(UV Photogalleries: Flowers, Nature and architecture or Canon EOS 350D or Infrared-, UV- and Full-spectrum photography: Sony DSC-W1 or Infrared-, UV- and Full-spectrum photography by Canon EOS500D converted to full-spectrum photography.

If you want to see the extraordinary world as insects can see by their UV-sensitive eyes, you must become engrossed in a new dimension of the view to the environment — to the Ultraviolet Photography.

Firstly we must explain some basic terms about spectral characteristics of the light. From the photographic view of point (derived from the properties of photographic materials), as visible light is characterized the radiation in the wavelength range between 400-700 nm. When the light (radiation) have a higher wavelength (above 700 nm) then this light is named infrared (from this is derived infrared photography). UV range starts when the wavelength is below 400 nm. The UV range falls into three subcategories: UV-A (320-400 nm), UV-B (280-320 nm) and UV-C (below 280 nm). Potential harmfulness of UV radiation increases rapidly when the wavelength decreases, so UV-B is much more hazardeous than UV-A.

When you photograph under UV light (UV photography, don't make mistake with UW photography, i.e. photography under water, see, for example, my photos in this gallery) you are interesting mainly in optical properties of lens and filter and films' sensitivity to the UV light.

The best light source for UV photography is a blazing sun or direct daylight but you may also to use special UV flash units (classical flash units can have "glass" before lamp made from some plast that absorb UV light!), xenon or mercury lamps. UV light has a very diffuse character and you can obtain soft shadows even under strong sunlight. UV photos have often slight contrast and sharpness. These characters are originated i) by the different light diffraction in air for wavelengths of light in UV region then for radiation in the visible region and ii) by the reason that ordinary lens are not optically corrected to the UV light. In this context one must keep in mind that if you want to despatch haze you will use filter for block of UV light and on the contrary when you will photograph under infrared light (IR photography) you will obtain clear picture without any haze. From these reasons in UV photography you will obtain soft, dreamlike photos (mainly in the photography of the landscape).

Lens

Modern optics pass only little radiation below 400 nm. In this view of point UV photographer has considerably worse pose than IR photographer (taking photos in the infrared region). He has two principal choice in the selection of lens:
1. If you have a lot of money or if you know that UV photography is amazing and you want make these photos regularly — you may buy quartz-fluoride lens by Nikon – UV-Nikkor 105 mm f/4.5. As I read, it is wonderful choice (see pages of Bjorn Rorslett
2. If you want try this access to the photography but you are tight in money (and you must support your children, wife, dog, mistress etc. ..) than you have to make another selection from these two possibilities: a) You can use fix-focal lens with the lower amount of optical elements and so lower thickness of the glass. You have to realize that anti-reflex coating also absorb UV radiation. From this point of view you can obtain old, uncoated camera lens (preferably pre-WW II) in the second hand. Another choice is the copying lens. These older lenses nearly certainly doesn't contain the optical polymers. You can also use (buy) single coated lens. In this term and in the our (Czech) conditions I mean mainly lenses with marks "Made in USSR". They have, with respect to the price, relatively quality optics. I bought Helios 58/2 and it costs 180 Kc (approx. 10 DEM). Of course, you can try modern-day multicoated lens but you must be cautious and you must try permeability of this lens to UV light. b) You may use your current (multicoated) "consumer" zoom lens. These lenses have higher amount of optical elements and so higher thickness of the glass and they often contain lens made from optical polymers. This solution isn't recommended but don't believe to the all what is printed or what you hear. When we compare permeability of lens to the UV light we have to take into consideration the construction of lens, i.e. amount of lenses/group. For example, Helios 58/2 has 6/4, Canon 28-80 has 10/10 and 75-300 has 13/9. The change between these lenses in the UV permeability is roughly 4 EV (i.e. 16 times!), see table hereinafter. It's possible to conclude that this solution is usable, but you must keep on mind that exposition will be hardly prolonged.

The last possibility, when we waste of difficulties with optical qualities of lens, is using pinhole cameras. Anybody who like experiments with ancient (nowadays yet again booming) procedures, it may be warmly encourage. Many references exist about these problems on the internet, many from them you will find over references at the foot of this article. My article about this topic (with photos) you can see here.

Digital camera

Generally it is possible (as anyone said) to use digital camera very well for UV photography - minutiae find at e.g. Bjorn Rorslett. In this area is probably the most interesting usable of digital manipulation of UV nad IR pictures.

Filter

Perhaps it's clear, that to the UV photography it's necessary to filter off visible radiation. To this purpose they are using special ("black"; UV-pass) filters (these are otherwise "genuine" UV filters, but name UV filter is established for filters filtering UV radiation!). To this purpose it is possible to use filter from several manufacturer: Kodak Wratten 18A (the most known), Hoya U-360 (this is probably not yet produced) and Schott UG-1. I bought filter B+W 403 (made from glass Schott UG-1; transmission curve). Its price was at June 2000 1250 Kc (cca 70 DEM) and it is necessary to order it.
Filtrr B+W 403: internet shop B&H PhotoVideo

Film

From the film point of view you have, as in the case of "normal" photography, 2 possibilities – black&white and colour material.

B&W photography — most panchromatic films are sensitive to the light in ultraviolet region. Details about spectral characteristics you can to obtain, for example, on this address: materials. Myself I examinated old "East" Gemany film Orwo NP15 and new Czech film Fomapan 100. Both films had roughly the same sensitivity to the UV light.

