fresnel FL for collecting light

[ShagMan]

I have a question... why would you ever use anything but a short FL fresnel to collect light from your lamp? It would collect a larger arc of light (be brighter) rather than a long FL, which only collects a shorter arc. Even if you have a loooong front FL for a long-throw lense, you'd still want a shorter fresnel to collect the largest light arc.

Is my logic off there?

 

[Me2!]

What you are saying is correct.

The only reason for a longer fl from the lamp is if your reflector sends the light through a narrower angle. Then you have to match the fl to that.