Spinning time into gold with slit-scan images


My blog of day before yesterday told of the process of recording things that move in front of a photo-finish camera (also called a slit-scan camera).

This is an S-Bahn train coming into the station. Its speed was constant, except at the end (right side) when it slowed down and stopped. The camera recorded it and compressed it into this curious image.

Here are two more examples of things moving in front of the camera at a relatively constant speed. People, moving in both directions in front of the camera are recorded all going left-to-right (notice in this image that some of their shadows go to the left, while most go to the right. This indicates that the person was walking from right to left). The window in the door of the ICE train is recorded by the camera in two places. That’s because the door either opened or closed while I was making the image (the door was directly opposite my camera). When the door remained closed it was recorded only as white pixels.

This image shows people moving in both directions in front of the camera. Those with shadows going to the left were walking right-to-left, while everyone else was walking left-to-right.

What happens when the camera moves and the subject stands still? While traveling by train in recent weeks I have had the opportunity to put my slit-scan camera (iPhone with slit-scan software) against the window and record the passing scene. When a train is whizzing along at a high rate of speed this does not produce much of anything interesting, but when the train slows down and travels at a more leisurely pace, the images possible from the window are sometimes painterly, sometimes abstract.

This is a scene taken from the train of passing scenery.

As with the photos in the last blog, anything that moves in front of the camera is recorded (faithfully or otherwise – it all has to do with speed in this case). Anything standing still is recorded as a series of stripes. Things close the the camera are recorded with greater speed than things at a distance. Trees are often recorded as a thin row of vertical dark pixels, while buildings in a middle distance are recorded close to normal.

In one scene, above, the train slowed to about 5 k/hr., and the resulting image looks almost normal. Converging tracks look almost like a still photo and there is only some distortion. Just minutes later, when the train was going 120 k/hr. the passing scenery becomes a mural of colored abstract lines:

This is an image that will go into the “avant-garde” section in my biography. It’s simply unintelligible, but it’s pretty!

When we returned from Salzburg I took a daring slit-scan image. I started the camera recording, and I carried the tripod upright as I walked through a crowd of people boarding a train. I just let it run. Sometimes I walked abruptly to the side to avoid a collision, other times I changed lanes to avoid people. Meanwhile the camera just kept recording.

If you click on this image, it will be enlarged. Click on “Full size is 5184 × 307” and it will enlarge a little more (I think you can click on it one more time). You can explore people and things in there that will show you just how odd the image is. Though it’s interesting, it’s not something I will be doing often.

In my next blog I’ll discuss the combination of digital slit-scan imaging and rotational panoramic imaging. When the two come together, you get true panoramic images, and they have the potential of being really nice.


About Brian Lawler

Brian Lawler is an Emeritus Professor of Graphic Communication at California Polytechnic State University, San Luis Obispo and was a Guest Professor at Hochschule München from September, 2021 to September, 2022. He writes about graphic arts processes and technologies for various industry publications, and on his blog, The Blognosticator.
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