Camera filters and its uses
Camera filters are a piece of equipment that Cinematographers often use to modify the light reaching the film to achieve a special effect or to improve the quality of image being recorded. Filters can be a square or oblong shape mounted in a holder accessory, or, more commonly, a glass or plastic disk with a metal or plastic ring frame, which can be screwed in front of or clipped onto the lens. Most behind-the-lens filters are made of a plastic gel-type material and must be handled carefully.
Conversion filters may also be referred to as color-correction filters. These filters are used to convert one color temperature to another. There are two different types of color balance for film; daylight and tungsten. The two basic types of conversion filters are:
The 85 filter is orange or amber in color. This filter is used to correct the color temperature while using tungsten-balanced film in daylight. It converts the daylight color temperature to the color temperature of tungsten light to match the color balance of the film stock.
The 80A filter is blue in color. This filter is used to correct the color temperature while using daylight-balanced film in tungsten light. It converts the tungsten color temperature of the lights to the color temperature of daylight to match the color balance of the film stock.
Neutral Density Filters
Neutral Density Filters are used to reduce the amount of light entering the lens or to reduce the depth of field for the shot. Neutral density filters are usually abbreviated ND filter.
Polarizing filter reduces glare or reflections from shiny, nonmetallic surfaces. Polarizers take light that is traveling in many directions and causes it to travel in only one direction; to achieve this you may have to rotate the filter and look through the viewfinder until you either remove or minimize the reflections.
Any filter that combines two or more filters into one filter is called a combination filter. The most common practice are those that combine an 85 with the series of ND filters to get 85ND3 85ND6 and 85ND9.
Optical flat is an optically corrected, clear piece of glass that may be placed in front of the lens to protect the lens from wind, dirt or dust.
Diffusion filters are used to soften the image or look of the picture. These filters contains a ripple surface, which prevents light from focusing sharply. Some of the most commonly used diffusion filters are Tiffin Diffusion, Harrison & Harrision Diffusion, Black Dot Texture Screen, Black Pro-Mist, White Pro-Mist, Black Diffusion, Gold diffusion, Soft/FX, Soft Net, Net, Supa-Frost, and Classic Soft.
Fog and Double Fog Filters
Fog filters are used to simulate the effect of natural fog which causes lights to glow and flare. The soft glow can be used to make lighting more visible, make it better felt by the viewer, however, the effect of a strong natural fog is not produced accurately by Fog filters.
Double Fog filter gives you a more natural like fog effect with the objects in the frame still looking sharp and in focus.
Contrast Control Filters
Low Contrast filters create a small amount of “localized” flare near highlight areas within the image. This reduces contrast by lightening nearby shadow areas, leaving highlights almost unchanged.
Soft Contrast filters include a light absorbing element in the filter which, without exposure compensation, will reduce contrast by also darkening highlights.
Ultra Contrast filter uses the surrounding ambient light, not just light in the image area, to evenly lighten shadows throughout.
When the sun moves through the sky, the color temperature of its light changes. So as to compensate this, the DP may use a coral filter to give the scene a slight warmer look.Coral filters are a range of graded filters of a color similar to an 85 conversion filter. From light to heavy, any effect from basic correction to warmer or cooler than “normal” is possible.
Enhancing filter are used to create brighter reds, oranges, and rust browns while filming outdoors. The effect is to increase the color saturation intensity of certain brown, orange, and reddish objects by eliminating the muddy tones and maximizing the crimson and scarlet components. Its most frequent use is for obtaining strongly saturated fall foliage. The effect is minimal on objects of other colors.
Graduated filters are used to alter a portion of the frame with a specific filter, while remaining the half is clear. We may use a neutral density grad or a coral grad for certain effects, a blue grad to brighten a blue sky without effecting other portions of the scene.
Some of the filter manufacturers are Tiffen, Harrison & Harrison, Mitchell, Schneider Optics, Formatt Filters, Wilson Film Services and Fries Engineering.