You need a pair of 3D GLASSES with a RED and BLUE filter:

You can also use red and green glasses, but then you will see the pictures as monochromatic. Where to get the glasses? The glasses are not sold separately, to my knowledge, but you can often find them enclosed with magazines with 3D pictures. You can also buy transparent red and blue foil from a book store. The simplest way is just to cut out pieces (about 5x5 cm) of them, then place the red filter in front of your left eye and the blue one in front of your right eye. Then you can glue the filters on a suitably cut piece of cardboard or firm paper (see the image above).


You may notice that the colours are not totally realistic. This is because it is simply impossible to make full colour images using the anaglyph technique (for example, bright blue and red colours don't work). Besides, you can only see colour with the right eye (through the blue filter). The image seen through the red filter is always monochromatic.


The process of making 3D anaglyph photos consists of three main steps:

1. Shooting the double photos (one for each eye)
2. Scanning them into the computer
3. Combining them together as a red and blue (actually cyan) image

When the left eye image is cyan, it can only be seen through the red filter (in front of the left eye). The red right eye image can only be seen through the blue filter.

In case of 2D->3D conversions the steps are:

1. Scanning the 2D image
2. Processing the stereo pair from it using special techniques
3. Combining the two images as in the case of anaglyph photos

The left and right eye images can also be rendered from a 3D modelling software. Some of these produce anaglyph images directly.

The photos are taken with an ordinary camera. I take two photos of each target moving the camera horizontally to the right before taking the second picture, trying to keep the vertical focus unchanged. The distance to move the camera varies from some 10 cm to 50 cm depending on how far the target is; to get stereoscopic depth in objects located hundreds of meters away the "eye distance" must be strongly exaggerated. Taking both images with a single camera brings the restriction that everything in the picture must be immobile. Unfortunately I don't have a stereo camera yet.

The photos are then developed and scanned into the computer with a flatbed scanner. Then the digital pictures are processed in Adobe Photoshop in the following steps:

1. The pictures are rotated and positioned so that they match each other vertically as well as possible (partially after step 3).
2. Some general adjustments to brightness, contrast, colour saturation and other features are performed.
3. The left eye image is positioned over the right eye image as a separate layer (a feature in Photoshop).
4. The RED values of the right eye image are lifted to maximum with colour curves function. As a result the image becomes very red.
5. The left eye image is converted to black and white. The brightness curves must be adjusted in order to make the contrast match better the red image.
6. The BLUE and GREEN values of this images are lifted to maximum, which makes the image become totally cyan in colour.
7. The layer with the left eye image is applied over the right eye image with "multiply" function; this mixes the two images in the correct way.
8. The two images are further processed to match the brightness and contrast.
9. The images are flattened together to make a single anaglyph image.
10. Once more the image's brightness and contrast are adjusted, as well as sharpness.
11. In some cases there are colour "leaks" (some parts of the left image leak to the right eye or vice versa). It might be necessary to process the colour or darkness of such parts in detail.

It depends on the colours and contrast of the original photos how much effort it takes to make the 3D picture look good. For example, if there are bright red and blue colours, these must be altered before combining the images. Since the colours can only be seen with the right eye (through the blue filter), each of the images must be processed separately.

More about stereo photography at my stereoscopy pages.