Colour photography — here you must fix common problem (reality), that producers still innovate their films and they are also adding UV filtering matters into the sensitive layers (so that consumers can easy photo on holiday at the seaside).

A) negative films — I don't recommend them. They can originate two difficulties: i) coloured layers mostly contain UV filter hence rise problem with sensitivity to UV radiation and ii) problem with faithful reproduction of colours in lab (who knows, how looks right coloured version of UV photos - automatic machine of lab certainly no, author in many cases also don't know it).

B) slide films — the best choice are, according to data in the literature, tungsten-balanced films (they have shift spectra colours toward blue). From them is the best Fuji RTP. The shift of spectral sensitivity is visible at spectral sensitivity curves for daylight film (Konica Chrome R-100) and tungsten-type film (Fujichrome 64T type II). In galleries you can compare photos on these films (Konica Chrome R-100 and Fujichrome RTP II). Tunsten-balanced film seemes to me more sensitive to the UV light (diference was about 3 EV!).

Resulting colours in UV photography not have to be strictly blue, but they can contain also e.g. red. It's a matter of fact, among others, on spectral sensitivity of film and UV-passing filter. It is possible to obtain interesting impression while using IR films, from those some indicate also sensitivity for UV radiation – for example Kodak High Speed IR. In this case you can to obtain UV nad IR image.

Focussing

This apparently simple activity is a complicated problem. Lenses are corrected for the visible radiation and frequently they have also drawing symbols for focussing in infra-red areas. But what can do UV photographer, the member of "underprivileged and terrorized" minority group? Hand down universal (and "logical") theorem sounds, that UV needs the opposite correction of IR. Matter of this isn't indeed simple - depends, whether have you achromat, apochromat, mirror lens, or even only simple lens (for details see here). To the test of right focussing of yours lens it is necessary to use many films and lose lashings of times. Besides change in focussing can depend on the focus distance.

A simple thing works good for me: I made right focus, hold up shutters mostly on f=11, put on UV-pass filter and exposed.
Depth of focus (DOF) was sufficient (and results were better than when I tried about resharpening how on closer, so also farther distance). This way originates also my macro-photography of flowers under using close-up lens (+2D).

Some practical tips

Exposition. It is necessary to try your own lenses. In the table I mention my discovered results for exact lenses obtained at summer (June and July) in Czech Republic. Another situation will be obtained on the north (e.g. Norway), in the other season (winter with snow?). TTL measurement of exposition isn't usable for this purpose (at least at my Canon EOS300), it is necessary to use experimentally finding correction factors and these factors applicate to the exposition data measured by TTL without UV-pass filter. When you use close-up lens (+2D, B+W) you must increase value of correction factor about 2-3 degree. But also in all cases it is necessary to make bracketting because it is impossible to evaluate value of UV light in the photographed scenery (it depends for example on the amount of clouds, time etc.). According to data of Rorslett about quartz lens UV-Nikkor, TTL with this lens works without correction with connection to Nikon F4; in the case of F3 and F5 you must applicate correction factor +1, resp. -1.

Table of suggested correction factors (EV) in UV photography (filter B+W 403)
valid for Czech Republic (50° north latitude), summer and winter
Canary Islands (29° north latitude), summer - correction factor is approx. about 1-2 EV lower

Lens	Helios 58/2	Canon EF 28-80/3.5-5.6	Canon EF 75-300/4-5.6 III USM
B&W negative (Fomapan 100, Orwo NP15, Kodak TMax 100)	5-6	9-10	9-10
Color film for slides - Fujichrome RTPII	7-8	11-12	11-12
Color film for slides - Konica Chrome R-100	10-12	14-16	14-16

In the case of photography of flowers we can see that blooms looking for us as monochromatic have another appearance at UV light. We can recognize another designs, shades, patterns that can be very pleasing for insects and therefore atract their attention. The most common situation is that center of bloom (with pollen and stigma) is darker but some more interesting patterns can occur (see Photogallery–Flowers).

The diffuse character of the ultraviolet light is visible on the photos of landscape and architecture (you can give soft shadows even under strong sunlight).

I think that resulting UV photos are not only interesting experiment but we can look at another dimension of the nature that is invisible for our eyes. This situation help us to realize that not all in nature is constructed for human and that many things are out of our perception even though they have their purpose and signification. UV photography is, alike infrared photography, usable in various domains of science but its application is relatively petty than infared photography. From some examples we can mention archeology or dermatology.

In conclusion I must make some correction. Insect have, in the reality, UV-sensitive eyes but they also see in the visible spectra. In essence the seeing is moved towards to the UV range (in the most cases insect is blind for red). Of course, insect has compound eye and human has ventricular eye and for this reason comparison of these two eyes fails. The processing of image is, in the case of ventricular eye, very complex proces proceeding in the brain and anywise comparison with insect collapse.

This was a brief introduction. Now you are welcome in my UV–Photogalleries!

Filtrr B+W 403: internet shop B&H PhotoVideo

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Links to another UV photography pages
Bjorn Rorslett
Hank Hogan
Fumio Yokozawa
Materials
Beyond Visible - Ultraviolet, Infrared and Luminescence Photography (Shane Elen)

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