Sunscreen on back under normal and UV light

Ultraviolet photography is a photographic process of recording

image An image or picture is a visual representation. An image can be Two-dimensional space, two-dimensional, such as a drawing, painting, or photograph, or Three-dimensional space, three-dimensional, such as a carving or sculpture. Images may be di ...

s by using

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes: * ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...

from the

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

(UV)

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

only. Images taken with ultraviolet radiation serve a number of scientific, medical or artistic purposes. Images may reveal deterioration of art works or structures not apparent under

light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

. Diagnostic medical images may be used to detect certain skin disorders or as evidence of injury. Some animals, particularly insects, use ultraviolet wavelengths for vision; ultraviolet photography can help investigate the markings of plants that attract insects, while invisible to the unaided human eye. Ultraviolet photography of archaeological sites may reveal artifacts or traffic patterns not otherwise visible. Ultraviolet images have no color since ultraviolet radiation is invisible to human eyes. Photographs of dyes that

fluoresce Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with color ...

under ultraviolet illumination are examples of ultraviolet fluorescence photography.

Overview

Light (visible electromagnetic spectrum) covers the spectral region from about 400 to 750

nanometer 330px, Different lengths as in respect to the Molecule">molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling Despite the va ...

s. This is the

spectrum used in normal

photography Photography is the visual arts, art, application, and practice of creating images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is empl ...

. The band of radiation that extends from about 10 nm to 400 nm is known as

ultraviolet radiation Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of t ...

. UV spectrographers divide this range into three bands: * ''near UV'' (380–200 nm wavelength; abbrev. NUV) * ''far UV'' (or ''vacuum UV'') (200–10 nm; abbrev. FUV or VUV) * ''extreme UV'' (1–31 nm; abbrev. EUV or XUV). Only near UV is of interest for UV photography, for several reasons. Ordinary air is opaque to wavelengths below about 200 nm, and most transparent lens glass is opaque below about 180 nm. UV photographers subdivide the near UV into: * ''Long wave UV'' that extends from 320 to 400 nm, also called UV-A, * ''Medium wave UV'' that extends from 280 to 320 nm, also called UV-B, * ''Short wave UV'' that extends from 200 to 280 nm, also called UV-C. (These terms should not be confused with the parts of the radio spectrum with similar names.) There are two ways to use UV radiation to take

photograph A photograph (also known as a photo, or more generically referred to as an ''image'' or ''picture'') is an image created by light falling on a photosensitivity, photosensitive surface, usually photographic film or an electronic image sensor. Th ...

s - reflected ultraviolet and ultraviolet induced

fluorescence Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with colore ...

photography. Reflected ultraviolet photography finds practical use in

medicine Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, ...

dermatology Dermatology is the branch of medicine dealing with the Human skin, skin.''Random House Webster's Unabridged Dictionary.'' Random House, Inc. 2001. Page 537. . It is a speciality with both medical and surgical aspects. A List of dermatologists, ...

botany Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

criminology Criminology (from Latin , 'accusation', and Ancient Greek , ''-logia'', from λόγος ''logos'', 'word, reason') is the interdisciplinary study of crime and deviant behaviour. Criminology is a multidisciplinary field in both the behaviou ...

and

theatrical Theatre or theater is a collaborative form of performing art that uses live performers, usually actors to present experiences of a real or imagined event before a live audience in a specific place, often a stage. The performers may communic ...

applications.

Sunlight Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible spectrum, visible light perceptible to the human eye as well as invisible infrare ...

is the most available free UV radiation source for use in reflected UV photography, but the quality and quantity of the radiation depends on

atmospheric An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere ...

conditions. A bright and dry day is much richer in UV radiation and is preferable to a cloudy or rainy day. Another suitable source is electronic flash which can be used efficiently in combination with an

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

reflector. Some flash units have a special UV absorbing glass over the

flash tube A flashtube (flashlamp) produces an electrostatic discharge with an extremely intense, Coherence (physics), incoherent, full-spectrum white light for a very short time. A flashtube is a glass tube with an electrode at each end and is filled with ...

, which must be removed before the exposure. It also helps to partly (90%) remove the gold coating of some flash tubes which otherwise suppresses UV. Most modern UV sources are based on a mercury arc sealed in a glass tube. By coating the tube internally with a suitable

phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or ...

, it becomes an effective long wave UV source. Recently, UV-

LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...

s have become commercially available. Grouping several UV-LEDs can produce a strong enough source for reflected UV photography although the emission waveband is typically somewhat narrower than sunlight or electronic flash. Special UV lamps known as "

black light A blacklight, also called a UV-A light, Wood's lamp, or ultraviolet light, is a lamp (fixture), lamp that emits long-wave (UV-A) ultraviolet light and very little visible light. One type of lamp has a violet light filter, filter material, eith ...

" fluorescence tubes or bulbs also can be used for long wave ultraviolet photography.

