Wratten number

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Wratten number

Wratten numbers are a labeling system for optical filters, usually for photographic use.

They are named for the man who founded the first company, Frederick Wratten

Frederick Wratten

Frederick Charles Luther Wratten was an English people inventor.Wratten started his career as a school teacher and organist, and moved to London in 1861 to become a clerk in the Photographic & Optical Warehouse owned by Joseph Solomon....
, a British inventor. Wratten and partner C. E. K. Mees sold their company to Eastman Kodak

Eastman Kodak

Eastman Kodak Company is a multinational corporation public company which produces imaging and photography materials and equipment. Long known for its wide range of photographic film products, Kodak is re-focusing on two major markets: digital photography and digital printing....
in 1912, and Kodak continued to produce "Wratten Filters" for decades. Even now, as of 2006, Wratten filters are still produced by Kodak, and sold under license through the Tiffen

Tiffen

Tiffen Manufacturing Corporation is a company in Hauppauge, New York, New York, U.S.A. which manufactures Filter for photography, and other professional film and photography-related products....
corporation.

Wratten filters are very much an active part of observational astronomy

Observational astronomy

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Encyclopedia

Wratten numbers are a labeling system for optical filters, usually for photographic use.

They are named for the man who founded the first company, Frederick Wratten

Frederick Wratten

Eastman Kodak

Tiffen

Observational astronomy

Observational astronomy is a division of the astronomy science that is concerned with getting data, in contrast with theoretical astrophysics which is mainly concerned with finding out the measurable implications of physical model s....
.

Filters made by various manufacturers may be identified by Wratten numbers but not precisely match the spectral definition for that number. This is especially true for filters used for aesthetic (as opposed to technical) reasons; for example, an 81B Warming Filter is a filter used to slightly "warm" the colors in a color photo, making the scene a bit less blue and more red. Many manufacturers make filters labeled as 81B which do similar but not exactly the same filtering of light, according to that manufacturer's idea of how exactly it is best to warm a scene, and depending on their manufacturing techniques. Some manufacturers use their own designations to avoid this confusion, for example Singh-Ray

Singh-Ray

Singh-Ray is an American maker of Filter .They are among the more expensive brands, and have a reputation for high quality and personalized service....
has a warming filter which they designate A-13, which is not a Wratten number. Filters used for printing press color separation or scientific photography tend to have less variation.

Reference Table

The commonly available numbers and some of their uses include:

