Okay I was stumped about how this works because it's not explained, as far as I can tell. But I guess the sensor array has its long axis perpendicular to the direction the train is traveling.
IMO the denoising looks rather unnatural and emphasizes the remaining artifacts, especially color fringe around details. Personally I'd leave that turned off. Also, with respect to the demosaic step, I wonder if it's possible to implement a version of RCD [1] for improved resolution without the artifacts that seem to result from the current process.
It's neat that it captured the shadow of the subway train, too, which arrived just ahead of the train itself. This virtual shadow is thrown against a sort of extruded tube with the profile of the slice of track and wall that the slit was pointed at.
Super cool. I wonder if you could re-use a regular 2-d CMOS digital camera sensor to the same effect. But now I realize your sensor is basically 1-D and has a 95khz sampling rate. At the same rate with a 4k sensor you'd have way too much data to store and would need to throw most of it away.
Pretty sure could do it but it would be very expensive, because you'd need alot more very fast ADCs.
Like if the camera is $5k, in order to get that exposure time in full-field you would need to duplciate the hardware 800 times or whatever you wanted horizontal resolution to be. Thats alot of zeros for a single camera
Fun read! I used to work in sensor calibration, and most people take for granted how much engineering went into having phones taking good photos. There’s a nontrivial amount of math and computational photography that goes into the modern phone camera
Iirc, at the last Olympics, Omega paired a high-frequency linear display with their finish-line strip cameras. Regular cameras saw a flashing line, but the backdrop to photo-finishes was an Omega logo. Very subtle, but impressive to pull off.
I looked into line cameras for a project. I think their main application is in quality control of food on conveyer belts. There are plenty of automated sorting systems that can become a bottleneck. One of the units I speced out could record an 8k pixel line at up to 40kfps.
They are used in OCT (optical coherence tomography) as well
OCT is a technique which uses IR to get "through" tissue using beam in the near infrared (roughly 950 nm, with a spread of roughly 100 nm). The return is passed through interferometer and what amounts to a diffraction grating to produce the "spread" that the line camera sees. After some signal processing (FFT is a big one), you can get the intensity at depth. If you sweep in X,Y somehow, usually deflecting the beam with a mirror, you can obtain a volumetric image like an MRI or sonogram. Very useful for imaging the eye, particularly the back of the retina where the blood vessels are.
Does anyone know what it looks like when you use a line scan camera to take a picture of the landscape from a moving car or train? I suspect the parallax produces some interesting distortions.
Sorry for the purple trees. The camera is sensitive to near infrared, in which trees are highly reflective, and I haven't taken any trains since buying an IR cut filter. Some of these also have dropped frames and other artifacts.
I love this! I tried to apply the same idea to scan the tallest tree in New England with a drone. It didn't come out great, but I might just try again now.
Anyone know of a steam train captured in the same way? I'm interested in the effect of the parts with vertical motion such as the pistons and steam clouds, combined with the largely static body.
I have been creating animations using a similar process but with a regular camera and manually splicing the frames together. [1,2,3] The effect is quite interesting in how it forces focus on the subject reducing the background into an abstract pattern. Each 'line' is around 15px wide.
I also shot a timelapse of the Tokyo skyline at sunset and applied a similar process [4], then motion tracked it so that time is traveling across the frame from left to right[5]. Each line here is 4 pixels wide and the original animation is in 8k.
48 comments
[ 3.7 ms ] story [ 65.7 ms ] thread[1] https://github.com/LuisSR/RCD-Demosaicing
Probably would be worth asking a train driver about this, e.g. "what is a place with smooth track and constant speed"
Must be somewhat interesting deciding on the background content, too.
Like if the camera is $5k, in order to get that exposure time in full-field you would need to duplciate the hardware 800 times or whatever you wanted horizontal resolution to be. Thats alot of zeros for a single camera
https://youtu.be/E_I9kxHEYYM
OCT is a technique which uses IR to get "through" tissue using beam in the near infrared (roughly 950 nm, with a spread of roughly 100 nm). The return is passed through interferometer and what amounts to a diffraction grating to produce the "spread" that the line camera sees. After some signal processing (FFT is a big one), you can get the intensity at depth. If you sweep in X,Y somehow, usually deflecting the beam with a mirror, you can obtain a volumetric image like an MRI or sonogram. Very useful for imaging the eye, particularly the back of the retina where the blood vessels are.
You can get some cool distortions at very slow speeds, but at car or train speeds you won’t see anything
Nankai 6000 series, Osaka:
https://i.dllu.net/nankai_19b8df3e827215a2.jpg
Scenery in France:
https://i.dllu.net/preview_l_b01915cc69f35644.png
Marseille, France:
https://i.dllu.net/preview_raw_7292be4e58de5cd0.png
California:
https://i.dllu.net/preview_raw_d5ec50534991d1a4.png
https://i.dllu.net/preview_raw_e06b551444359536.png
Sorry for the purple trees. The camera is sensitive to near infrared, in which trees are highly reflective, and I haven't taken any trains since buying an IR cut filter. Some of these also have dropped frames and other artifacts.
Here is how it came out: https://www.daviddegner.com/wp-content/uploads/2023/09/Tree-...
It was part of this story: https://www.daviddegner.com/photography/discovering-old-grow...
[1] https://youtube.com/shorts/VQuI1wW8hAw [2] https://youtube.com/shorts/vE6kLolf57w [3] https://youtube.com/shorts/QxvFyasQYAY
I also shot a timelapse of the Tokyo skyline at sunset and applied a similar process [4], then motion tracked it so that time is traveling across the frame from left to right[5]. Each line here is 4 pixels wide and the original animation is in 8k.
[4] https://youtu.be/wTma28gwSk0 [5] https://youtu.be/v5HLX5wFEGk
Photo finish lenses used to be wildly expensive and sometimes one of a kind.