Introduction: Abakography: Long Exposure Photography That Mimics Human Vision
Top picture: Floor lamp sliding back and forth; long exposure photography done right!
Bottom picture: Bug sweeper waved back and forth reveals microphone's capacity to eavesdrop. Loudspeaker emits a test tone, and a lock-in receiver picks up even the weakest of signal transmissions and outputs to an attached SWIM (Sequential Wave Imprinting Machine) that displays audio "metasensing" waveforms.
Long-exposure photography done right!
In this Instructable I present 8 simple steps you can use to mimic human vision and capture a true and accurate picture of a light source that is being waved back and forth.
The result is a sequence of exposures that can be combined (9th step) into a single .gif image that shows the back and forth motion nicely.
This is the sequence of steps I've developed over that past 42 years (originally back in the days of film, to make "flip books" of pictures that show light trails in long exposures of a linear array lights I made to see radio waves, sound waves, etc.).
Once you get the hang of it, it is quite quick and simple to do.
This method can then be applied to phenomenal augmented reality as in my previous Instructables.
Begin with a light source such as the augmented reality wand you made from one of my previous Instructables, or simply a light bulb or candle or anything else that glows.
For best results, use a camera with manual exposure settings.
A camera flash helps fill in the details, and you get a nice "flash and blur" effect. The following steps assume you have the more common first-curtain flash sync (you can easily adapt to second curtain sync if that is what you prefer).
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Begin
Locate a dark space where the lights can be turned off. Here we are using a light bulb in a dark classroom. Choose a dark black background ("blackground") for best results. Here the blackground is the blackboard. It can also be a large open dark space, or you can hang a "blackdrop" (e.g. a black backdrop cloth)....
Identify a beginpoint and an endpoint. Mark these with objects that the subject can easily see in the dark (e.g. see by only the light of the lamp), or by objects the subject can feel. Here we use the two ends of a chalkboard that the subject can feel by running his fingers along the chalk trough, in this example.
Here a camera on a tripod is set to "B" ("Bulb") and a remote control is used to activate it so as not to shake the camera: remote activation means we can actuate the shutter without pressing on any of its buttons which would shake it and perhaps make the exposures blurry or misaligned.
Before you turn off the lights to "Begin", you might want to take one or more pictures with the lights still on, and then turn the lights off and take one or more pictures of the dark (no flash) to characterize the ambient light in the scene. You can use these for advanced image processing (e.g. to model the background statistics of the light in the room, analogous to a "room tone" audio recording). I call these a1.jpg, a2.jpg, a3.jpg, ... ("Ambients").Begin
Have the subject stand at the beginning position holding a light source. Here the subject is holding a light bulb plugged into a light dimmer and turned down really low. I like to use a reasonable size light bulb like a 750 watt, 1000 watt, or 1500 watt light bulb dimmed down to a really low brightness, so we can see the intricate details of a nicely sized bulb and nicely sized filament.
While the subject stands still, take a picture of the subject holding the light.
Sometimes I take multiple "Begins" and assign them filenames like b1.jpg, b2.jpg, b3.jpg and pick the best one, or use more than one if you want your exposure .gif file to ultimately "dwell" at the beginpoint for longer.
Step 2: Centrails (Central Trails of Light)
Have the subject move forward about 1/4 or 1/3 of the distance along the trajectory of the path. Instruct the subject to move backwards to the beginpoint as soon as the flash on the camera fires.
Press the camera shutter release remote button, and hold it down: The flash should fire at the beginning of the exposure, and as you keep the button held down, the exposure will continue, as the subject walks backwards to the beginpoint. When the subject reaches the beginpoint, let go of the shutter button.
Now you have your first "Centrail" (Light trail picture from a central point along the trajectory).
At a minimum you need at least one Centrail, which you can take at the exact midpoint, but ideally you want 2 or 3 Centrails, e.g. at the 1/3 and 2/3 point, or at the 1/4, 1/2, and 3/4 point.
