Diffusion is a thin heat treated material designed for softening and spreading light beams and reducing the contrast ratio between highlight areas. In essence diffusion is used to make the transition from bright areas to shadows softer and eliminate harsh shadow lines.
Types of diffusion are Polyester filters, frosts, and flexi-frosts. perforated diffusion grid cloths and spun materials.
Polyester filters: Spread the projected beam of light over the subject, some loss of light will possibly be seen. The greater the diffusion, the greater and more even the resultant spread of light. Shadows are reduced. Used to smooth out beam scallops when lighting cycloramas or in tight spaces.
Frosts: Frost is used for a variety of applications offering low to medium diffusion to a beam of light while maintaining the shape and beam centre.
Flexi-Frosts:Soft, quiet and pliable frosts which can be sewn for use on large frames. Waterproof, durable and thick makes them perfect for windy and rainy weather conditions./span>
White Diffusion (Complete over-all diffusion, eliminates beam edge and softens shadows)
Spuns (Overall diffusion, softens shadows, leaves beam intact)
Frosts (Softens beam edge, softens shadows, leaves beam intact)
Grids (Fabric diffusion ideal for outdoor use)
Silks (Spreads light uni-directionally along an axis)
When Using Diffusion Never Stack layers of diffusion material but always use the correct type of diffusion for the desired effect.
Intensity of diffusion is measured in Transmission value and Stop value.
Transmission value or "Y" is a percentage measurement of how much light intensity is reduced. For example a LEE 414 Highlight has a Y value of 39.6% which means that it is reducing the light intensity of 39.6% and allowing 60.4% of the light from the source to pass through to the subject.
Stop value correlates to the F-stop on the camera lens. Using the LEE 414 Highlight diffusion as an example. The 414 has a Stop value of 1-1/3.If you have a lighted scene and your lens F-stop is at F8 then after placing the 414 diffusion over the light you will need to open the lens to an F-stop of 5.6 to have close to the same light brightness in the video imagery.
LIGHT LOSS FOR COMMON LEE DIFFUSION:
White Diffusion "216": 1 1/2 stops
1/2 White Diffusion "250": 3/4 stop
1/4 White Diffusion "251": 1/3 stop
1/8 White Diffusion "252": 1/4 stop
Opal "410": 1/2 stop
Light Opal Frost "420": 1/4 stop
Hampshire Frost "253": 1/4 stop
Heavy Frost "129": 2 stops
Grid Cloth "430" or Silent Grid Cloth: 2 1/2 stops
Light Grid Cloth "432" or Silent Light Grid: 2 stops
1/4 Grid Cloth "434" or Silent 1/4 Grid: 1 stop
Full Tough Spun "214": 2 1/2 stops
1/2 Tough Spun "215": 1 1/2 stops
1/4 Tough Spun "229": 3/4 stop
Watch the video in full screen to view the subtle differences in the types of Lee Diffusion.
Other Lee Filters informational videos may be viewed on YouTube by clicking here.