Wratten number	Color	Filter factor Filter factor In photography, filter factor refers to the multiplicative amount of light a filter blocks....	F-Stops correction	Uses and characteristics
1A				Called a skylight filter, this absorbs ultraviolet radiation, which reduces haze in outdoor landscape photography Landscape photography Landscape photography is a genre intended to show different spaces within the world, sometimes vast and unending, but other times microscopic.... .
2A	pale yellow			Absorbs ultraviolet radiation.
2B	pale yellow			Absorbs ultraviolet radiation, slightly less than #2A.
2C				Absorbs ultraviolet radiation.
2E	pale yellow			Absorbs ultraviolet radiation, slightly more than #2A.
3	light yellow			Absorbs excessive sky blue, making sky look slightly darker in black and white images.
4	yellow
6	light yellow
8	yellow	2		Absorbs more blue than #3.
9	deep yellow			Absorbs more blue than #8.
11	yellowish-green			Color Correction.
12	deep yellow			Minus blue filter; complements #32 minus-green and #44A minus-red. Used with Ektachrome or Aerochrome Infrared films to obtain false-color results. Used in ophthalmology Ophthalmology Ophthalmology is the branch of medicine which deals with the Eye diseases and Eye surgery of the visual pathways, including the eye, brain, and areas surrounding the eye, such as the lacrimal system and eyelids.... and optometry Optometry Optometry is a health profession concerned with eyes and related structures, as well as Visual acuity, visual systems, and Visual perception in humans.... in conjunction with a slit-lamp and a cobalt blue light to improve contrast when assessing the health of the cornea Cornea The cornea is the transparency front part of the eye that covers the Iris , pupil, and anterior chamber. Together with the cilliary muscles, the cornea reflects light, and as a result helps the eye to dilate, accounting for approximately two-thirds of the eye's total optical power.... and the fit of contact lenses.
15	deep yellow			Darkens the sky in black and white outdoor photography.
16	yellow-orange			Like #15, but more so.
18A				Based on Wood's glass Wood's glass Wood's glass was developed by Robert Williams Wood as a light filter used in communications during World War I. His "invisible radiation" technique worked both in infrared daylight communication and ultraviolet night communications.... .
21	orange			Contrast filter for blue and blue-green absorption.
22	deep orange			Contrast filter, greater effect than #21.
23	light red
24	red			Used for color separation of Kodachrome tranparency film, complements #47B and #61.
25	red tricolor			Used for color separation and infrared photography Infrared photography In infrared photography, the film or used is sensitive to infrared light. The part of the visible spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging.... .
25A	red	8	+3	Strong contrast red filter used for color separation and infrared photography Infrared photography In infrared photography, the film or used is sensitive to infrared light. The part of the visible spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging.... in black and white film.
26	red
29	deep red			Used for color separation, complements #47 and #61. In black and white outdoor photography makes blue skies look very dark, almost black. In infrared photography, blocks much visible light, increasing the effect of the infrared frequencies on the picture.
32	magenta			Minus-green. Complements #12 minus-blue and #44A minus-red.
34A	violet			Used for minus-green and plus-blue separation.
38A	blue			Absorbs red, some UV and some green light.
44	light blue-green			minus-red filter with much UV absorption.
44A	light blue-green			minus-red, complements #12 is minus-blue and #32 minus-green.
47	blue tricolor			Used for color separation. Complements #29 and #61.
47A	light blue			By removing lots of light that is not blue, blue and purple objects show a broader range of colors. Used for medical applications that involve making dyes fluoresce.
47B	deep blue tricolor			Color separation.
50	deep blue
56	light green
58	green tricolor			Color separation. By removing light that isn't green, green objects like foliage show a broader range of colors.
61	deep green tricolor			Color separation, complements #29 and #47.
70	red			Used for color separation and infrared photography Infrared photography In infrared photography, the film or used is sensitive to infrared light. The part of the visible spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging.... .
80A	blue	4	2	Color Conversion. Raises the color temperature Color temperature Color temperature is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, and other fields.... , causing a 3200 K tungsten-lit scene to appear to be daylight lit, approximately 5500 K. This allows use of a daylight balanced film with tungsten lighting.
80B	blue	3	1+2/3	Similar to 80A; 3400 K to 5500 K.
80C	blue	2	1	Similar to 80A; 3800 K to 5500 K. Typically used so that old-style flashbulb Flashbulb The term flashbulb can refer to:Flash photographyThe Flashbulb, one of the pseudonyms of electronica musician Benn Jordan*A bonus track by Nirvana... s can be used on a daylight film.
80D	blue	1.5	1/3	Similar to 80A; 4200 K to 5500 K.
81A	pale orange	1.4	1/3	Warming filter to increase the color temperature slightly; this can also be used when shooting tungsten type B film (3200 K) with 3400 K photoflood lights. The opposite of 82A.
81B	pale orange	1.4	1/3	Warming filter, slightly stronger than 81A. The opposite of 82B.
81C	pale orange	1.5	1/3	Warming filter, slightly stronger than 81B, opposite of 82C.
81D	pale orange			Warming filter, slightly stronger than 81C.
81EF	pale orange		1/3	Warming filter, stronger than 81D.
82A	pale blue	1.3	1/3	Cooling filter to increase the color temperature slightly. The opposite of 81A.
82B	pale blue	1.4	2/3	Cooling filter, slightly stronger than 82A and opposite of 81B. Can also be used when shooting tungsten type B film (3200 K) with household 100W electric bulbs (2900 K).
82C	pale blue	1.5	2/3	Cooling filter, slightly stronger than 82B and opposite of 81C.
85	amber	1.5	2/3	Color conversion, the opposite of the 80A; this is a warming filter that takes an outdoor scene lit by sunlight (which has a color temperature around 5500 kelvin Kelvin The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero .... s) and makes it appear to be lit by tungsten incandescent bulbs around 3400 K. This allows an indoor balanced film to be used to photograph outdoors.
85B	amber	1.5	2/3	Similar to 85; converts 5500 K to 3200 K.
85C	amber	1.5		Similar to 85; converts 5500 K to 3800 K.
85N3	amber			Neutral Density of 1 stop + Color conversion, the opposite of the 80A; this is a warming filter that takes an outdoor scene lit by sunlight (which has a color temperature around 5500 kelvin Kelvin The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero .... ) and makes it appear to be lit by tungsten incandescent bulbs around 3400 K. This allows an indoor balanced film to be used to photograph outdoors.
85N6	amber			Neutral Density of 2 stops + Color conversion, the opposite of the 80A; this is a warming filter that takes an outdoor scene lit by sunlight (which has a color temperature around 5500 kelvin) and makes it appear to be lit by tungsten incandescent bulbs around 3400 K. This allows an indoor balanced film to be used to photograph outdoors.
85N9	amber			Neutral Density of 3 stops + Color conversion, the opposite of the 80A; this is a warming filter that takes an outdoor scene lit by sunlight (which has a color temperature around 5500 kelvin) and makes it appear to be lit by tungsten incandescent bulbs around 3400 K. This allows an indoor balanced film to be used to photograph outdoors.
87
87C	opaque			Passes infrared but not visible frequencies.
89B	near-opaque			Passes infrared, blocks visible wavelengths below 720 nm (very dark red). Aerial photography Aerial photography Aerial photography is the taking of photographs of the ground from an elevated position. The term usually refers to images in which the camera is not supported by a ground-based structure.... is one use.
90	dark grayish amber			Used for viewing scenes without color before photographing them.
92	red			color densitometry.
93	green			color densitometry.
94	blue			color densitometry.
96	grayish	varies		neutral density filter Neutral density filter File:Strickland Falls Shadows Lifted.jpgIn photography and optics, a neutral density filter or ND filter is a "grey" filter. An ideal neutral density filter reduces light of all wavelengths or colors equally.... . Blocks all frequencies of light evenly, making scene darker overall. Available in many different values, distinguished by optical density Optical density In optics, density is a unitless measure of the transmittance of an optical element for a given length at a given wavelength ?:\|\|\|= the per-unit opacity ... or by filter factor Filter factor In photography, filter factor refers to the multiplicative amount of light a filter blocks.... .
98	blue			Like a #47B plus a #2B filter.
99	green			Like a #61 plus a #16 filter.
102	yellow-green			Color Conversion; makes a barrier-level type photocell respond as a human eye would.
106	amber			Color Conversions; makes an S-4 type photocell respond as a human eye would.

Wratten number

Reference Table

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