Start with short Centrails and work your way to longer ones.
I usually name these as follows:
c1.jpg (first 1/3 or 1/4 and then back to the beginpoint);
c2.jpg (e.g. midpoint or next third back to the beginpoint);
c3.jpg (from 3/4 of the way back to the beginpoint).
Step 3: Destrail (Destination Trail of Light)
Take at least one exposure where the subject walks backwards from destination to beginning.
You press and hold the shutter remote button.
The subject starts at the finalpoint (endpoint), and when the flash fires, walks back to the beginpoint. When the subject reaches the beginpoint, you let go of the shutter button.
Step 4: Easementrails
Once you reach your final destination, you now want the light to "ease off" gently.
For each of the "Easementrails" (easement trails) have the subject stand at the final position, and each time, move backwards after the flash fires. Easementrails should go from long to short, so they appear in the correct order.
Have the subject walk backwards 3/4 of the way after the first flash.
Then take another picture and have the subject walk 1/2 way back for the second picture in the Easementrail set.
Then take another picture and have the subject walk 1/4 of the way back.
You can label these as filenames e1.jpg, e2.jpg, and e3.jpg.
Step 5: Finalposition
Take a picture while the subject remains still at the final position.
Next we are going to have the subject moving back toward the initial position, thus completing the loop from beginning to finalposition, back to beginning.
Step 6: Goback Trails: Going Back to the Initial Position
Next come the "goback" trails, where the subject works his or her way back to the initial position.
For the first goback picture, have the subject begin 3/4 of the way across, and go to final position when the flash fires. Call this g1.jpg
Then have the subject begin at the 1/2 way point, and go all the way to final position when the flash fires. Call this g2.jpg
Have the subjects begin at the 1/4 way point, and go all the way to final position when the flash fires. Call this g3.jpg
Step 7: Holding Trail
Have the subject start at the beginning position, and then after the flash fires (while the exposure continues) go to the final position.
Call this h1.jpg
Step 8: Intermediatrails (Intermediate Trails)
Have the subject start at the 3/4 position and wait for the flash to fire and then go to the initial position while the exposure is being made. Call that i1.jpg
Then have the subject at the mid point and when the flash fires go to the initial point. Call that i2.jpg
Have the subject stand at the 1/4 point for the flash to fire and then walk to the beginning point during the continued exposure. Call that i1.jpg
Step 9: Combine the Exposures Into a Single .gif Picture
Above pictures: Light bulb, a row of LEDs and, rightmost, waving feedbakographic light source in front of a box reveals the sightfield of a pinhole camera hidden inside it (picture I took of a student's project based on one of my previous Instructables).Summary of the steps to abakography:
In summary, you will have created the following files:
- a1.jpg, a2.jpg, a3.jpg (Ambient) These are optional. You can also start directly at Beginning and skip these!
- b1.jpg (Beginning)
- c1.jpg c2.jpg c3.jpg (Centrails)
- d1.jpg (Destrail)
- e1.jpg e2.jpg e3.jpg (Easementrails)
- f.jpg (Finalposition)
- g1.jpg g2.jpg g3.jpg (Goback trails)
- h1.jpg (Holding)
- i1.jpg i2.jpg i3.jpg (Intermediatrails)
- j1.jpg (Joinback). This is optional. At the very end you'll end up at the same place as the beginning. You can call this j1.jpg or you can simply call it b2.jpg since it is basically the same thing as Begin.
I have chosen the filenames to sort alphabetically, e.g. with consecutive letters of the alphabet.
Thus you can combine them with the single "convert" command in a UNIX or GNU Linux shell, as follows:
convert -resize 1200x [b-i]?.jpg out.gif
Now your long exposure picture is in file "out.gif"
It should provide you with a natural looking picture of approximately what the human eye sees.
We're working on developing new photographic camera systems that mimic human vision automatically so you can take pictures like this by just pushing one button, and also take video like this automatically.
For further research on abakography, see: