Tutorial

Tutorial - Creating a view into the world of infrared

Download the tutorial images: ir_tutorial.zip (1,633kb) filter_outline.zip (1,638kb)

This tutorial will take you through the steps of creating an image that serves as a good illustration of a view into the world of infrared. You will need one infrared photograph and one full color photograph taken from the exact same place (again, a tripod is ideal), a photograph of a filter, frame, or similar object, and Adobe Photoshop. For the purposes of this tutorial, I will be using Adobe Photoshop 5.0. The filter or frame will be used to frame the infrared portion of the image in the final composite. If you don't want to deal with finding, photographing, and masking the frame, you can use the one that I used in the above image.

First, open the image of the filter, or frame in Photoshop. You'll need to cut out the entire filter or frame, not including the center portion. If you do not know how to do this, use the filter included with this tutorial, and read up on masking later -- it's a good skill to have in your arsenal of image manipulation tricks.

Now, open both the color and infrared images. You'll probably want to auto-level the infrared image in Photoshop (Shift-Ctrl-L), or manipulate both images to make them look perfect before proceeding to the next step.


	Fig 4. The original infrared and color images (above), and the masked filter (left).

Our goal is to merge all three images into our final product. First, click on the window with the color photo to make it active. We're going to copy its contents into a new Photoshop document. Hit Ctrl-A to select the entire image, and then Ctrl-C to copy it to the clipboard. Now, create a new Photoshop document (Ctrl-N), accept the defaults in the window by clicking "OK" (it will automatically size to the size of the image you're copying), and paste the image into the new windows (Ctrl-V). You will see a copy of the color image in your new window. If you don't see the layers control window, select the menu item Windows->Show Layers to make sure it is visible. Double click the "Layer 1" layer and rename it to something more descriptive, like "Color Image". Now, save the new document and continue. I'm going to refer to this new document as the composite image from now on.

Now we need to copy the entire contents of the infrared photo into the composite image's window as a new layer. Copy the contents of the infrared photo into the new window by following the same steps above. Click on the infrared image's window, hit Ctrl-A and then Ctrl-C. Click the composite image's window, and hit Ctrl-V to paste in the new layer. You'll see a new layer labeled "Layer 1" appear in the Layers tab in one of the control windows. Double-click on "Layer 1" to change the name to something more descriptive, such as ""Infrared Image".

Do the exact same thing with the filter image, and rename the layer to "Filter".


Fig 5. The layers palette and current image

Now we have a document with three layers: a color image, an infrared version of the same image, and a filter. In the composite image's window, you should only see the infrared image with a filter on top of it because the color layer is being blocked by the ones above it in the list of layers.

Our next goal is to size the filter to an appropriate size, and then apply a mask to the infrared layer to let the color image through everywhere except for the area inside the filter. Select the "Filter" layer so that it is hilighted in the layers window. Now, select Edit->Transform->Scale from your menu bar. Click on one of the corner rectangles, and drag the cursor around while holding the mouse button down. When you let go of the mouse button, the filter will resize itself to fit in the bounding box you just specified. Note that you can hold down the Shift key while resizing to force the filter to stay circular. You can also move the filter around by clicking anywhere inside the box and dragging the cursor while holding the mouse button down. Adjust the size and position of the filter until you are happy. When you are done, double click anywhere in the box to commit your changes.

The final step is to reveal the color image in the area around the filter by creating a layer mask to control how different areas within the layer are hidden and revealed. In particular, we want to hide all portions of the infrared image outside of the filter, and reveal the portions inside the filter. We could just erase the entire area around the filter, but creating a layer mask lets us hide the area without actually destroying the original image. Click on the "Infrared Image" layer to make it active. Select the lasso tool from the control panel, and trace a circle along the ring of the filter while depressing the mouse button. Try to keep the lines from the lasso tool completely within the black area of the filter ring. When you've completed the ring, release the mouse button. You should see a moving dotted line along the path you traced. Don't be too concerned about drawing an exact circle -- the filter itself will hide any irregularities in the line.

Fig 6. The
lasso tool

Now that we've selected the portion we want to keep, we just have to create the layer mask. Select Layer->Add Layer Mask->Reveal Selection in the menu. The color image should suddenly appear around the filter, leaving us with our final image. Save the image now -- you're done!

Closing Notes

Infrared imaging has opened my mind to another way of looking at the world. Whenever I see the visual interaction of foliage with man-made object, I often try to imagine how the scene would look in other color spectra. I look up at trees framed by a brilliant blue sky, and imagine brilliant white forms against a black background.

With the quality of the current crop of new digital cameras, exploring infrared photography is finally a possibility for those of us who don't want to deal with the hassles of traditional infrared photography. While it is by no means a replacement for photography in the realm of visible light, it certainly adds a unique, creative twist to digital imaging.

Questions?Feel free to contact me at eric@echeng.com, or visit my website on digital infrared photography at http://www.echeng.com/photo/infrared/