jktales

Tales of Experimental Photography

The Story Behind LPP

"Second One" 2011

“Second One”, 2011. The second LPP picture I ever recorded

By Jiri Kudrna, May 2014

In July 2011 I was reading about scanning light photography and had one of these rare bright moments: What would happen if one would use line lasers instead of focused projector light? What if the light plane would be big enough to fit a whole person?

Two cheap red line lasers were lying around from a slit scanning project I was working on the year before. The whole installation was done in less than an hour. I had no exact idea what to do with it nor what the results might look like, so I just switched on the camera, pressed the shutter and moved my body through the light. I had immediately good results and was blown away.

Many experimenting sessions followed and my creative friends and I had a lot of fun exploring a completely new photography world. There were many evenings when we would stick, throw, turn and smear random materials and all sorts of odd objects through the light just to see what happens.

"Body On Glass", 2011. An experiment with a glass plate and background light

“Body On Glass”, 2011. An experiment with LPP and a window glass

During this time I coined the term “Laser Wall” and “Laser Wall Photography” which originates in the impression you have when standing in front of a light plane in a completely dark room. You can sense the presence of the light as the plane slightly illuminates any dust crossing it, it’s like there’s a wall of light in front of you. That term stuck until I decided to give it the more general name “Light Plane Photography” which describes the technique much better.

Although the results with the red lasers were good, they lacked resolution and the laser modules had only 60 degrees fan angle which was visible in most pictures. Also the optics used in these laser modules were very cheap. A few months later I decided to improve the installation and bought four green laser modules with cylindrical glass lenses and 120 degrees fan angle.

"Trophies", 2012

“Trophies”, 2012. From one of the first experimental sessions using 4 green line laser modules

During the same time period I built my first basic “Laser Wall Room”. This is a small room which is placed inside the dark studio. This room-in-room consist of two halves which do not touch each other but are separated by a narrow slit. The 4 laser modules are mounted in the corners of the room, outside, and pointed towards the slit which separates the two halves. All 4 laser lines need to be aligned to form the light plane. With this room-in-room installation there’s very little stray light in the inner room as the light plane does not touch the inside, this reduces unwanted ghost images of the model. One half of this first room was 2.5m x 2.5m x 1.2m. The back half was enclosed and there was an improvised curtain extending the front half in order to make place for the camera which had to be placed outside the room. This first “dark room” was constructed with lumber, plywood, rope and black cloth. It took me approximately two days to build it.

"Too Many", 2012

“Too Many”, 2012. A LPP image recorded using a green and two red light planes

I also started experimenting with more colors. At first I added two red lasers which were installed inside the dark room. These two lasers usually were not aligned but would add two separate planes either in front and/or behind the green plane. A few months later I also added two blue lasers which were problematic because they were barely visible in the pictures, they did not have enough output power compared to the green plane. In general, green is best visible because cameras are built after our eyes and they are most sensitive to green light. As a rule of thumb, in order to mix colors evenly you need twice as much laser output power for red and blue than you need for green.

"Detached Beautiful", 2012. A monochromatic LPP image with a sepia look which was added in post-processing

“Detached Beautiful”, 2012. A monochromatic LPP image in sepia look

The new green light plane with 4 lasers inside the dark room were a huge gain in overall picture quality. There is so much more details with green light. It also enabled us to experiment with much longer and shorter exposure times. Longer because we had less stray light inside the dark room and shorter because the green laser plane was much brighter than the two red lasers we used before. For the first time we were able to jump through the light plane or we could create complex choreographies which would take 20 or 30 seconds to finish.

 

In 2013 I designed a new dark room. This time it had to be completely enclosed and I wanted it to be modular so it could be easily setup at different locations. I decided for a steel frame construction covered in thin plywood, all painted black. The room was finished in November 2013 and named “The Reactor” for its crude, industrial look. The Reactor is about 3m wide, 2.6m high and 4.5m deep. It was another big step forward for overall picture quality. There’s very little if no ambient light and almost no stray light from the lasers. After all, at this point I was operating the plane with 800mW of laser power, which was 80 times more than the first tries with red lasers 2 years earlier.

