التصويرالفوتوغرافي مع الأنوار غير المرئية « UV » & « IR » .. مجلة فن التصويراللبنانية

Photography with invisible lights
"UV" & "IR"

The naked eye cannot see ultraviolet rays, as well as infrared rays, but photography can benefit from them, with the help of special materials and equipment in this field.

Photography with invisible light is an expression often used to describe photography that takes place in infrared and ultraviolet rays, and although some may scoff at these meanings - as long as light is visible by definition - the expression remains not abnormal, because it is very possible to take pictures Typical photography in all-black conditions.
Photography like this is more than a hoax, and is of great value in surveillance and in many scientific applications. In many cases, special materials, equipment, and methods are required, but infrared imaging remains possible even with a regular camera.
What we see as light represents just a part of the electromagnetic spectrum. It is radiation with wavelengths between 400 and 700 nanometers. - Violet light and red light respectively - but at wavelengths shorter or longer than these values, the eye does not see anything. But the radiation still exists, and it takes place in exactly the same way as visible light.

Radiation with wavelengths shorter than 400 nanometers down to one nanometer is called ultraviolet radiation (UV). Radiation that goes beyond red in the light spectrum at 700 nanometers is infrared radiation (IR), and this extends up to wavelengths of up to 14000 nanometers, provided that Photography can not record
The parts are from the UV and IR sectors only.

It is possible - within limits - to focus ultraviolet and infrared rays with lenses, thus affecting a distinct film with appropriate sensitivity. The other main requirements for photography with invisible light are sources of ultraviolet and infrared radiation that are sufficient luster and perhaps filters to reduce the wavelengths used or lenses that will not absorb radiation.

- Materials :
Photographic materials are sensitive to ultraviolet rays by nature, and this means that they can be used without modifications down to approximately 320 nanometers. gelatin In the sensitive layer, it begins to absorb ultraviolet rays. At that time, special materials containing very little gelatin or with fluorescent coverage are used.
As for the infrared film, it has a special pigment sensitivity to extend its normal sensitivity limits from 700 to 900 nm approximately. There are special materials that can reach a maximum of approximately 1300 nanometers. We note here that the infrared film is significantly granulated and needs to be kept cold to maintain its sensitivity.

There is also a special film, Intravel Ektachrome, which has a layer to sense infrared rays, and by means of an unconventional arrangement of photo dyes in the other layers, it produces false color effects. It is a film that has uses in the work of aerial exploration.

Lenses and focus:
When the ultraviolet rays and infrared rays
Red light has wavelengths that are somewhat different from that of visible light, and they are refracted by conventional lenses to a slightly different extent, as long as the amount of light refraction depends on the lens. Achromatic, designed to bring all colors of visible light to nearly the same focus point. But since the wavelength of light is mostly ultraviolet and infrared rays outside the normal range, they have different points of focus to some extent.
Fortunately, most lenses have an infrared focus indicator - usually a red line - on their focus scale, towards the side of the distance that is shorter than the normal signal, and the location of the distance shifts
after optical focus.
There is a special lens called superachromat that is of interest to the infrared spectral sector. Likewise, it is 400 to 1000 nanometers, and it does not need to be refocused, even for the work of aerial cameras’ lenses, correcting for infrared radiation in turn. It is worth noting that mirrors scatter light as do optical refraction lenses, so the lens of the clear woman called the catoptric system does not need Focus correction when working with infrared or ultraviolet rays, but all photographic mirror lenses also use some elements of optical refraction, also called catadrioptric lenses, and therefore they still need some refocusing.

For working with ultraviolet rays, the infrared index mark may be possible to use - because of the way the lenses are designed - if it is not possible to use, then a focus correction for different distances should be achieved by trial and error.

Light sources
Infrared radiation Although solar radiation is an abundant source of ultraviolet radiation, the rate of each of these two in solar radiation is small compared to its visible light. The electronic flash contains a similar percentage of ultraviolet radiation, while mercury vapor and fluorescent lights emit ultraviolet radiation. Hot thermal glow lamps (incandescent lamps), such as light flux lamps and flash lamps, are weak sources, as long as most of their energy is given in the visible and infrared sectors. red.

Infrared sources include the sun
The electronic flash and all forms of thermal glow lamps were studio lights.
All of these can be used in varying proportions for infrared photography.

Then, when visible light is not desirable, filters that transmit only infrared or ultraviolet light should be used. UV filters are made of a special type of glass called Wood's Glass, which is opaque.
And since ordinary glass absorbs ultraviolet radiation below about 300 nanometers, the lenses that are also used, such as molten silica - one of the forms of quarts - and calcium fluoride or fluorite, transmit up to 200 and 185 nanometers, respectively. These lenses are very expensive, and an example is the Zeiss UV Sonnar lens, 100 nm f / 4.3, which can be used for photography.
Visible light as well.
We point out that infrared filters—those not to be confused with thermal filters that absorb infrared radiation—are easy to get from regular retail customers—Rattin 87 is optically opaque but transmits infrared, for example. Such a filter can be used attached to a light source for photographing in the dark without notifying the subject. In this case, there is no need for a filter on the camera. Unless there are light sources from the field of view that may drown out the infrared image and eliminate it otherwise, and the alternative is that this filter can be used installed on the camera during daylight, in order to restrict the infrared image.
Moreover, since filters of this type are not transparent, they do not allow the use of an SLR viewfinder. The alternative, then, is the Ratin 25, which passes some deep red and allows for reflective viewing.

Use of x-rays:
Ultraviolet photography has many different applications in medicine and forensic sciences, but the high price of special lenses that are obtained by special request. It is beyond the reach of most hobbyists.
Infrared photography, on the other hand, requires relatively inexpensive films and filters.
This is in addition to using it at night. To detect or photograph wildlife, we find infrared rays can be used, for example, to penetrate fog, which is optically opaque. The reason for this is that the wavelength of visible light is in the same order and scale as molecules and fine particles in the air, while infrared waves are longer. The method is the same as with a large-wheeled tractor that can traverse an open field with ease, while a car that runs on wheels of the same size as a furrow quickly gets stuck and loses its ability to keep going.

Also, many photographers use infrared film because of the change in colors it causes.
If the film is black and white, the plants appear white, and the sky and water are black.
And on the false color infrared film, the colors are all different as plants appear red for example⏹