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Infrared Imagery Part 2

27/01/13 - Written by Peter Jenkins

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Firstly, your digital camera will have to be specially modified by having had the internal IR filter removed. I had this done by Advanced Camera Services and it wasn't cheap - £450.00. Once the camera has been modified in this way, you cannot really use it again in its 'normal' mode.

I would only do this if you are after photographing very fine detail, otherwise the 'Nightshot' system on a video camera should suffice. The IR source can be from various illuminators such as an array of LED’s or by means of a conventional flashgun fitted with an IR filter. The modified flashgun is the preferred option as the illumination is more powerful which assists in capturing detail and better images at longer distances.

The Flashgun

The flashgun is screened with a piece of IR filter glass which is dark red in colour. The filter has to be fitted so that any stray white light does not escape from the flash in order to remain covert.

The Camera Settings

Firstly you should go through the cameras’ menu and the following adjustments:

Review: Switch off. This prevents the rear screen from automatically illuminating as it displays the image just taken

LCD Brightness: On low This keeps the rear viewing screen brightness down in the event you have to review the images

ISO: Set the cameras’ ISO to 400

Red Eye Reduction: Switch off. This prevents a beam of light firing out of some cameras

Manual Focus: This prevents the camera shooting out a beam of red light. In very poor light or total darkness, the camera lens is unable to focus unless it has something to focus on and so it emits this red beam. The disadvantage of manual focus, it that it can be tricky to focus on your subject in total darkness. If you are close up, set your cameras focus and use a tape measure or piece of string cut to length so that you know how close or far back to move the camera for the image to be in focus.

Auto Focus: As mentioned, when the camera’s lens is set to auto focus, a red beam of light is emitted from the camera. If the situation is secure and permits you to get away with it (such as being close up or indoors) then use it.

Program Mode

The cameras program mode should be set to Manual (M). You will now have to manually adjust the shutter speed and aperture to the desired settings. A bit of experimentation is now required by bracketing the shutter speed.

It is recommended that you always try to use the largest aperture possible (f2,8, f3.5 or f4.5) in order to let in as much light. However, if shooting very close up, it is recommended to set this to f8 in order to maximise depth of field (remember that IR light focuses at a different point)

So, with your cameras aperture set to f3.5, now set the shutter speed to 1/125th, wamr up the flash and take a picture.

Review the image: If it is too dark, then slow the shutter speed down to 1/90th, if it is to bright then use a faster shutter speed of 1/350th. Boldly experiment until you get it right.

Be aware of shooting at shutter speeds of less than 1/60th as you may encounter blurring through camera shake. To obtain a faster shutter speed, increase your ISO setting to 800 or 1600.

Once you have transferred the images to a computer, it may be worth considering changing the format from 'colour' to 'greyscale'. This will give you a black & white picture rather than one with a red tinge to it.

If you want to learn more, come and visit us on our two day photography course.

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