Q5 in a 20mm reflector vs aspheric

[Packhorse]

After seeing LED Zeplins latest mag conversion I am now contemplating building a mixed emitter Mag.

I already have 2 P7s and MCR20 lenses to give a nice flood beam.

I also want to have 2 Q5's for a tight spot but am unsure how to do it so any opinions are welcome. My aim is to have as tight a spot and as bright as possible.

I intend to be able to switch on either the 2 P7s or the 2 Q5s or both for use as a dive light. A tight spot is very useful for signalling to my buddy while the flood is good for general lighting.
My other dive light is a single P7 with 50mm reflector which gives a nice spot but lacks raw power.

The MCR20 seems to give a nice spot with the Q5 but is there a better reflector?

What about aspheric? I have not used one before and am wondering if they will give me a better spot. Since they must be mounted a certain distance from the LED does this mean the LED will lose the light from the side? Does this make much of a difference?
Im limited to 20mm in diameter or less. Can anyone recommend a good aspheric lens to use? Can I use an aspheric this small with a P7 or is it too small?

All opinions are welcome.

 

[Holzleim]

If you look at the link in my Signature you can see what can be achieved with a 17mm aspheric. A 20mm with appropriate (back-)focal length would do slightly better.
But much easier in handling will be usage of good TIR optics (20mm). Ra mentioned that (in theory) a TIR optic will have the same throw ability like an each (diameter) sized aspheric. http://www.candlepowerforums.com/vb/showthread.php?t=186096

However, I was very astonished about the light intensity I achieved with my 17mm lens.

 

[Packhorse]

Nice job on that Holzleim. What is the focal length of the lens?

So out of these 2 lenses which would be better?
I am assuming that a shorter focal length would capture more light from the LED. Is this correct?
Would a longer focal length give a tighter spot?
21mm*7.3mm Acrylic Lens
20mm*4.2mm Acrylic Lens - 25mm Focal Length

 

[Holzleim]

The plate the LED is mounted on is about 8-9mm away from the back of the lens. So it capture the light the XR-E emits in an angle of 90 degree.

Regarding the lenses you mentioned the second one has a far too long focal length, it would not capture much light from the LED. On the first one I didn't find the focal length mentioned.

To use a lens with a CREE XR-E one could say in general:
The lens should have a (back-) focal length of about half the diameter. In this case you capture light of ~90degree.


But coming back to your desired system: In such an multi-emitter setup TIR optics would be much better to handle than lenses, because they normally comes with holders than make it easy to place the TIR optic is right position. Perhasp one of these :http://www.fraensrl.com/prodinfo.html