Equipment and techniques

Reflected UV photography

In reflected UV photography the subject is illuminated directly by UV emitting lamps (radiation sources) or by strong sunlight. A UV transmitting filter is placed on the lens, which allows

radiation to pass and which absorbs or blocks all

and

infrared radiation Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

. UV filters are made from special colored glass and may be coated or sandwiched with other filter glass to aid in blocking unwanted wavelengths. Examples of UV transmission filters are the Baader-U filter or the StraightEdgeU ultraviolet bandpass filter, both of which exclude most visible and infrared radiation. Older filters include the

Kodak The Eastman Kodak Company, referred to simply as Kodak (), is an American public company that produces various products related to its historic basis in film photography. The company is headquartered in Rochester, New York, and is incorporated i ...

Wratten 18A, B+W 403, Hoya U-340 and Kenko U-360 most of which need to be used in conjunction with an additional infrared blocking filter. Typically such IR blocking, UV transmissive filters are made from Schott BG-38, BG-39 and BG-40 glass. Filters for use with digital camera sensors must not have any "infrared leak" (transmission in the infrared spectrum); the sensor will pick up reflected infrared radiation as well as ultraviolet, which attenuate the contrast and may even completely obscure the details that would be resolved by ultraviolet radiation alone. Most types of glass will allow longwave UV to pass, but absorb all the other UV wavelengths, usually from about 350 nm and below. For UV photography it is necessary to use specially developed lenses having elements made from

fused quartz Fused quartz, fused silica or quartz glass is a glass consisting of almost pure silica (silicon dioxide, SiO2) in amorphous (non-crystalline) form. This differs from all other commercial glasses, such as soda-lime glass, lead glass, or borosi ...

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

and

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs scal ...

. Lenses based purely on quartz show a distinct focus shift between visible and UV light, whereas the fluorite/quartz lenses can be fully corrected between visible and ultraviolet light without focus shift. Examples of the latter type are the Nikon UV-Nikkor 105 mm f/4.5, the Coastal Optics 60 mm f/4.0, the Hasselblad (Zeiss) UV-Sonnar 105 mm, and the Asahi Pentax Ultra Achromatic Takumar 85 mm f/4.5. Suitable digital cameras for reflected UV photography have been reported to be the (unmodified) Nikon D70 or D40 DSLRs, but many others are suitable after having their internal UV and IR blocking filter removed. The Fujifilm

FinePix IS Pro The FinePix IS Pro is a digital single lens reflex camera introduced by Fujifilm in 2007. It is based on a FinePix S5 Pro, which is in turn based on the Nikon D200. It has a Nikon F lens mount and can use most lenses made for 35 mm Nikon SLR c ...

digital SLR camera is purpose-designed for ultraviolet (and infrared) photography, with a frequency response rated from 1000 to 380 nm, although it also responds to somewhat longer and shorter wavelengths. Silicon (from which DSLR sensors are made) can respond to wavelengths between 1100 and 190 nm.

UV induced fluorescence photography

Photography based on visible

induced by UV radiation uses the same ultraviolet illumination as in reflected UV photography. However, the glass barrier filter used on the lens must now block all ultraviolet and infrared radiation, permitting only ''visible'' radiation (light) to pass. Visible fluorescence is produced in a suitable subject when the shorter, higher energy ultraviolet wavelengths are absorbed, lose some energy and are emitted as longer, lower energy visible wavelengths. UV induced visible fluorescence photography must take place in a darkened room, preferably with a black background. The photographer should also wear dark-colored clothes for better results. (Many light-colored fabrics also fluoresce under UV.) Any camera or lens may be used because only visible wavelengths are being recorded. UV can also induce infrared fluorescence and UV fluorescence depending on the subject. For UV induced ''non-visible'' fluorescence photography, a camera must be modified in order to capture UV or IR images, and UV or IR capable lenses must be used. Filters are sometimes added to the UV illumination source to narrow the illuminant waveband. This filter is called an exciter filter, and it allows only the radiation to pass which is needed to induce a particular fluorescence. As before, a barrier filter must also be placed in front of the camera lens to exclude undesired wavelengths.

Forensic use

Ultraviolet photography was used as evidence in court at least as early as 1934. Photographs made with ultraviolet radiation can reveal bruises or scars not visible on the surface of the skin, in some cases long after visible healing has completed. These can serve as evidence of assault. Ultraviolet imaging can be used to detect alteration of documents.

Biology

Ultraviolet photography can reveal features of living things that are not visible to humans. For example, since it is known that animals such as pigeons, bees, and Jumping spiders, can see UV light, it is of interest to know what these animals are seeing in those wavelengths.

References

External links

UV digital photography

UV photography of plants, buildings, landscape

UV photography of jumping spiders with a converted DSLR

UltravioletPhotography.com
UV floral signatures & other UV photographs.