Infrared photography tutorials

1) Conversion to the FULL SPECTRUM

The internal IR-blocking filter is removed and replaced with an optical glass of the same thickness and refractive index. Best if coated with antireflective layer. The replacement glass is important, since the thickness of the filter influences the focal length. If a thick hot mirror filter is only removed, the autofocus may not be able to compensate for this focal length change and will fail to focus.

The camera mode depends on your choice of mount-on filters. Several types of infrared filters may be tested as well as UV-pass filters. The camera may also take normal colour photos with B+W 486 filter.

This conversion mode is particularly suitable for compact and bridge cameras with a live preview.

Best for a photographer who wants to do experiments. See below what can you do with this camera:

Infrared photography - one needs to block all light but IR. This is done with the infrared filter. The filter appears as black to the naked eye since it allows only invisible IR light to pass. The full spectrum camera may be fitted with several types if IR filters.

Ultraviolet photography (UV) - one needs to block all light but UV. This can be done best with the "Baader U" filter. The cheaper B+W 403 filter will also do, but it produces mixed UV/IR images.

Normal colour photography - best results achieved with the B+W 486 filter. The hot mirror filter may also be used.

2) Conversion to the IR-ONLY

The internal IR-blocking filter is replaced with an infrared filter (cut-off 750 nm). The same rule for its thickness applies if using the autofocus. This conversion mode is particularly used for DSLR cameras, where the preview is only optical. It can also be used in compact cameras, but the camera will be permanently fitted with one type of IR filter only, so it will become a single-purpose IR camera. There will be no room for experiments, nor normal colour photographs may be taken. However, this camera may be successfully used with mount-on filters of cut-off values higher than 750 nm.

THE CHOICE OF FILTERS & EXPOSURE

The graphs below show the combined graph of the CCD sensitivity and the filter bandwidth. The yellow area represents the effective amount of light hitting the sensor and thus determining the exposure settings. The smaller the area the longer the exposure time is required at a chosen ISO and an F number. IR filters with higher cut-off wavelengths will provide more "pure" infrared photo, but it comes at a cost of longer exposures, lower F numbers, or higher ISO.

The area obtained with the R72 filter is similar to that obtained with the original camera, so one can expect a similar behavior, namely the exposure settings and autofocus proper functioning.

The autofocus in most compact camera models uses the contrast measurement method. This method functions when there is enough light (above the noise level) hitting the CCD sensor at the time. This means that if it is too dark, then the autofocus will fail - in the converted camera as well as in the original camera.

THE WHITE BALANCE

The white balance (WB) is set by default to AUTO. The picture processor analyzes the image and does the auto correction for the light source used. So, the white area photographed under yellow incandescent lamp will be mathematically corrected from yellowish to white together with all other colours. When this AUTO setting is kept for our converted camera, the images have a strong red tint. What about post-processing? Yes, it is easy to change the WB when shooting into the RAW format, but not so easy for jpeg. The camera allows for a CUSTOM WB setting, so you are in control! For outdoor shooting it is the foliage that appears bright, so one can define the grassland to be the reference for the WB setting. Try to set the camera WB to custom, then you will be asked to point the camera to the reference surface (grass) and take a picture. Make sure that the grass or other reference surface fills the LCD completely and that it is sufficiently illuminated. Higher camera models allow for two or more WB preset values. Just note that the custom WB setting is not available in the AUTO shooting mode (A). Consult the camera user manual for details. The manual WB setting is quite unique and adds to the originality of your image. And who said that it always has to be the grass? The possibilities are endless. The WB of the RAW (unlike JPG) image can be changed later using a PC software.

Results above were obtained with Canon G9 and the R72 filter using the following WB settings:

A - AUTO
B - Custom WB set for the grass with the IR filter on the lens
C - Custom WB set for the grass with the filter off the lens
D - Custom WB set for a yellow daffodil flower with the filter off the lens

Where to find more information about infrared photography?

The internet is a great resource for finding answers, so I recommend the following sites:

http://www.infraredphoto.eu/Site/GentleIntro1.html - interesting tutorial article with good examples

http://www.dmoz.org/Arts/Photography/Techniques_and_Styles/Infrared/ - infrared resource

http://www.naturfotograf.com/UV_IR_rev00.html - very good tutorials, detailed descriptions, more pages

http://www.xdeltax.com/infrared/index.html - tutorials on post-processing, great images

http://www.beyondvisible.com/BV6i-links.html - more links

http://www.dpfwiw.com/ir.htm - good technical overview

http://www.flickr.com/photos/publicenergy/sets/72157600200234603/ - IR gallery by publicenergy using my S5600-IR

http://www.flickr.com/photos/jonspage/sets/72157604038600757/ - IR gallery by Jon using my S5700-IR

http://www.lifepixel.com/ - US, converting cameras, especially DSLR - great DYI tutorials and video

http://www.maxmax.com/ - US, converting all kinds of cameras, gadgets, filters, etc.

