Photographic filter

src: tiffen.com

In photography and videography, the filter is a camera accessory consisting of optical filters that can be inserted into an optical path. Filters may be square or rectangular and mounted in holder accessory, or, more commonly, glass or plastic disks in metal or plastic ring frames, which can be screwed to the front or cut into the camera lens.

Filter modifies the recorded image. Sometimes they are used to only make subtle changes to the image; next time the picture will not be possible without them. In monochrome photography, color filters affect the relative brightness of different colors; red lipstick can be given as something from almost white to almost black with different filters. Others change the color balance of the image, so that the photographs under the incandescent light show the color as perceived, not with a reddish tinge. There are filters that distort the image in the desired way, spreading sharp images, adding star effects, etc. Linear and circular polarization filters reduce the inclined reflection of non-metallic surfaces.

Many filters absorb some of the available light, requiring longer exposure. Because the filter is on the optical path, any imperfection - the surface is uneven or not parallel, the reflection (minimized by the optical layer), scratches, impurities - affects the image.

There is no universal standard naming system for filters. The Wratten number adopted in the early 20th century by Kodak, which later became the dominant force in film photography, was used by several manufacturers. Color correction filters are often identified by the CC50Y - CC form code for color correction, 50 for filter strength, Y for yellow.

Optical filters are used in various fields of science, including in particular astronomy; they are essentially the same as photographic filters, but in practice they often require far more accurate optical properties and precisely defined transmission curves than specialized filters for photographic usage. Photographic filters are sold in larger quantities at lower prices than many laboratory filters. Articles about optical filters have materials relevant to photographic filters.

In digital photography, the majority of filters used with film cameras have been reduced by digital filters applied both to the camera and during post processing. Exceptions include ultraviolet (UV) filters that are normally used to protect the front surface of the lens, neutral density filters (ND), polarizing filters and infrared (IR) filters. Neutral density filters allow effects that require wide apertures or long exposures to be applied to lighter scenes, while neutral density filters that pass are useful in situations where the dynamic range of the scene exceeds the sensor's capabilities. Not using an optical filter in front of the lens has the advantage of avoiding image quality reduction caused by the presence of extra optical elements in the path of light and may be necessary to avoid vignetting when using a wide-angle lens.

Video Photographic filter

Use of filters in photography

Filters in photography can be classified according to their use:

• Remove and ultraviolet
• Color correction
• Color conversion (or light balance)
• Color separation, also called color reduction
• Contrast enhancement
• Infrared
• Neutral density, including neutral density filters and sun filters that pass
• Polarizing
• Special effects of various types, including
  • The graduated color, called the color gradient
  • Screen separator and cross star
  • Diffusion and contrast reduction
  • Places
  • Close-up or macro diopters, and split diopters or separate focus

Delete and ultraviolet

Remove filters , also known as window glass filters or optical layers, is transparent and (ideally) does not filter incoming light. The only use of a clear filter is protecting the front of the lens.

UV filters are used to block invisible ultraviolet rays, most of which are photographic and film sensors at least slightly sensitive. UV is usually recorded as if it were a blue light, so this non-human UV sensitivity can produce undesirable undesirable bluish hues of the atmosphere or, even more unnaturally, subjects in the open are illuminated by ultraviolet rich skies..

Typically, glass or plastic from a camera lens is practically opaque for short wavelength UV, but transparent against long wavelength (near-visible) UV. UV filters pass through all or nearly all visible spectrum but block almost all ultraviolet radiation. (Most spectral filter manipulations are named for the radiation they pass, green and infrared filters pass the color they name, but UV filter block UV.) Can be left on the lens for almost all shooting: UV filters are often used primarily for lens protection in the same way as crystal clear filters. Strong UV filters, such as Haze-2A or UV17, cut out some visible light on the purple part of the spectrum, and have a pale yellow color; This powerful filter is more effective in cutting fog, and can reduce purple fringing in digital cameras. Strong UV filters are also sometimes used to heat color photos taken in shade with daylight type films.

