In these days of digital photography and post-production, the need for photographic filters is greatly reduced (polarising filters cannot be emulated in PhotoShop through and I still find my Lee Filters 0.6 ND grad useful); however, as I was clearing out my office last weekend, I found a useful list of the various filter types (possibly supplied with an old Hoya or Cokin filter) and I thought it was still useful information although some of the descriptions were a bit odd (so I’ve modified them slightly based on some Internet research):
| Filter | Description |
|---|---|
| Skylight | Absorbs ultraviolet rays (and blue/green). Often used for lens protection. |
| 1B | Used to eliminate blue cast in distant scenes and in shade. |
| UV(0) | Absorbs only ultraviolet rays. Makes distant scenes sharp and clear. |
| 80A (blue) | Colour conversion filter. Allows daylight-balanced colour films to be used with 3200°K lamps (tungsten bulbs). |
| 80B (blue) | Colour conversion filter. Allows daylight-balanced colour films to be used with 3400°K lamps (professional studio lamps). |
| 80C (blue) | Colour conversion filter. Allows daylight-balanced colour films to be used with 3800°K lamps (clear flash bulbs). |
| 81A | Light balancing filter. Allows Type B (tungsten balanced) colour films to be used with 3400°K (studio) lamps. |
| 81B | Light balancing filter. Eliminates strong blue cast when buildings, trees, etc., are photographed in daylight. |
| 81C | Light balancing filter. Prevents blue cast in cloudy or rainy weather. |
| 82A | Light balancing filter. Allows Type A (studio-balanced) colour films to be used with 3200°K (tungsten) illumination. |
| 82B | Light balancing filter. Type B filters can be used with 2900°K illumination (home bulbs). |
| 82C | Light balancing filter. Reduces the reddish cast found when shooting in early morning or late afternoon. |
| 85 | Colour conversion filter for use of type A (studio-balanced) colour films in daylight. |
| 85B | Colour conversion filter for use of type B (tungsten-balanced) colour films in daylight. |
| 85C | Colour conversion filter. Used to convert 5500°K (daylight) lighting to 3800°K. |
| FL-D | Eliminates green cast when daylight-balanced films are used under fluorescent lights. |
| FL-W | Eliminates green cast when tungsten-balanced films are used under fluorescent lights. |
| ND | Used to lower intensity of light striking the film to enable larger -apertures for shallow depth of field, slower speeds and special effects. |
| K2 (yellow) | Absorbs part of the spectrum between ultraviolet and violet. Makes clouds stand out. Also used for natural rendition of colors in black and white tones. |
| G (orange) | Absorbs part of the spectrum between ultraviolet and bluegreen. Provides stronger contrast than K2. Especially effective for distant scenes. |
| 25A (red) | Absorbs the spectrum between ultraviolet and yellow. Provides the strongest contrast. Makes daylight scenes appear as though photographed at night. Also used in infrared photography. |
| XO (yellow-green) | Transmits green and absorbs part of the spectrum between ultraviolet and blue. Natural rendition of skin and lips of female models. Highly effective for outdoor portraits. |
| X1 (green) | Absorbs more red than XO. Effective for reducing the reddish cast of lights for indoor photography. Suitable for photographing green trees and colourfu! subjects. |
This table just lists the technical filters but special effect filters are also available from the major filter manufacturers. For more technical information, check out Ken Rockwell’s post on how to use camera filters.