Advanced techniques in Digital Infrared Photography

Advanced techniques in Digital Infrared Photography

Once you have mastered recording Infrared Images on your camera, you will probably want to try and improve on image quality.
Using the Histogram on your camera will help greatly in getting the exposure right for your image.
But Histograms are another subject that can take hours of explaining.

above - is a nicely exposed histogram and this is what you should be aiming to produce.

above - shows the various levels of brightness within your histogram.

White Balance

One of the next things will be to remove that reddish tint that appears on your images, this can be done by pre-setting your white balance manually. Most DSLR cameras will have this function. To set the white balance you will need to point the camera at a Infrared white subject under the lighting conditions that you will be shooting under, your best subject here will be the green grass as this will come out as white under Infrared photography.
Of course you can also shot in RAW and set your white balance in your RAW editing software afterwards if you prefer.

above - Using Auto White Balance (left) and Using Manual Pre Set White Balance (right)

Focusing

Focusing is also different to visible light focusing, as the Infrared wavelengths are longer than visible light wavelengths.
So as the majority of Infrared photography will be landscape, then by using a small aperture should overcome any focusing errors.
But for more selected focusing then you either need to use a older type lens where they use to put a red or orange line to adjust for infrared photography. Or focus about 10% closer than you actually want in focus, but this does take a bit of practice.

above - Red Infrared lines on older type lens for infrared focusing

above - Both of these images were taken with the same camera, 70mm lens set to f2.8 and mounted on a tripod, approx 12in away from camera.

Right – Focused on 46in with visible light camera.
Left – Focused on 46in using visible light and manual focus then Infrared filter was fitted before taking photograph and as you can see the focus is now at 47in.

Different Infrared filters

Using different Infrared filters can give quite different effects.
Basically the lighter the filter (more towards the dark red end of the visible light scale 665nm). Then the more visible light is allowed through as well as the Infrared light giving a mix of colour and infrared wavelengths, this type of filter is more suited to colour photography as the monochrome will have less contrast.
The standard type of Infrared filter is something like the Hoya R72 which is rated at 720nm, this filter still allows some visible light through but also gives good monochrome results.
The darker filter rated at 830nm does not allow any visible light through so only deep monochrome results are possible with this filter.
Visit Digital Infrared Photography Sample Images. for more info

Infrared Flash Photography

To take Infrared Flash Images you need to put the filter onto a flashgun so that only Infrared light is emitted.
To do this you need to use some sort of filter and then block out any gaps between filter and flashgun so that no visible light can escape.

above - This is my homemade Infrared flashgun.

It has been covered in Clingfilm first, this is so that the tape that I used does not leave horribly sticky marks on my flashgun.
I then tape the Infrared filter directly onto the head of the flashgun so that no visible light can escape.
Then set your flashgun to manual full power (if adjustable), as we are only using the Infrared spectrum any other light will be wasted.
To take a picture using this technique will involve working in a darkened room.
Next you need to set up your visible light camera with no filters fitted onto a tripod as you will be using long exposures.
Again using manual controls with at least a 4 second exposure, set up your subject. Press the shutter release or use self timer and whilst the shutter is open fire off the flashgun at full power.
Remember about focusing when using this technique. As in the image below the camera was focused at front of plant using visible light, then the camera was set to manual focus (otherwise the camera lens will hunt trying to focus in a dark room) and manual exposure with a 4 second shutter speed (this will allow enough time to fire flash once shutter has opened) and aperture set at f2.8 to get as much Infrared light to record as possible. Next the room was darkened to take picture using self timer on camera.
This technique can be very much hit or miss, but you can have fun trying.

above - Picture taken using Visible light camera and a standard flashgun with a Infrared filter fitted. Note how in focus is at rear of plant even though camera focused at front of plant which was about 2 feet away from camera.

Monochrome Post Image Work

You will find that your Infrared Images will require quite a bit of work in Photoshop or other photo editing software to get the most out of them.
A quick way to improve these images is to open them in Photoshop CS2 or Elements. Then just use Auto Levels, Auto Contrast and Auto Colour, This should give you a reasonable image.
But there are much better ways of producing your final image depending upon which type of filter you used to take the image in the first place. If you used a lighter Infrared filter then you will be able to produce a colour Infrared image which requires a slightly different editing process to the more popular monochrome Infrared image.
First we will look at monochrome photography.
If you did not pre-set your white balance before shooting then your image will have a reddish tinge.
The next couple of images will show the process of editing a jpeg image straight from camera to final print using Photoshop CS2.

above - Open Image in Photoshop. You will notice the red tinge to the image.

above - Next we open the Channel Mixer and tick the monochrome box . Then we adjust the channel sliders to get the best results.

above - Next we open the Contrast controls and adjust as required

above - Now you may wish to sharper the image using the Unsharp Mask.

above - Finally we adjust the Levels.

above - Image straight out of camera.

above - Monochrome Image after being processed through Photoshop.

Colour Post Image Work

Now if you used a lighter Infrared filter that allowed some visible light in as well as the Infrared, then you will be able to produce a colour Image.
For colour Infrared it is best that you preset you white balance before taking picture unless you are using RAW, in which case you will need to import your RAW image into your Raw editor first and then set the white balance to about 2000K and colour tint to about -80.
The next set of slides will show you roughly how to produce a colour Infrared image using Photoshop CS2.

above - This image has come straight out of the camera where the white balance had been pre set.

The next couple of slides will show you how to return blue back into the sky, this process does not work with all sky images. I have set this process up as a 'action' in Photoshop.

above - We now open the Channel Mixer; you will note that the Red channel is at 100% while the others are at 0%

above - You will see that we have now set the Red Channel to 0% and the Blue Channel to 100%

above - We now open the Blue Channel which is at 100% while the others are at 0%

above - You will see that we have now set the Red Channel to 100% and the Blue Channel to 0%

above - Next we increase the Contrast

above - Then we adjust the Levels

above - Finally we use the Unsharp Mask

This is only the basic steps, it is possible to play around with Hue and Saturation in selected parts of the image.
Plus if you get any of the sky burnt out, it will become a yellow colour when the channels are swapped. But in fact it is a Cyan, so you need to return to the Channel Mixer and work with the Cyan channel highlighting the burnt out area using the colour picker, once you have selected this area decrease the saturation to -100% and increase the lightness to +100% this should blend in the burnt out sky.