While in certain cases, such as harsh environments, protective filters may be necessary, there are also drawbacks to this practice. Arguments for the use of protection filters include:

• If the lens is dropped, the filter may have a scratch or rupture instead of the front lens element.
• Filters can often be cleaned without damaging the lens or lining surface; filters scratched with cleaning are much cheaper to replace than lenses.
• If there is a blow of sand, the filter will protect the front of the lens from abrasion and scratches.
• Some lenses, like some Canon L series lenses, require the use of filters to complete weather sealing.

Arguments against its use include:

• Adding other elements can degrade image quality if the surface is less than perfect and parallel. Filters from reputable authors are highly unlikely to cause problems, but some "cheaper" products are optically lower.
• Two additional reflections on the air glass interface inevitably result in a loss of light - at least four percent on each interface, if the surface is not coated; they also increase the potential for lens flare problems.
• A low quality filter may cause problems with auto-focus.
• Filters may not be compatible with the use of lens hoods, as not all filters have threading required for screw-caps or will allow hood-clips to be attached. Adding lens hoods over one or more filters can make the hood hood away from the lens causing vignetting.

There is wide variation in spectral UV blocking by filters described as ultraviolet.

Color conversion

The appropriate color conversion filters are used to compensate for unbalanced lighting effects for the stock color temperature of this film (typically 3200 K for professional tungstens and 5500 K for daytime): for example, the 80A blue filter used with film for daylight proofing is considered orange/reddish cast photocopy of photoflood incandescent photography (for which the ordinary photography term is "tungsten lighting"), and significantly increase the strong cast produced by low-temperature household incandescent lamps, while 85B will correct the bluish blueprint from daylight photos on tungsten films. Color correction filters are identified by non-standard numbers that vary from manufacturer to manufacturer. The need for this filter has been greatly reduced by the widespread adoption of digital photography, as color balance can be corrected by camera settings when images are taken, or by later software manipulation.

The color conversion filter (LB filter) must be distinguished from the color correction filter (CC filter), which filters out certain colors of f.e. caused by Schwarzschild effects etc.

Reduced color

The Color Alignment filter works by absorbing certain light colors, leaving the remaining colors traversed. They can be used to show the main colors that make up an image. They may be most commonly used in the printing industry for color separation, and again, use has been reduced because digital solutions have become more advanced and abundant.

Increased contrast

Colored filters are commonly used in black and white photography to change different color effects in a scene, changing the contrast recorded in black and white from different colors. For example, yellow or more dramatic filters, orange or red, will increase the contrast between cloud and sky by darkening the blue sky. The dark green filter will also darken the sky, and also add green foliage, making it stand out in the sky. Blue filters mimic the effects of older orthochromatic films, or even older films are only sensitive to blue light, blue rendering as light and red and green as dark, showing a blue sky as cloudy without the contrast between the sky and clouds, dark blond hair, making blue eyes almost white and red lips almost black. The diffusion filter reduces the contrast besides the softening resolution.

Polarizer

Polarization filters, which are used for color photography and black and white, are colorless and do not affect the color balance, but filter light with a certain polarization direction. This reduces the tilted reflection of non-metallic surfaces, may darken the sky in color photography (in monochrome photographic color filters more effectively), and can saturate more images by eliminating unwanted reflections.

Linear polarization filters, though effective, may interfere with the measuring and automatic focusing mechanisms when mirrors or file separators are in the path of light, as in digital single lens reflex cameras; circular polarizers are also effective, and do not affect the measurement or auto focus.

Neutral density

Neutral density filters (ND filters) are uniform density filters that weaken light from all the same colors. It is used to allow longer exposure (to create blur) or larger aperture (for selective focusing) than is necessary for correct exposure under prevailing light conditions, without altering the tonal balance of the photograph.

The multilevel neutral density filter is a neutral density filter with different attenuation at different points, usually evident in one and a half shadows to a higher density on the other. This can be used, for example, to take a scene with the inner dark shadows and brightly lit areas, where otherwise the shadow will not have detail or the spotlight will burn.

