Infrared photography is a very complex form of photography. During the lessons, you need to be very attentive to the process of setting up equipment and shooting. I have prepared a list for you, according to which it is convenient to check your actions. I advise you to print it out and put it in your bag along with the camera. All items on the list will be discussed later in the lesson.

Can your camera receive infrared rays?

Before you go out and buy a filter, test your camera for infrared sensitivity. Some cameras cannot do this. The easiest way to check this is to point the camera at the remote's LED light and press a few buttons on it. If you notice that the red light is flashing, then the camera is detecting infrared rays.

If the light from the LED is dim, then the camera detects infrared rays, but the exposure time will increase due to the internal filter blocking them.

If you don't see the LED blinking, set a long exposure and take a few shots while pressing the remote control buttons pointed at the camera lens. The photos should show the red light from the LED. If it is not there, then your camera cannot receive infrared rays, and this lesson will not help you.

Purchasing a filter

I have several suggestions when choosing an infrared filter. These are spin-on filters like Hoya, and square filters from Cokin.

Spin-on filters are a very good tool for infrared photography. One, they are relatively expensive. I advise buying filters from reputable brands for the best results. For example, I have a Hoya R72 filter, which impressed me very much with its results, even though it costs more than $100.

Square filters are quicker to put on or take off. At this point, the risk of spoiling the image with light rays is much higher than when working with winding filters. The average price for such a filter is $60.

If you're going to buy a large spin-on filter, get an adapter ring as well so that this filter will fit all other lenses. This saves you from having to buy a separate filter for each lens.

Wavelength and other options

The 720nm filter is considered the standard for infrared photography. I think it's worth starting with him. There are other options, for example, 900nm (RM90), but the prices for such filters are very high, they exceed $300. These filters are designed for professional infrared photographers with "big pockets".

There is another option in case you don't want to use a filter. You can set your DSLR camera to always detect the infrared spectrum. To do this, you need to calibrate the camera and lens. This is a very expensive service, after which your camera will only shoot in infrared mode.

When and where to shoot?

One of the most popular genres of infrared photography is landscape photography. Due to the effects created when shooting, the foliage can turn white when rendered, which will make the photo very gloomy and memorable. You can experiment with trees, flowers and grass.

Ideal shooting conditions are sunny days. In the rendering process (with incorrect color processing), the sky will be a deep blue color, and the leaves will be white. But this does not mean that in bad weather it is impossible to achieve the desired result.

If you set a long exposure time for the infrared filter, the results are almost the same as when working with Neutral Density (ND) filter. The photos will have a strong effect of movement.

Don't be afraid to experiment and don't limit yourself to simple situations and objects.

Lens Problems

Some lenses may produce anomalous infrared effects such as hot pixels. When this happens, you may notice a light, colorless spot in the center of the image. It happens that stripes appear throughout the photo. They can be removed in post-processing, but it takes a lot of time and effort.

Currently does not exist complete list lenses that work correctly, and those that create colorless spots. The site dpanswers.com provides a rather large list of most lenses and their problems.

1. Customization

Camera setup is very important to get good infrared photography. Do not install a filter until you have adjusted the focus, exposure, and white balance.

First, set up your camera on a tripod. Hang your camera bag on a tripod hook to maximize the entire tripod and minimize movement.

The following tips will help you get a clean image:

• Shooting in RAW format. Shooting in RAW will allow you to easily change the white balance in post-production. Never shoot in JPEG format, otherwise you will get noise and other defects that will be very noticeable.
• Turn off Long exposure noise reduction. Since a long exposure time is necessary for infrared photography, you need to turn this option off. There will be no noise during processing. It will also help you change the intensity of the noise in post-processing.
• Turn on Exposure delay mode / Mirror Lock-Up. If you turn on any of these modes, you will minimize vibration when you release the shutter.
• Remote shutter release or timer. Using the remote control is not necessary, but can reduce the amount of vibration since you are not touching the camera while shooting. Alternatively, you can set the timer to 2 seconds.

2. White Balance

White balance is very good with infrared. You can use the preset values ​​or Pre-White Balance to get a normal balance under current conditions. In any case, you will need to take time for this in the post-processing process.