The Reactor, a LPP dark room installation. The first image is one half, the second is the full installation with four laser modules, one in each corner

The Reactor, a LPP dark room installation. The first image is one half, the second is the full installation with four laser modules, one in each corner

Also during 2013 I started to contemplate how I could create real-color pictures: I needed a white light plane. I dismissed the solution with projectors as used in scanning light photography, it seemed very difficult to build a plane of this size using traditional optics. RGB laser modules used in laser projectors seemed to be a solution, they just had become available at prices I could afford. During a trip to Europe I built five RGB line lasers using relatively cheap 200mW modules from a Chinese seller on eBay and a central processor unit to control them. The central processor unit was necessary as I wanted to be able to have full control of color and brightness during photo sessions.

"Desta", 2013

“Desta”, 2013. Multicolor LPP image from an interactive session with the audience during an exhibition

These RGB modules proved to be much trickier than I had thought. There was huge differences in the output power of all the laser diodes and I could not fine tune them in order to get the same color from all modules. I also had problems with the line generating lenses I used and with the calibration of the 3 separate light planes. And the way the modules were controlled by the central processing unit (PWM) introduced patterns with fast movements. All these problems ended up showing on the images. The images were good, very colorful, interesting, but not what I had intended. I wanted real-color images.

"Serious Headache", 2014

“Serious Headache”, 2014

In January 2014 I started to redesign the RGB laser modules. This time I decided for a completely new approach. The RGB modules I had used before, emitted a combined point beam and I used one line generating lens for all 3 colors. This was not too successful as all 3 beams had different sizes and actually required different lenses. So I designed a mechanic that would have one lens for each laser and combined the line beams after. This turned out to be rather a tricky business, but it worked. It took me almost 5 months to build these modules and it’s probably the single most expensive piece of photographic equipment I ever invested in. I even bought a 3d printer in order to build them as the mechanics I needed were nowhere available. But it was worth it, the light plane is almost white.

At the time of writing this, Mai 2014, I had the new modules for about two weeks. They are a huge step forward for my LPP work as I am now able to record almost real-color images. But as good as these new RGB modules are, my design proved to have a major flaw: As the three laser diodes in each module create a separate laser line, they are mounted in a distance to each other, this unfortunately introduces shadows with color fringes on the images. Also I was not able yet to calibrate all four modules to have exactly the same tint, as a result some parts of my images have different tints in different regions. Luckily the differences are not very well visible or only in certain situations. And these imperfections give my images a certain character. My main reason to go with this design, that each beam needed a different line generating lens, turned out to be non-existent. I ended up using one size of lens for all colors. You learn as you go…

"Sneaky Hands", 2014

“Sneaky Hands”, 2014. LPP image recorded with my latest RGB modules

There’s enough power to shoot properly exposed pictures while jumping though the wall at moderate ISO. The laser diodes have a nominal combined output power of about 1W although I doubt that more than 300mW are actually ending up in the usable part of the light plane, some of the diodes are tuned down due to calibration and a lot of energy is lost in the line generating optics.

What’s next for me? Many pictures! After almost a year of constructing new machines I finally want to just create images for a while. The new modules open new possibilities, I’m much more flexible from a technical point of view.

An example what it looks like when a model moves through the RGB light plane inside The Reactor:

I’m working on two other projects involving light planes. One is about the creation of sound from light (The Light Sound Project) which is using the unique physical properties of a bright light plane to translate light into sound/noise. Another project aims at creating sculptures of subjects in three dimensional space-time, using light planes to scan subjects. But these are tales for another day…

Did I discover light plane photography? I don’t know. I did lengthy researches and could not find any reference to anything closely related. I’d be very happy if anyone could point me to any work that is related. A lot of the credit certainly goes to Charles Kazilek and William Sharp who have described scanning light photography and who’s article was a strong inspiration.

Next >>: LPP and Laser Safety

Four RGB laser modules lined up for calibration

Four RGB laser modules lined up for calibration

A RGB laser module opened up. The three silver parts are the heatsinks for the laser diodes, on the left are the line generating optics

A RGB laser module opened up. The three silver parts are the heatsinks for the laser diodes, on the left are the line generating optics

The central processing unit for the RGB laser modules

The central processing unit for the RGB laser modules

 

Inside The Reactor

Inside The Reactor

One of my older RGB modules mounted in a corner of The Reactor

One of my older RGB modules mounted in a corner of The Reactor

 

 

 

The Reactor, setup at Tonyraka Art Gallery, Bali, Indonesia in December 2013

The Reactor, setup at Tonyraka Art Gallery, Bali, Indonesia in December 2013

2 comments on “The Story Behind LPP

  1. Pingback: “Number One”, 2011 | jktales

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