CAMERA FILTERS By Ira Tiffen © Ira Tiffen THE TIFFEN COMPANY HAUPPAUGE, NEW YORK
CAMERA FILTERS by Ira Tiffen INTRODUCTION Camera filters are transparent or translucent optical elements that alter the properties of light entering the camera lens for the purpose of improving the image being recorded. Filters can affect contrast, sharpness, highlight flare, color, and light intensity, either individually, or in various combinations. They can also create a variety of "special effects.
difference in the readings is the compensation needed for that filter. You could also use a spot meter, reading the same bright patch, with similar results. There are some exceptions to this depending on the filter color, the meter sensitivity, and the target color, but this is often better than taking a guess. Filter Grades Many filter types are available in a range of "grades" of differing strengths. This allows the extent of the effect to be tailored to suit various situations.
When it is desirable to maintain a particular lens opening for sharpness or depth-offield purposes, or simply to obtain proper exposure when confronted with too much light intensity, use a neutral density (ND) filter. This will absorb light evenly throughout the visible spectrum, effectively altering exposure without requiring a change in lens opening and without introducing a color shift. Neutral density filters are denoted by (Optical) Density value.
an extremely gradual blend is required, an "attenuator" is used. It changes density almost throughout its length. The key to getting best results with a Color-Grad filter is to help the effect blend in as naturally as possible. Keep it close to the lens, to maximize transition softness. Avoid having objects in the image that extend across the transition in a way that would highlight the existence of the filter.
dependent. A blue sky will not be equally affected in all directions. The areas of deepest blue are determined by the following "rule of thumb." When setting up an exterior shot, make a right angle between thumb and forefinger. Point your forefinger at the sun. The area of deepest blue will be the band outlined by your thumb as it rotates around the pointing axis of your forefinger, directing the thumb from horizon to horizon.
and black-and-white imaging. They have no recommended filter factors, but may require exposure compensation based on several things. Filters that lower contrast or create flare, where contrast and/or light intensity is higher, will do more for any given grade. Working with light, the more they have, the more they can do. The same filter, in two different lighting conditions, may produce two different effects.
attention to the presence of the filter, especially with stronger grades, when diffusion is not required elsewhere. It may be desirable to lightly diffuse adjacent scenes or subjects, not otherwise needing it, to ensure that the stronger filtration, where needed, is not made obvious. In diffusing faces, it is especially important that the eyes do not get overly soft and dull. This is the theory behind what might be called circular diffusion filters.
enhanced beauty. A first in this field is the fact that the filter is both effective to look at as well as to look through. The filter has a distinct silver sparkle that has been found to be doubly useful. When production starts and people see the glittering on the front of the lens, they become more confident in the knowledge that the filter is working for them and they may also turn in a better performance.
Smoque® filters create the look of smoke without the hassle. Mechanical generators are often used to add atmospheric haze to a scene. This could be for enhanced realism in places where smoke is normally encountered like a nightclub, or the scene of a fire. Most often, the smoke is added to create a certain “look”.
The number of directions that lines run in determines the number of points produced. Lines in one direction produce a two-pointed star, just a streak through the center of the light. There are 4, 6, 8, 12 and more points available. With an 8 or 12 point filter, the many star lines will tend to overpower the rest of the image, so use them carefully.
darken the blue, and lighten the orange; a blue filter will perform the reverse. A green filter, such as Wratten #11, can be used to lighten green foliage, to show more detail. It may also be used to provide more pleasing skin tones outdoors, especially against blue sky. Any filter used for the above purposes will have a greater effect if slightly underexposed. Its function depends on absorbing light of its complementary colors to increase the proportion of light of colors similar to itself.
filters for exposure control. Color Compensating Filters Color Compensating filters are used to make adjustments to the red, blue or green characteristics of light. These find applications in correcting for color balance, light source variations, different reversal film batches, and other color effects. They are available in density variations of Cyan, Magenta, Yellow, as well as Red, Blue, and Green filters.
Fluorescent and Other Discontinuous Spectra Lighting Correction Since filters never actually add color, but only absorb certain wavelengths to increase the relative proportion of others, the original light source must have the colors you want in it to start with. Some sources are totally deficient in certain wavelengths, which cannot be added back using only filters. This is particularly true of many types of metal halide lighting.
Similar to graduated ND filters (see earlier section for additional details), Color-Grad color filters are also produced in a wide range of standard and custom colors, densities, and proportions for many applications. A Blue-to-Clear filter can add blue to a white, hazy sky without affecting the foreground. An Orange-to-Clear filter can enliven a tepid sunset. Color can be added to the bottom of the scene, as with a Green-to-Clear filter used to enrich the appearance of a lawn.
correction to balance out any unwanted bias in these other areas, the effect on reddish objects will still be apparent. Underwater Color Correction Filters When imaging underwater, the light you are recording is filtered by the water it passes through. Longer wavelength reds and oranges are absorbed until only blue is left. The actual effect is determined by numerous factors, such as light source (sun or artificial), water quality, and the water path.
requires no exposure compensation, and makes sufficient adjustments to the film to enable the timer to match the color of a properly 85-filtered original. It is not an all-around replacement for the 85. Use it only where needed for exposure purposes, and for subsequently printer-timed work. SPECIAL APPLICATION FILTERS Contrast Viewing Filters Balancing lighting by eye is a matter of experience. Decisions can be aided through the use of contrast viewing filters.
Effect of Depth of Field and Focal Length Changes Standard color filters generally function without change through variations in depth of field and focal length. This may not be true of many of the "special effect" filter types. There are no solid rules for predicting the variation in filter effect due to depth-of-field or focal length changes. There are some things we can expect, however. Let's look at a fog/mist type filter that causes a light to glow, or flare.
further aligning the lights in the image with their secondary reflections where possible, can minimize this problem. In critical situations, it may be best to make use of a matte box with a tilting filter stage. Tilting filter(s) of good optical quality only a few degrees in such a unit can divert the secondary reflections out of the lens axis, out of the image, without introducing unwanted distortion or noticeable changes in the filter's effect.
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