There is nothing wrong with using presets. For example, the Incandescent setting is the most appropriate.

Go to the White Balance menu and select PRE. Then do the following:

• Click OK.
• Select Measure and press OK.
• Select Yes and overwrite the existing information.
• Make sure the main part of the subject is green in the viewfinder. You can point the camera at a patch of grass.
• Take a picture and wait for the camera to respond. “Data Acquired” or “Gd” should appear.
• If the camera shows "Unable to acquire" or "No Gd", then check the exposure.

The result should be a photo with a strong red-orange-magenta tint. We will fix it in post-processing.

3. Focus and stabilization

Focusing can take a long time if there are no infrared markings on the lens. It's best to use a small aperture, such as f/20, to get good depth of field and minimize focus issues.

If your lens has IR focus marks, adjust the focus according to the focal length. If there are no such marks, then it will not be easy to focus on the object. The best thing you can do is set a small aperture to get a large depth of field. Because of this, the pictures will have good sharpness, but this does not mean that you can use a large aperture for a small depth of field. Without calibrating the lens for continuous infrared shooting, it is impossible to achieve the desired focus with a large aperture.

Focus on the subject first with normal Auto Focus. Then switch to manual mode. If you have a camera with a rotating ring on the lens, then be careful not to move the ring.

Any stabilization system must be disabled. Using VR/IS/OS is not recommended because the camera is mounted on a tripod and because the lens will make unnecessary corrections that can cause blur.

4. Aperture

One of the important settings for IR photography is a small aperture. It gives greater depth of field and minimizes the focusing problems described above.

5.ISO

In most cases, it is best to use the lowest light sensitivity (ISO) to minimize the amount of noise. Take into account the length of the exposure. I would recommend using an ISO of no more than 800 for shooting between 10 seconds and a minute. For exposures longer than 1 minute, use ISO 400 or less.

Any values ​​that exceed these limits increase the risk of getting a large number of noise and hot pixels in post-processing.

If you use ISO from 100 to 200, then the waiting time for IR exposure will be halved. An 8 minute exposure at ISO 100 will be reduced to 4 minutes at ISO 200. The amount of noise will increase slightly, but it will help you when time is very short.

6. Shutter speed.

Finally, let's talk about shutter speed. First you need to determine the exposure time. Get your stopwatch ready.

IR filters require a slow shutter speed. As with ND filters, you can calculate the amount of delay to compensate using the Exposure Calculator.

For example, if the visible light exposure is 1/30, ISO 100, f/11, and the best IR result is 1 second, then you should have a 5-stop light blocking filter.

7. Take a picture!

Now you can screw the IR filter to the lens. After that, do not change the settings and do not twist the focus ring. Press the shutter button and wait for the result!

In the second part of the lesson, we will deal with the processing of IR images in Lightroom.

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Translated from the site photo.tutsplus.com, the author of the translation is indicated at the beginning of the lesson.

I don't know about you, but I've always wondered: what would the world look like if the RGB color channels in the human eye were sensitive to a different wavelength range? Rummaging through the barrels, I found infrared flashlights (850 and 940nm), a set of IR filters (680-1050nm), a black and white digital camera (no filters at all), 3 lenses (4mm, 6mm and 50mm) designed for photography in IR light. Well, let's try to see.

On the topic of IR photography with the removal of the IR filter on Habré, we have already written - this time we will have more opportunities. Also, photos with other wavelengths in RGB channels (most often with the capture of the IR region) can be seen in posts from Mars and about space in general.

These are flashlights with IR diodes: 2 left at 850nm, right - at 940nm. The eye sees a weak glow at 840nm, the right one sees only in complete darkness. For an IR camera, they are dazzling. The eye seems to retain microscopic sensitivity to near IR + LED radiation comes at a lower intensity and at shorter (=more visible) wavelengths. Naturally, with powerful IR LEDs, you need to be careful - with luck, you can quietly get a retinal burn (as well as from IR lasers) - the only thing that saves is that the eye cannot focus the radiation to a point.