Cross screen

Cross screen filters , also known as star filters , create a star pattern, where lines radiate out from bright objects. The star pattern is generated by a very fine diffraction lattice embedded in the filter, or sometimes by using a prism in the filter. The number of stars varies by filter construction, as does the number of points each star has.

Diffusion

The diffusion filter (also called softening filter ) softens the subject and results in dream fog ( see photon diffusion ). This is most often used for portraits. It also has the effect of reducing contrast, and filters are designed, labeled, sold, and used for that purpose as well. There are many ways to achieve this effect, so filters from different manufacturers differ significantly. The two main approaches are to use some form of grid or mesh in the filter, or use something that is transparent but not optically sharp.

Both effects can be achieved in the software, which in principle can provide a very precise level of control of the level of effect, but the "look" may feel different. If there are too many contrasts in a scene, the dynamic range of the digital image sensor or film can be exceeded, which can not be compensated by post processing, so that contrast reduction when shooting is possible.

Lens diopter close-up and split

Although this is not a technical filter but an accessory lens, they are sold by filter manufacturers as part of their product line, using the same holder and attachment system. The close-up lens is a single converging lens or two elements used for close-up and macro photography, and works in the same way as glasses used for reading. The insertion of a converging lens in front of the retrieval lens reduces the focal length of the combination.

The close-up lens is usually determined by its optical power, as opposed to the focal length in meters. Some close-up lenses can be used in combination; the optical power of the combination is the sum of the optical forces of the lens of the component; a set of 1, 2, and 4 lens diopters can be combined to provide a range from 1 to 7 in step one.

A split diopter is only half a semicircle of the close-up lens in the normal filter holder. It can be used to shoot close and far more background objects, with everything in sharp focus; with a non-split lens the depth of field will be much too shallow.

Maps Photographic filter

Materials and construction

Photo filters are generally made of glass, resin plastic similar to those used for eyewear (such as CR-39), polyester and polycarbonate; sometimes acetate is used. Historically, filters are often made of gelatin, and color gel. While some filters are still described as "gelatin" or gel filters, these filters are no longer made from gelatin but from one of the plastics mentioned above.

Sometimes the filter is dyed in mass, in other cases the filter is a thin sheet of material flanked between two pieces of clear glass or plastic.

Some types of filters use other materials in glass sandwiches; for example, polarizers often use a variety of special films, filter nets have nylon mesh, and so on.

The rings on the screw filter are often made of aluminum, although on the more expensive brass filters are used. The aluminum filter ring is much lighter, but it can "bind" to the screwed aluminum lens yarn to, requiring the use of a filter lock to release the filter from the lens. Aluminum also dents or changes shape more easily.

High-quality filters are layered, with layers of optical layers to reduce reflections. Uncoated filters can reflect up to 12% of light, single-coated filters can significantly reduce this, and multiple layered filters can allow up to 99.8% of light to pass (0.2% unwanted reflections); light loss is not important, but part of the light is reflected in the camera, producing a flare and reducing the image contrast.

src: upload.wikimedia.org

Filter size and buffer

Manufacturers of lenses and filters have been standardized on several sets of different sizes over the years.

Threaded round filter

The most common filter sizes for circular filters include 30.5 mm, 37 mm, 40.5 mm, 43 mm, 46 mm, 49 mm, 52 mm, 55 mm, 58 mm, 62 mm, 67 mm, 72 mm, 77 mm, 82 mm, 86 mm, 95 mm, 112 mm and 127 mm. Other filter sizes in this range may be difficult to find because the filter size may not be standard or may be rarely used on camera lenses. The specified diameter of the filter in millimeters indicates the diameter of the male thread on the filter housing. Threaded pitch is 0.5 mm, 0.75 mm or 1.0 mm, depending on the size of the ring. Some sizes (eg 30.5 mm) come in more than one tone.

