| 6" Fresnel Lens Spotlight (Fresnel) The 6 inch, 750 watt Fresnel is a soft edged, variable beam instrument which is primarily used in the educational and community theatre. It is normally used on stage for area lights and general washes. The size of the pool of light is determined by the throw and the position of the focus knob: Spot to Flood. (Cost of an Altman 6" Fresnel with a 750w lamp: $ 138 at StageTechnology) |
| Focus | Diameter at 20' | Intensity with 750 watt lamp |
| Spot | 6' (MF=.3) | 230 fc @ 20' feet |
| Flood | 28' (MF=1.4) | 22 fc @ 20' feet |
| 8" Fresnel Lens Spotlight (Fresnel) The 8 inch, 1000 to 2000 watt Fresnel is a soft edged, variable beam lamp which provides a greater punch than its 6 inch brother. It is primarily used on stage for strong washes of side and back light or when the throw is too long for a 6 inch unit. The size of the pool of light is determined by the throw and the position of the focus knob: Spot to Flood. (Cost of an Altman 8" Fresnel with a 1000w lamp: $ 289 at StageTechnology) |
| Focus | Diameter at 30' | Intensity with 1000 watt lamp |
| Spot | 6' (MF=.2) | 189 fc @ 30' feet |
| Flood | 25' (MF=.83) | 22 fc @ 30' feet |
1. What is a Fresnel lens?
The Fresnel lens, developed in 1822 (for use in light houses) by Augustin Fresnel (1788-1827), is a less massive form of the more common plano-convex lens.
2. How does it differ from a plano-convex lens?
Augustin Fresnel reduced the mass of the plano-convex lens by converting the convex side of the lens into a series of concentric prismatic rings. From the front, a Fresnel lens looks like a bulls-eye. For more information go to answers.com
3. What are the two commonly available sizes of theatrical Fresnels?
6 inch and 8 inch
4. What range of lamps (wattage) does each use?
6 inch: 500 and 750 watt.
8 inch: 1000, 1500, and 2000 watt.
5. What is the field angle of a 6" Fresnel at spot focus? At flood focus?
Spot focus: 16°.
Flood focus: 70°.
6. How do you change a Fresnel from a spot to flood focus?
By sliding the focus knob from the back (spot position) of the light to the front (flood position) of the light.
7. How large a pool of light would be produced by a 6" Fresnel at spot focus with a 30' throw? At flood focus?
Spot: 9 feet.
Flood: 42 feet
Math for Spot Focus: 30 foot throw * .3 multiplication factor = 9 feet
8. How do you shape the pattern of light from a Fresnel?
The pattern of light from a Fresnel can be shaped with a barn door.
9. What device can be used to cut down the spill from a Fresnel?
The spill from a Fresnel can be reduced with a top hat or funnel.
10. What is a PARnel? How is it different from a Fresnel?
The PARNel is an ETC Source4 PAR with a "patented wave lens system." It is a newly created fixture with the flexability of a 6" fresnel and the performance of a Source4 PAR. Like the fresnel, the PARNel has a soft edge and a variable (25° to 45°) beam angle. It is normally used on stage for area lights and general washes. The size of the pool of light is determined by the throw and the position of the focus knob: Spot to Flood. (Cost of an Source4 PARNel with a 575w lamp: $ 243.00 at StageTechnology)
ETC Source4 PARnel
Focus Diameter at 20' Intensity with 575 watt lamp Spot 8.2' (MF=.41) 328 fc @ 20' feet Flood 15.6' (MF=.78) 81 fc @ 20' feet
11. In what mounting positions are Fresnels traditionally hung?
Fresnels are generally hung back stage and used as "area lights" on the First Electric or to provide soft edged washes of down and back light.