Black-and-white 5 megapixel noname USB camera - based on Aptina Mt9p031 sensor. I shook the Chinese for a long time on the topic of black and white cameras - and one seller finally found what I needed. There are no filters in the camera at all - you can see from 350nm to ~1050nm.

Lenses: this one is 4mm, there are also 6 and 50mm lenses. At 4 and 6mm - designed to work in the IR range - without this, for the IR range, without refocusing, the pictures would be out of focus (an example will be below, with a conventional camera and 940nm IR radiation). It turned out that the C mount (and CS mount with a working length that differs by 5mm) - we got from 16mm movie cameras of the beginning of the century. Lenses are still actively produced - but already for video surveillance systems, including famous companies like Tamron (4mm lens just from them: 13FM04IR).

Filters: I again found a set of IR filters from 680 to 1050nm from the Chinese. However, the IR transmission test gave unexpected results - it does not look like bandpass filters (as I imagined it), but it seems like a different "density" of color - which changes the minimum wavelength of transmitted light. Filters after 850nm turned out to be very dense, and require long shutter speeds. IR-Cut filter - on the contrary, it only allows visible light to pass through, we will need it when shooting money.

Filters in visible light:

Filters in IR: red and green channels - in the light of a 940nm flashlight, blue - 850nm. IR-Cut filter - reflects IR radiation, so it has such a cheerful color.

Let's start shooting

Panorama at night: you can see the difference in color of different light sources: "energy efficient" - blue, visible only in the nearest IR. Incandescent lamps - white, shine in all range.

Bookshelf: Virtually all ordinary objects are virtually colorless in IR. Either black or white. Only some paints have a pronounced "blue" (short-wave IR - 760nm) tint. LCD screen of the game "Just you wait!" - in the IR range does not show anything (although it works on reflection).

A cell phone with an AMOLED screen: absolutely nothing can be seen on it in IR, as well as a blue indicator LED on the stand. In the background - nothing is visible on the LCD screen either. The blue paint on the metro ticket is IR transparent - and the antenna for the RFID chip inside the ticket is visible.

At 400 degrees, the soldering iron and hair dryer glow quite brightly:

Stars

Photo of the first star in the evening with a conventional camera:

IR camera without filter:

Another example of the first star against the background of the city:

Money

1000 rubles with filters 760, 850 and 1050nm: only some elements are printed with ink that absorbs IR radiation:

5000 rubles:

5000 rubles without filters, but with illumination of different wavelengths:
red = 940nm, green - 850nm, blue - 625nm (=red light):

However, the infrared tricks of money do not end there. The banknotes have anti-Stokes marks - when illuminated with 940nm IR light, they glow in the visible range. A photo with a conventional camera - as you can see, IR light passes through the built-in IR-Cut filter a little - but because the lens is not optimized for IR - the image is not in focus. Infrared light looks light purple because Bayer RGB filters are transparent to IR.

Now, if we add an IR-Cut filter, we will see only glowing anti-Stokes marks. An element above “5000” glows the brightest, it can be seen even in dim room lighting and backlighting with a 4W 940nm diode / flashlight. There is also a red phosphor in this element - it glows for several seconds after irradiation with white light (or IR->green from the anti-Stokes phosphor of the same label).

The element slightly to the right of “5000” is a phosphor that glows green for some time after irradiation with white light (it does not require IR radiation).

Summary

There is a wonderful kind of photography that opens up a different, "parallel" world, hidden from the human eye - infrared photography. Images obtained with infrared filters allow us to get into a fairy tale, which at the same time is an integral part of our everyday space.

Infrared photography began in the film era, when special films capable of recording infrared radiation appeared. But since digital SLR Cameras much more popular than film ones and it has become quite difficult to get a special film (besides, it should be noted that not every film DSLR will allow you to shoot on IR film due to the presence of an infrared sensor inside the camera that will illuminate the frames), in this photo tutorial we will only touch on aspects infrared photography with digital SLR cameras.

