the lens with light. So thats why people are getting better results splitting fresnels. The FL of the top fresnel is increased and more light floods the lens. (At the cost of a blurry image)