Porter's Camera Store April 2007 Newsletter

Infrared photography has always been fascinating and now digital photography makes it easier. Before, using Kodak infrared film was expensive to both purchase and process – especially given the hit-or-miss nature of exposing the film. With a digital camera that has all changed.

There is some expense involved with shooting infrared (IR from this point forward). First, the process requires a pricey Hoya R72 infrared filter, most cost between $40 and $80. This filter is nearly opaque and blocks most visible light while allowing infrared to pass. Next, you’ll need an editing program like Photoshop. Though other software will likely work, Photoshop will be used in this discussion.

The single biggest challenge may be your camera. Digital cameras use CCD or CMOS imaging sensors to capture images. A sensor is unusually sensitive to IR light, and that would seem to make it ideal for our purposes. However, IR can cause a “ghost” fringe around objects in our everyday pictures so camera manufacturers install a glass filter inside the camera to block IR wavelengths. Some cameras have very effective IR blocking filters and others are less effective. The only way to know for sure if your camera can take an IR picture is to try it!

Taking the Picture
The middle part of the day is usually avoided for most conventional outdoor photography, but that is the best time to shoot infrared. Objects that reflect IR (such as foliage and grass) will show as white or mostly white in the finished photo. Clear sky and calm water don’t reflect IR and will be black or tones of dark gray. Keeping these tones in mind, select a subject to shoot. (By the way, most skin will photograph pure even white).

To shoot IR images a tripod is required and a remote release is a good idea too. Set the camera to manual exposure mode, use manual focus and set the ISO to 400. Leave your camera set to take color images, don’t select monochrome or black and white for this experiment.

Now the educated guesswork begins. 400 ISO was selected as a starting point, but your camera’s results may cause you to shift this to a more sensitive 800 or a less sensitive 200 depending on your results. Next, set the lens aperture to f11 and the shutter to 10 seconds. Not 1/10^th of a second, but 10 seconds! Because of the various IR blocking filters used by camera manufacturers, this exposure is only a starting point. After some experience, you’ll be able to establish a more accurate starting point for your camera.

Since infrared wavelengths don’t focus at the same plane as visible light, focusing for IR photography needs a little compensation. Old style manual focus lenses had a red index mark that showed where to focus for IR imaging; most lenses today don’t have that aid. You’ll need to focus by eye and then re-set the focus on the short side of the scale. As an example if you focus on a point that the lens scale says is 40 feet away, shift your focus toward 30 feet. Using a best guess approach coupled with a small aperture like f11 can help you get sharper images.

Take several pictures, bracketing the shutter speed and aperture up and down until the image review shows an image with the best exposure value. Be aware that the images will look very red! The goal is an image with good tonality from dark to light. Favor an exposure that may seem a little overexposed.

Make a note of your camera setting and then continue shooting. The note you make will give a good starting point for another day’s IR shooting. Just remember that each shoot will require some experimenting with the exposure until you get an image that works. Cloud cover, haze and airborne pollutants will make each day’s exposure settings unique.

On the Computer
Open one of the better IR files into Photoshop. Generally you will see a very red tinged image that seems to have lower than normal contrast. Following these steps yields a very good false-color IR image.

When you first open your digital infrared photo, it has a strong red tint.

First open Image / Adjust / Channel Mixer. On the top pull-down menu select the Red channel. You will see that the Red channel is at 100% and the other two are at 0%. Change Red to 0% and change Blue to 100%.

From the top pull down menu select the Blue channel. Do the opposite here and set Red to 100% and Blue to 0%. Click OK to return to the main image window. Your image should look fairly blue at this point.

Next, select Image / Adjust / Levels. Select the Red channel from the drop down menu and move the rightmost marker below the graph until it just touches the foot of the black graph shape. We will next choose the Green channel and do the exact same process.

The final gross adjustment to make is to open Image / Adjust / Curves. At the bottom of dialog box, on the right side is an eyedropper for grays or mid-tones; click to select it. Move the mid-tone eyedropper over your image and use it to select a middle gray part of your image. With this click your major color balancing is finished. Save a copy of the file at this point before you begin any minor adjustments to brightness, contrast and color tone.

After making the adjustments, foliage appears very light while water, sky and other surfaces that absorb infrared are dark.

Sharpening should be your last step. My favorite method is to convert the image file into a LAB format Image / Mode / LAB. Then select the Channels tab behind the Layers palate. In the box you will see four channels, we only want the “Lightness” channel to be highlighted. To this channel apply your favorite sharpening method, I like to use “Unsharp Mask”. Once the sharpness is dialed in the way you like it, select the RGB channel to see the full sharpness effect. Convert your file back to Image Mode / RGB and your image is ready to print.

Why use LAB mode to sharpen? The vast majority of image noise appears in the blue sky portion of a shot. If we simply choose a “Sharpen” filter or apply a technique to an entire image, we also sharpen noise and make it more pronounced. By selecting only the “Lightness” channel in LAB Mode to sharpen, only the black tones in our image are affected.

If you choose to make a Black and White image as your final output you should still follow all of these steps before converting the image to monochrome. These adjustments will allow you to pull out the best contrast and tonality from your image file before converting to Black and White.