To begin with, in order to understand the process of obtaining an infrared image, it is necessary to understand the theory. The radiation that forms a color image perceived by the human eye has a wavelength ranging from 0.38 μm ( purple) down to 0.74 µm (red). Peak sensitivity of the eye falls, as you know, on green color having a wavelength of approximately 0.55 µm. The wavelength range with a wavelength of less than 0.38 microns is called ultraviolet, and more than 0.74 microns (and up to 2000 microns) is called infrared. Sources of infrared radiation are all heated bodies.

Reflected solar infrared radiation most often forms an image on a film or camera matrix. Since infrared photography has found the most common use in the landscape genre, it should be noted that grass, leaves and needles reflect IR radiation best of all, and therefore they turn out white in the pictures. All bodies that absorb infrared radiation appear dark in the images (water, earth, tree trunks and branches).

Now we can move on to the practical part.

Let's start with filters. To obtain an infrared image, it is necessary to use IR filters that cut off most or all of the visible radiation. In stores you can find, for example, B + W 092 (transmits radiation from 0.65 microns and longer), B + W 093 (0.83 microns and longer), Hoya RM-72 (0.74 microns and longer), Tiffen 87 (0.78 µm and longer), Cokin P007 (0.72 µm and longer). All filters except the last one are ordinary threaded filters that are screwed onto the lens. Filters from the French company Cokin must be used with a proprietary mount, which consists of a threaded ring for the lens and a filter holder. The peculiarity of such a system is that for lenses with different thread diameters, you only need to purchase the appropriate ring, while the filter and holder remain the same, which is much cheaper than purchasing the same threaded filters for each lens. In addition, up to three filters with different effects can be mounted in the standard holder.

Since we are only looking at IR photography with digital SLR cameras, it should be noted that different camera models have different ability to detect infrared radiation. Camera matrices themselves perceive IR radiation quite well, however, manufacturers install a filter (the so-called Hot Mirror Filter) in front of the matrix, which cuts off most of the infrared waves.

This is done to minimize the appearance of unwanted effects in the pictures (for example, moiré). How strongly the IR radiation is filtered determines whether the camera can be used for IR imaging. For example, Nikon camera D70 with Cokin P007 filter can be removed from hands, and for Canon EOS 350D and most other cameras will always need a tripod due to slow shutter speeds. Some photographers who are passionate about IR photography resort to modifying the camera by removing the infrared filter.

Now let's touch on the processing of images in Photoshop. The resulting frames, depending on the white balance setting, will have a red or purple tonality. To get a classic black and white infrared image, you will need to desaturate the image, for example, using a gradient map, after adjusting the levels and contrast. There are also several ways to get very effective color infrared photographs. For example, you can use the Channel Mixer tool by first setting the red channel to Red - 0%, Blue - 100%, for blue - Red - 100%, Blue - 0%, and then by slightly manipulating the percentage of one or another color in channels to choose such values ​​at which the picture will look most attractive.

In conclusion, we note the main advantages of infrared photography: the absence of haze in the pictures and the always well-detailed sky, the absence of debris, since it does not reflect IR rays, and, of course, the most important thing that was said at the very beginning is the ability to see unusual, a non-everyday world in which, in addition to the fabulous color, all moving objects disappear or turn into "ghosts".

We need a piece of non-exposed, but developed reversible (that is, “slide”) film. Shooting with a digital camera through this cut of the slide, we get infrared images. In this case, the film acts as an infrared light filter.

The fact that such a film is completely opaque and black in appearance should not alarm us. The unexposed developed emulsion itself delays the radiation of the spectral range to which the film is sensitive (that is, the entire visible range), passing everything else (that is, the ultraviolet and infrared ranges). But, despite such "democracy" of the emulsion in relation to the invisible range, the plastic substrate of the film is not able to pass ultraviolet. Therefore, the combination "emulsion / substrate" remains to transmit only infrared radiation.

Matrix digital camera, as we know, is able to fix it, despite the efforts of manufacturers in the opposite direction. Since the lens of a camera, especially a reflex camera, has a fairly large diameter, it is recommended to use 120 format film. The width of such a film is 6 cm, so you can cut a piece of the desired size from it, unlike narrow-format film. It is not at all necessary to buy such a film and immediately develop it: ready-made unnecessary trimmings can be begged from the operator in any prolab. As a holder of such a "light filter", you can use everything that is at hand, including the hand itself. If our homemade IR filter has a convex-concave shape, then it must be straightened by putting it in the middle of a heavy book for a couple of days.

