Digital InfraRed Photography

June Newsletter
Greetings from
Porter’s Camera Store!

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 1/10th
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.

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