3 USE FILTERS AND A POLARIZER Graduated
neutral-density filters and a high-quality polarizer can be effective in increasing dynamic range and saturation while reducing glare.
Red lenses are featured on LT, with RS, SS and ZL1 featuring dark-tinted
neutral-density (clear) lenses.
Although a
neutral-density filter will give excellent results, O'Meara prefers to use a blue (Wratten #47) filter that selectively attenuates the planet's ruddy glow.
The control group was on the same treatment schedule, but with light boxes that had been modified through the use of a
neutral-density gel filter to provide a dose of just 100 lux instead of the 10,000 lux at a distance of 1 m from the light source to the cornea generated by the active therapy light box.
Your review didn't separate sunglasses that filter all parts of the visual spectrum equally (known as
neutral-density filtration, which are always grey lenses) from those that claim to enhance visual perception.
Light intensity was regulated with fixed
neutral-density filters (Oriel Corporation) and measured with a radiometer (Model 550; EG & E, Inc.).
The
neutral-density filter rings are attached directly to the objective for easy exchange when brightness adjustment is necessary.
One of the filter-wheel positions held a
neutral-density filter; the other seven positions each held two filters: a neutraldensity filter and a bandpass filter.
Because the specular reflection from a pearlescent pigment is so much greater than the reflection from a BaS[O.sub.4] plate, a 10%
neutral-density filter was placed in the beam incident on the sample for measurements made at -15/15.