It is better to use film Fujichrome Velvia 100F or Agfachrome RSX II 100 which gives no worse result.

The disadvantages of the described method include a reduced contrast compared to real infrared images taken through a filter, and the low mechanical strength of a self-made "filter".

How do IR cameras work?

Infrared radiation is one of the types of radiation that cannot be seen by human eyes. Its wavelength is longer than that of light in the visible spectrum. Infrared illumination allows the camera to "see" even in complete darkness. This is made possible by a lamp or diodes that emit infrared light of a certain wavelength. Three wavelengths of 715 nm, 850 nm and 940 nm are common to infrared illuminators. The human eye is able to see up to 780nm and therefore can see slightly to illuminators that use 715nm. For true stealth night vision, IR illuminators operating at 850nm and 940nm must be used.

The lamp light is filtered so that only the pre-defined wavelengths of 715 nm, 850 nm and 940 nm are emitted.

DIY infrared filter for creative lighting nikon

These numbers are the starting points for the frequency of the emitted waves - they are the absolute lower limit of the spectrum used by the camera. If a person gets close enough, they will be able to tell that the camera is infrared, although they won't be able to see the wavelengths being used.

The ability of a camera to capture images based on light levels is measured in lux. The lower the lux value, the better the camera can see in low light conditions. All IR cameras are set to 0 lux, which means they can see in pitch darkness. Color IR cameras switch to black and white for video surveillance at night to achieve maximum sensitivity. A photocell inside the chamber monitors daylight and determines when a switch is needed. A distinction must be made between IR cameras and Day/Night cameras. Day/night cameras can work effectively in low light conditions, but they are not equipped with LEDs, which makes them impossible to work in complete darkness, unlike cameras with IR illumination.

When using IR cameras for outdoor use, it is better to use ready-made sets of outdoor cameras with a casing or cameras with an IR illuminator. Combining an indoor IR camera with an outdoor housing may not work well because the IR light can be reflected off the glass of the housing. In addition, when buying an IR camera or illuminator, you should always look at the value of the beam range. By installing IR cameras in a room with a wider range than the size of the room, you can get blurry images. It should be noted that IR cameras cannot see through smoke. In order to achieve this, a thermal imaging camera must be used.

Translation of Hi-Tech Security. Source: http://www.surveillance-video.com/ea-ir.html

Homemade infrared light filter

I think what infrared photography is, not everyone knows, but in vain, it's quite interesting thing. You can make an infrared filter out of film, but this article will focus on how to make an infrared filter out of a CD. The CD itself should be dark red, such discs are sold in many stores. What we need first of all is to take a cover from any plastic bottle, in my case it is mineral water, and cut a hole of as large a diameter as possible. The plastic bottle cap worked well as a lens attachment.

Photo #1

Next, the cut hole must be cleaned of burrs and painted with black car paint from a spray can or any other - just to hold on.

To clean the disc from the top layer, you need to draw a line from the middle to the edge with a knife, and under the pressure of water the top layer will quickly be washed off. Then three or two squares of the same size should be cut out of the disk and glued. Our homemade filter is ready, it remains only to stick it on a pre-prepared cap from a plastic bottle. Done, put the filter on the soap dish and go to photograph.

Photo #2

We will take pictures in the photo shooting mode " M", since we need access to all the settings of the soap box. It is advisable to take a tripod, but since I photographed on sunny days in the summer, there was enough light, at ISO 200 I was able to photograph landscapes handheld, the aperture was open, which reduced the sharpness of the picture.

Photo #3

With additional processing in Adobe Photoshop you can get the most different results: Reduce noise, tone or color the photo to your heart's content.

Photo #4

The pictures show that the infrared filter from the CD is not sharp enough, moreover, it rather creates the effect of a monocle. If you look at the channels of the image, then the red is constantly overexposed, and if it is present, then its sharpness is extremely low, the blue channel is the most contrasting, the green is not so, but the image is seen quite well.