The filter diameter for a particular lens is generally identified on the lens face by? symbol. For example, a lens mark might indicate: "? 55mm" or "55?" meaning it will receive a 55mm filter or lens hood.

Square filter

For square filters, 2 "ÃÆ'â €" 2 ", 3" ÃÆ'â € "3" and 4 "ÃÆ'â €" 4 "are historically very common and are still made by some manufacturers. 100 mm - 100 mm very close to 4 "ÃÆ'â €" 4 ", allows the use of many of the same holders, and is one of the more popular measures currently (2006) used; it's almost standard in the film industry. 75 mm x 75 mm is very close to 3 "ÃÆ'â €" 3 "and while less common today, much of it is popular in the 1990s.

Cokin producers in France make various filters and holders in three sizes that are collectively known as Cokin System . The size of "A" (amateur) is 67 mm, "P" (professional) is 84 mm in size, and "X Pro" has a width of 130 mm. Many other manufacturers make filters to fit the Cokin holders. Cokin also makes filter holders for 100 mm filters, which they call the size "Z". Most of the Cokin filters are made of optical resins such as CR-39. Some round filter elements can be attached to rectangular/rectangular filter holders, usually polarizers and gradient filters that both need to be rotated and are more expensive to make.

The previous cokin (1980s to mid-1990s) had competition from Hoya's Hoyarex system (75 mm x 75 mm filters mostly made of resin) and also various made by Ambico, but both have been withdrawn from the market. A range of "systems" (84 mm) is still made (in 2012) by Formatt Hitech. In general, rectangular (and sometimes rectangular) filters from one system can be used on other system holders if the size is correct, but each creates a different filter retaining system that can not be used simultaneously. Lee, Tiffen, Formatt Hitech and Singh Ray also create a square/rectangular filter in sizes 100 ÃÆ'â € "100 and Cokin" P ".

Gel filters are very common in square shape, rarely used in circular form. It is a flexible sheet of gelatine or flexible plastic that must be held in a rigid frame so as not to sag. Gel is made not only for use as a photo filter, but also in different colors for use in lighting applications, especially for theater lighting. Gel holders are available from all square "system" makers, but are also provided by many camera manufacturers, by gel filter manufacturers, and by expensive professional camera camera makers (especially manufacturers who target the film and television camera markets.

The square filter system often has the lens shades available to attach to the filter holder.

Filter rectangle

Graduat filters of given width (67 mm, 84 mm, 100 mm, etc.) are often made oblong, not square, to allow the position of gradation to be moved up or down in the image. This allows, for example, the red part of the sunset filter to be placed on the horizon. This is used with the "system" holder described above.

Bayonet round filter

Certain manufacturers, notably Rollei and Hasselblad, have created their own bayonet systems for filters. Each design has several sizes, such as Bay I through Bay VIII for Rollei, and Bay 50 through Bay 104 for Hasselblad.

Series filter

Beginning in the 1930s, filters were also made in a sizing system known as mount series. The filter itself is round pieces of glass (or sometimes other materials) without the yarn. Very early filters have no rim around the glass, but the more common production filters then have glass mounted on metal rims. To install filters on the camera, filters are placed between two rings; either mounted rings are screwed into the lens thread or slip on top of the lens barrel and the retaining ring screw into the mounting ring to hold the filter in place. Serial titles are commonly written as Roman numerals, I to IX, although there are some non-written sizes such as Series 4.5 and Series 5.5. Most of the Series filter sizes are now obsolete, production has ceased in the late 1970s. However, the Series 9 becomes the industry standard of film and filter Series 9 is still produced and sold today, especially for professional cinematographic films.

src: upload.wikimedia.org

See also

• Gel color
• List of photography equipment makers
• Optical filter

src: previews.123rf.com

References

src: us.123rf.com

External links

• Photography Filter
• UV test filters - Description of results and summary - Lenstip.com
• Polarizing filter test - Results and summary - Lenstip.com
• Camera Filter Analysis | Camera Filters.biz

Source of the article : Wikipedia