http://www.bhphotovideo.com/ - they sell all kinds of filters you can imagine



	WHAT IS INFRARED PHOTOGRAPHY? The human eye can see the electromagnetic radiation ranging from 380 to 750 nm as colours of visible light. The silicon sensor chip in digital cameras can see more, from about 300 (UV) to 1100 (IR) nm. So, the cameras contain a filter, that blocks everything that our eyes can not see and would thus interfere with the picture (see the image a below). This filter is called "hot mirror" or IR-blocking filter and it blocks the IR light (figure a). If you place the IR-pass filter on such a camera, there will be very little light coming through and the exposure time will have to be very long (figure b). If we want to make the digital camera sensitive to IR (or UV), this IR-blocking filter has to be removed. Such a CONVERTED camera will be sensitive to IR and UV-A as well as to visible light (figure c below), unless the visible and UV light is blocked by the infrared filter (figure d). So the resulting images would be as follows: WHY CONVERSION? Since the exposure is given by the area under the spectral curve and actual light intensity, just compare the graphs a, b, and d with the corresponding photos below. Long exposure means that it is impossible to obtain sharp landscape images due to the smudging by the faintest breeze. The world is in the motion. The conversion makes it possible to take infrared images hand-held and opens the same possibilities as in normal colour photography. TWO TYPES OF CAMERA CONVERSION 1) Conversion to the FULL SPECTRUM The internal IR-blocking filter is removed and replaced with an optical glass of the same thickness and refractive index. Best if coated with antireflective layer. The replacement glass is important, since the thickness of the filter influences the focal length. If a thick hot mirror filter is only removed, the autofocus may not be able to compensate for this focal length change and will fail to focus. The camera mode depends on your choice of mount-on filters. Several types of infrared filters may be tested as well as UV-pass filters. The camera may also take normal colour photos with B+W 486 filter. This conversion mode is particularly suitable for compact and bridge cameras with a live preview. Best for a photographer who wants to do experiments. See below what can you do with this camera: Infrared photography - one needs to block all light but IR. This is done with the infrared filter. The filter appears as black to the naked eye since it allows only invisible IR light to pass. The full spectrum camera may be fitted with several types if IR filters. Ultraviolet photography (UV) - one needs to block all light but UV. This can be done best with the "Baader U" filter. The cheaper B+W 403 filter will also do, but it produces mixed UV/IR images. Normal colour photography - best results achieved with the B+W 486 filter. The hot mirror filter may also be used. 2) Conversion to the IR-ONLY The internal IR-blocking filter is replaced with an infrared filter (cut-off 750 nm). The same rule for its thickness applies if using the autofocus. This conversion mode is particularly used for DSLR cameras, where the preview is only optical. It can also be used in compact cameras, but the camera will be permanently fitted with one type of IR filter only, so it will become a single-purpose IR camera. There will be no room for experiments, nor normal colour photographs may be taken. However, this camera may be successfully used with mount-on filters of cut-off values higher than 750 nm. THE CHOICE OF FILTERS & EXPOSURE The graphs below show the combined graph of the CCD sensitivity and the filter bandwidth. The yellow area represents the effective amount of light hitting the sensor and thus determining the exposure settings. The smaller the area the longer the exposure time is required at a chosen ISO and an F number. IR filters with higher cut-off wavelengths will provide more "pure" infrared photo, but it comes at a cost of longer exposures, lower F numbers, or higher ISO. The area obtained with the R72 filter is similar to that obtained with the original camera, so one can expect a similar behavior, namely the exposure settings and autofocus proper functioning. The autofocus in most compact camera models uses the contrast measurement method. This method functions when there is enough light (above the noise level) hitting the CCD sensor at the time. This means that if it is too dark, then the autofocus will fail - in the converted camera as well as in the original camera. THE WHITE BALANCE The white balance (WB) is set by default to AUTO. The picture processor analyzes the image and does the auto correction for the light source used. So, the white area photographed under yellow incandescent lamp will be mathematically corrected from yellowish to white together with all other colours. When this AUTO setting is kept for our converted camera, the images have a strong red tint. What about post-processing? Yes, it is easy to change the WB when shooting into the RAW format, but not so easy for jpeg. The camera allows for a CUSTOM WB setting, so you are in control! For outdoor shooting it is the foliage that appears bright, so one can define the grassland to be the reference for the WB setting. Try to set the camera WB to custom, then you will be asked to point the camera to the reference surface (grass) and take a picture. Make sure that the grass or other reference surface fills the LCD completely and that it is sufficiently illuminated. Higher camera models allow for two or more WB preset values. Just note that the custom WB setting is not available in the AUTO shooting mode (A). Consult the camera user manual for details. The manual WB setting is quite unique and adds to the originality of your image. And who said that it always has to be the grass? The possibilities are endless. The WB of the RAW (unlike JPG) image can be changed later using a PC software. Results above were obtained with Canon G9 and the R72 filter using the following WB settings: A - AUTO B - Custom WB set for the grass with the IR filter on the lens C - Custom WB set for the grass with the filter off the lens D - Custom WB set for a yellow daffodil flower with the filter off the lens Where to find more information about infrared photography? The internet is a great resource for finding answers, so I recommend the following sites: http://www.infraredphoto.eu/Site/GentleIntro1.html - interesting tutorial article with good examples http://www.dmoz.org/Arts/Photography/Techniques_and_Styles/Infrared/ - infrared resource http://www.naturfotograf.com/UV_IR_rev00.html - very good tutorials, detailed descriptions, more pages http://www.xdeltax.com/infrared/index.html - tutorials on post-processing, great images http://www.beyondvisible.com/BV6i-links.html - more links http://www.dpfwiw.com/ir.htm - good technical overview http://www.flickr.com/photos/publicenergy/sets/72157600200234603/ - IR gallery by publicenergy using my S5600-IR http://www.flickr.com/photos/jonspage/sets/72157604038600757/ - IR gallery by Jon using my S5700-IR http://www.lifepixel.com/ - US, converting cameras, especially DSLR - great DYI tutorials and video http://www.maxmax.com/ - US, converting all kinds of cameras, gadgets, filters, etc. http://www.bhphotovideo.com/ - they sell all kinds of filters you can imagine
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