Photo #5

Photographs taken with this filter are reminiscent of infrared shots: green foliage brightens, blue skies and water darken.

Photo #6

And if your soapbox supports the RAW format, the image can be made much more attractive, try it, and I'm sure you will do just as well! About the phototv site.

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Free program for webcam SplitCam allows you to add colorful webcam effects to your videos that will add fun to you and your friends! In addition, SplitCam is a simple and convenient way to split a video stream from a webcam.

DIY infrared digital camera

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In addition to the well-known paints for painting, there are special types of paints. They are used to protect the barcode and block infrared rays. Knowledge about them will expand our horizons and may even come in handy.

• Paints for protection of a bar code (bar code). Designed to protect the original barcode from photocopying.
• IR-blocking - paints that block infrared rays. Designed for printing on transparent PVC films, for the production of transparent plastic cards. These paints block or reflect infrared light. Radiation sources: ATMs or other similar reading devices.

Paints for protection of a bar code (bar code)
These inks are designed to protect the original barcode from photocopying. If such black ink is used, the original barcode will always be invisible to human vision. You can also apply this blocking ink under the overlaminate and then print the original barcode on the card on top. After lamination, it is no longer possible to separate the top layer from the base without damaging the barcode. All these paints do not contain carbon.

Standard colors:

• S 3374- red ink blocking a barcode that can be read with optical readers.
• S 4500- black and blue ink that blocks the barcode, which can be read using infrared readers.
• S4501- black-brown ink that blocks the barcode, which can be read using infrared readers.

Seal: Suitable for all types of stencils, except Stenplex Amber and Solvent self-adhesive films. It is recommended to use monofilament nets 77 T-90 T. When using a net with 90T cells, the covering power of the paint is 35-35 sq.m / kg.

Fixing:
Drying takes from 30 minutes to 1 hour depending on conditions. You can use jet drying.

Lamination: These inks can be printed directly over a printed barcode or overlaminated film and then laminated in the usual way.

Usage: Manufacturing credit cards points and tickets where barcode protection from photocopying is required.

Barcode blocking inks for printing on polyester films can also be supplied

IR-blocking

These inks are transparent inks that block or reflect infrared light. Radiation sources: ATMs or other similar reading devices.

Standard colors are transparent yellow and green.

Do-it-yourself infrared filter from a CD to a soap dish

These paints have different reflectivity. They are designed for printing on transparent PVC films, for the production of transparent plastic cards. These inks can be used for printing both on base films and laminating films.

Standard colors:

• S 17699- green IR blocker with a maximum absorption of 860-900 nm
• S18203- yellow IR blocker with a maximum absorption of 980 nm
  Both of these colors match ISO standard when printing through a grid of 90T.
• S21143- highly concentrated IR blocker with a maximum absorption of 980 nm
  This ink is ISO compliant when printed on 120T mesh.

To obtain other color shades, these inks can be overprinted with other transparent inks.

Seal:
Suitable for any type of stencil except Stenplex Amber and Solvent adhesive films. It is recommended to use monofilament mesh No. 90T, while the covering power of the paint is 60 sq.m / kg.

Fixing:
Drying takes from 30 minutes to 1 hour depending on the drying conditions. You can use jet drying.

Lamination:
These inks can be used to print directly onto a base film or onto a laminate, then laminated in the usual manner.

Usage:
Production of transparent credit cards for information reading through infrared readers and for identification by automatic teller machines.

"Cool! Physics" - on Youtube

Infrared and ultraviolet radiation.
Electromagnetic wave scale

« Physics - Grade 11 "

Infrared radiation

Electromagnetic radiation with frequencies in the range from 3 10 11 to 3.75 10 14 Hz is called infrared radiation.
It is emitted by any heated body, even if it does not glow.
For example, radiators in an apartment emit infrared waves that cause noticeable heating of the surrounding bodies.
Therefore, infrared waves are often called thermal waves.

Infrared waves not perceived by the eye have wavelengths exceeding the wavelength of red light (wavelength λ = 780 nm - 1 mm).
The maximum radiation energy of an electric arc and an incandescent lamp falls on infrared rays.

