Time Slicing

And  now for something completely different…

Claudio, Stella e Farfalla. Cetona, Italy. Jay Mark Johnson

I recently came across these rather amazing pictures by Jay Mark Johnson. He has taken a high resolution scanning panoramic camera (worth $85000!) and converted it into a static fixed viewpoint strip camera. This is not a new idea (all photo-finish cameras used in sport work in this way), but these photographs are really quite lovely and intriguing to look at.

Nicola Spirig wins the Women's Triathlon at the London 2012 Olympics (AP Photo/Omega)

We rarely stop to think that we are living in a four dimensional world – three spatial axes plus a fourth of time. When we take a single photograph, we flatten one spatial axis (depth) and squash time to a point, giving us a 2-D static image. In these time slice images only the vertical spatial dimension is captured (depth and horizontal information is discarded). But unusually, the dimension of time is recorded and transformed into the horizontal axis. You still have a static 2-D image of course, but you have to read the horizontal axis as time. With joiners where the camera is moved around between cells, you are capturing discrete points in time with different combinations of spatial information, so you end up with a ‘lumpy’ mixture of different spatial and temporal (time based) information.

Priscilla Electric Lodge #47-0. Jay Mark Johnson

A strip camera works by having a very narrow receptor for light. In this case, and for modern photo-finish cameras, this is a single line of photo sensors.  In the past, it was a narrow slit projecting onto film. Subsequent strips are recorded in very short periods, controlled electronically for digital devices or by precise advancement of the film for analogue cameras.

Los Osos. Jay Mark Johnson

Strip cameras have some interesting consequences. First off, things that move fast appear thinner than they would if they were slower. Static objects (ie the background) will record as plain strips.Generally, time runs from left to right, but this is only the way the camera is set up (in the 2012 Olympic photo finish picture time runs from right to left) . You cannot tell which direction someone was heading (left or right), only if they were going forward or reverse. In the picture of the man with the horse we know that they were moving forward (if time is running left to right). Things moving forward face left, things moving reverse face right. In these pictures, people moving forward face the past, whereas in normal space time if we move forward we look towards our future. How weird is that? Have a good look at the picture below (click on it to make it larger). You have got thick and thin people, moving slower and faster. Everyone is facing to the left,. The image was made in Italy, where cars drive forward on the right hand side of the road. So in fact, the two blue cars were actually travelling in space from left to right. Also, look at the shadows from the nearest people; some have shadows in front of them, some behind them. Which means they were travelling in different directions. If I've read this correctly then those with their shadows behind them must have been travelling left to right past the camera. Please let me know if you think I've got it wrong...

Il Mercato a Sinistra 1. Jay Mark Johnson

Strip photography effects are often seen on video devices that use a rolling shutter, giving characteristic ‘wobbly buildings’ when the camera is moved. In fact, just about every camera with interchangeable lenses is a form of strip photography camera. On all focal plane shutters the fastest speed at which the whole sensor or film is exposed all at the same time is the X-sync (typically 1/125 to 1/250), and is a function of the speed of movement of the shutter blades. Any speed above the X-sync speed will be achieved by creating a progressively narrower slit. My old Nikon FM2 had a very fast maximum shutter speed of 1/4000, which meant the film was exposed by a very narrow 1.5mm gap between the top and bottom shutter blades. It is however, very rarely that we see strip like distortions with modern high speed equipment. On very old cameras with large negatives a focal plane shutter took a fair time to pass over the film or plate, and could give some very strange effects, including my all-time favourite motoring picture taken by Jacques-Henri Lartigue.

Grand Prix de l'A.C.F. Automobile Delage. Jacques-Henri Lartigue 1912

Lartigue took this picture back in 1912 when he was just 17. I wonder how many of our children’s smartphone pictures will survive the test of time as well as this picture has?