Color correction

Color correction

Color correction by using color gels, or filters, is a process used in stage lighting, photography, television, cinematography and other disciplines, the intention of which is to alter the overall color of the light; typically the light color is measured on a scale known as color temperature, as well as along a greenmagenta axis orthogonal to the color temperature axis.

Without color correction gels, a scene may have a mix of various colors. Applying color correction gels in front of light sources can alter the color of the various light sources to match. Mixed lighting can produce an undesirable aesthetic when displayed on a television or in a theatre.

Conversely, gels may also be used to make a scene appear more natural by simulating the mix of color temperatures that occur naturally. This application is useful especially where motivated lighting (lending the impression that it is diegetic) is the goal. Color gels may also be used to tint lights for artistic effect.

Contents

Correlated color temperature

Chromaticity diagram, Planckian locus, and lines of constant CCT.

The particular color of a white light source can be simplified into a correlated color temperature (CCT). The higher the CCT, the bluer the light appears. Sunlight at 5600K for example appears much bluer than tungsten light at 3200K. Unlike a chromaticity diagram, the Kelvin scale reduces the light source's color into one dimension. Thus, light sources of the same CCT may appear green or magenta in comparison with one another [1]. Fluorescent lights for example are typically very green in comparison with other types of lighting. However, some fluorescents are designed to have a high faithfulness to an ideal light, as measured by its color rendering index (CRI). This dimension, along lines of constant CCT, is sometimes measured in terms of green–magenta balance;[1] this dimension is sometimes referred to as "tint" or "CC".

Gel nomenclature

The main color correction gels are CTB (color temperature blue) and CTO (color temperature orange). A CTB gel converts tungsten light of 3200K to 'daylight' color. A CTO gel performs the reverse.[2] Note that different manufacturers' gels yield slightly different colors. As well, there is no precise definition of the color of daylight since it varies depending on the location (latitude, dust, pollution) and the time of day.

Gels that remove the green cast of fluorescent lights are called minus green. Gels that add a green cast are called plus green.[2] Fractions such as 3/4, 1/2, 1/4, and 1/8 indicate the strength of a gel. A 1/2 CTO gel is half the strength of a (full) CTO gel.

White balancing cameras

Color filters may be applied over a camera lens to adjust its white balance. In video systems, white balance can be achieved by digital or electronic manipulation of the signal and hence color correction filters are not entirely necessary. However, some digital cinema cameras can record an image without any digital filtering applied. Using physical color correction filters to white balance (instead of digital or electronic manipulation) can maximize the dynamic range of the captured image [2].

Some professional cameras designed for ENG use filter wheels containing color correction filters and are designed to optimize performance for different color temperatures.

In film cameras, no electronic or digital manipulation of white balance is possible in the original camera negative. Color correction filters are an effective method of adjusting white balance. Without filtering, one must attempt to fix white balance through color timing or by manipulating the film after it has been scanned or telecined.

References

  1. ^ "TLS,Inc. Technical Library - Filter Facts". http://www.tlsinc.com/toolfilterfax.html. 
  2. ^ a b John Jackman (2004). Lighting for Digital Video and Television (second edition ed.). Focal Press. ISBN 1578202515. http://books.google.com/books?id=21mbJwLyjz4C&pg=PA67&dq=%22color+conversion+and+correction+gels%22+intitle:lighting+inauthor:jackman+temperatures&lr=&as_brr=0&ei=WZ95SIqFAYP8swOjqJTPCQ&sig=ACfU3U2BIld6BzGFAT2FHHuybZUwx6JITw. 

Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • color correction —    The process of altering colors as they appear in a digital image or in print to insure they accurately represent the work depicted …   Glossary of Art Terms

  • Color Correction Filter — Farbfilter Als Farbfilter werden etwa Vorsatzfilter für Kameras bezeichnet, die nur eine bestimmte Farbe (Strahlung bestimmter Wellenlänge) passieren lassen oder die eine bestimmte Farbe herausfiltern (viel seltener). Sie werden meistens aus… …   Deutsch Wikipedia

  • Color grading — or colour painting, is the process of altering and enhancing the color of a motion picture, video image, or still image either electronically, photo chemically or digitally. The photo chemical process is also referred to as color timing and is… …   Wikipedia

  • Color suite — also called a Color bay or a Telecine suite or Color correction bay. Color suite is the control room for color grading video in a post production environment. The video source could be from: a telecine, a Video tape recorder (VTR), a motion… …   Wikipedia

  • Color balance — This article is about the process applied to still images. For the equivalent process applied to video, see Color grading. The left half shows the photo as it came from the digital camera. The right half shows the photo adjusted to make a gray… …   Wikipedia

  • Color gel — See also: Photographic filter Many color gels organized, some in gel frames A color gel or color filter (UK spelling: colour gel or colour filter), also known as lighting gel or simply gel, is a transparent colored material that is used in… …   Wikipedia

  • Color filter array — The Bayer color filter mosaic. Each two by two submosaic contains 2 green, 1 blue and 1 red filter, each covering one pixel sensor. In photography, a color filter array (CFA), or color filter mosaic (CFM), is a mosaic of tiny color filters placed …   Wikipedia

  • Color grading — PP The process of altering or enhancing the color of an image to seamlessly blend cuts together in a scene, remove unintended mistakes (e.g. overexposure of highlights) or for creative effect. Also known as color correction or color timing for… …   Audio and video glossary

  • Correction Gamma — En photographie, cinématographie et vidéo, le gamma caractérise le rendu en contraste d un support photosensible (émulsion photographique ou pellicule, capteur CCD ou CMOS...) ou d un signal visuel électronique. Du fait de la non linéarité des… …   Wikipédia en Français

  • Color photography — Color film redirects here. For the motion picture equivalent, see Color motion picture film. A circa 1850 Hillotype photograph of a colored engraving. Long believed to be a complete fraud, recent testing found that Levi Hill s process did… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”