Infrared radiation is used for drying paintwork, vegetables, fruits, etc.
Devices have been created in which the infrared image of an object, invisible to the eye, is converted into a visible one.
Binoculars and optical sights are made that allow you to see in the dark.

Ultraviolet radiation

Electromagnetic radiation with frequencies in the range from 8 10 14 to 3 10 16 Hz is called ultraviolet radiation(wavelength λ = 10-380 nm).

You can detect ultraviolet radiation using a screen coated with a luminescent substance.
The screen begins to glow in the part on which rays fall beyond the violet region of the spectrum.

Ultraviolet radiation is highly reactive.
Photo emulsion has increased sensitivity to ultraviolet radiation.
This can be verified by projecting the spectrum in a darkened room onto photographic paper.
After developing, the paper will blacken beyond the violet end of the spectrum more strongly than in the visible spectrum.

Ultraviolet rays do not cause visual images: they are invisible.
But their effect on the retina and skin is great and destructive.
The ultraviolet radiation from the sun is not sufficiently absorbed by the upper atmosphere.
That's why you can't stay high in the mountains long time without clothes and without dark glasses.
Glass glasses that are transparent to the visible spectrum protect the eyes from ultraviolet radiation, since glass absorbs strongly ultra-violet rays.

However, in small doses, ultraviolet rays have a healing effect.
Moderate exposure to the sun is beneficial, especially at a young age: ultraviolet rays contribute to the growth and strengthening of the body.
In addition to a direct effect on skin tissue (the formation of a protective pigment - sunburn, vitamin D 2), ultraviolet rays affect the central nervous system, stimulating a number of important vital functions in the body.

Ultraviolet rays also have a bactericidal effect.
They kill pathogenic bacteria and are used for this purpose in medicine.

So,
A heated body emits predominantly infrared radiation with wavelengths exceeding the wavelengths of visible radiation.

Do-it-yourself infrared filter No. 2

Ultraviolet radiation is shorter wavelength and has a high chemical activity.

Electromagnetic wave scale

The length of electromagnetic waves varies over a wide range. Regardless of the wavelength, all electromagnetic waves have the same properties. Significant differences are observed when interacting with matter: the absorption and reflection coefficients depend on the wavelength.

The length of electromagnetic waves is very different: from 10 3 m (radio waves) to 10 -10 m (X-rays).
Light is an insignificant part of the wide spectrum of electromagnetic waves.
In the study of this small part of the spectrum, other radiations with unusual properties were discovered.

The figure shows a scale of electromagnetic waves indicating the wavelengths and frequencies of various radiations:

It is customary to single out:
low frequency radiation
radio emission,
infrared rays,
visible light,
ultra-violet rays,
X-rays,
γ radiation.

There is no fundamental difference between the individual radiations.
All of them are electromagnetic waves generated by charged particles.

Electromagnetic waves are detected mainly by their action on charged particles.
In a vacuum, electromagnetic radiation of any wavelength travels at a speed of 300,000 km/s.
The boundaries between individual areas of the radiation scale are very arbitrary.

Radiations of different wavelengths differ from each other in the methods of their production (radiation from an antenna, thermal radiation, radiation during deceleration of fast electrons, etc.) and methods of registration.

All of the listed types of electromagnetic radiation are also generated by space objects and are successfully studied with the help of rockets, artificial earth satellites and spacecraft.
First of all, this applies to x-rays and y-radiations, which are strongly absorbed by the atmosphere.
As the wavelength decreases, quantitative differences in wavelengths lead to significant qualitative differences.

Radiations of different wavelengths differ greatly from each other in terms of their absorption by matter.
Short-wave radiation (X-rays and especially γ-rays) are weakly absorbed.
Substances that are opaque to optical wavelengths are transparent to these radiations.

The reflection coefficient of electromagnetic waves also depends on the wavelength.

Would you like to know how the world around us would look if the human eye perceived light rays not only of the so-called "visible spectrum", but also far beyond it?

One way to see the world in a way that the human eye can't see is through infrared photography.

IR filter on the lens, a necessary element for infrared photography

For a long time from a purely technical, applied area, infrared photography entered the world artistic photography. By shooting in the IR range, you can get incredibly beautiful, "space" landscapes.

In general, this type of shooting and post-processing is a subject for a separate large article or even a series of articles. But today our goal is just to get to know the basics.

So how do you get an infrared image? There are many options. Previously, a special photographic film was used for this. In specialized digital technology, special matrices are used.

But you can try to take an infrared photo with a simple digital camera.

Infrared photography equipment

By and large, the optics of any camera transmits rays in the IR range. But the problem is that the matrices of modern cameras are equipped with special Hot-mirror filters. And these filters often almost completely cut off the IR spectrum.

There is an easy way to check if your digital SLR is suitable for infrared photography. Take a regular remote control - from a TV, music center, etc. All of them work on the basis of IR rays.

Put your camera on a tripod and in complete darkness take as many shots at different shutter speeds and apertures. At the same time, keep the remote control pointed at the lens and hold down any button.

If a bright dot appears on the frames taken, then the filter of your camera passes IR rays to a sufficient degree and you can move on. If not, then there are several options. Look for another camera or try to act further "at random". It is curious that relatively inexpensive soap dishes are often equipped with a weak Hot Mirror, and not fancy DSLRs.

Experiment with shutter speed and aperture. You may need a very long exposure to achieve the goal, so that the IR rays break through the filter.

Some go to great lengths, tuning the innards of their DSLRs for IR. If you decide to go down this path, then for this purpose it is quite possible to buy a “donor” from among used DSLRs inexpensively. The essence of tuning is the mechanical removal of the Low Pass filter, on which the Hot Mirror filter is usually mechanically deposited.

On the Internet, especially in English, there are many communities where there are detailed instructions for disassembling and removing filters from different camera models.

Mechanical filter removal after camera disassembly

The second integral part is the purchase of a filter for the lens. The most popular and proven models are Hoya R72 and Cokin 007. But given the expensive cost of IR filters (from $ 80-100), it makes sense to first test your camera with this filter, and not buy blindly in an online store.

True, there are manuals for making an IF filter from improvised means. But this is a separate conversation.

Landscapes look most interesting in the infrared range. This is due to the fact that, in fact, we fix the ability of objects not to emit, but to absorb IR waves. For example, the sky absorbs them in large quantities and in the picture it will go black, the green of the trees, on the contrary, reflects the rays and in the picture they will look white, as if covered with frost on a frosty day.

Given that when using IR filters, the amount of light entering the matrix is ​​extremely small, you will have to shoot at slow shutter speeds and therefore you will need a tripod.

Hoya R72 is one of the most popular infrared filters.

In addition, it is worth putting the camera into manual focus mode, as autofocus can shamelessly lie because of the filter.
Then it is worth experimenting with different exposure settings, analyzing the result.

After we got the coveted frame, we should do post-processing. Since a rare shot taken in the infrared range will be a masterpiece without processing.

There are a lot of processing methods. Consider one, the simplest.

Infrared photo processing

There are a huge number of techniques for post-processing (processing) infrared images. Consider briefly one of the simplest.

At the exit from the camera, you will get something like this.

Infrared photo exiting the camera

If you shot in RAW, it makes sense to change the white balance to make the greens as close to pure white as possible.

Then, open the image in Photoshop and adjust the Levels. It is better to do this for each channel separately (Red, Green, Blue).

Approximate view of Levels for a raw image

Levels correction - move the slider sliders to the edges of the histogram

As a result, our image will become more contrast and acquire visual “depth”.

Photo after changing the white balance and adjusting the levels

The next step is color inversion.

To do this, open the Channel Mixer (Image - Adjustments - Channel Mixer.)

Select the red channel and for it Red is removed to 0, and Blue is raised to 100

adjusting the Red channel

Then we open the Blue channel and do the opposite for it. Red at 100% and Blue at 0%

Adjusting the blue channel

Then click Ok and enjoy the result. To achieve a better effect, you can still work with the color saturation tools - Adjustments - Hue / Saturation

Final IF snapshot

Examples of infrared photographs

Well, for inspiration, so that you have a desire to still try to shoot in this technique, there is a large gallery of infrared images.