dllu (u/dllu) - Readit News

dllu commented on Line scan camera image processing for train photography daniel.lawrence.lu/blog/y... · Posted by u/dllu

stubish · 6 days ago

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.

dllu · 5 days ago

One day I'll muster up the motivation to bring my setup to Roaring Camp to scan those Shay geared locomotives but those moving parts will indeed appear weird and distorted.

dllu commented on Line scan camera image processing for train photography daniel.lawrence.lu/blog/y... · Posted by u/dllu

fooker · 6 days ago

Perhaps some of your noise issues are solvable by using a lens with a large aperture?

Photo finish lenses used to be wildly expensive and sometimes one of a kind.

dllu · 5 days ago

Yeah they have a whopping 300mm f/2.0 lens for photo finish! I have been using various primes including a Samyang 135mm f/2, Voigtländer Apo Lanthar 125mm f/2.5, Voigtländer Nokton 58mm f/1.4, Voigtländer Ultron 35mm f/1.7, Myutron 50mm f/2.6, etc. The problem with a really large aperture is that it's hard to nail focus.

dllu commented on Line scan camera image processing for train photography daniel.lawrence.lu/blog/y... · Posted by u/dllu

fleventynine · 6 days ago

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.

dllu · 6 days ago

I've taken a couple of pics from a moving train...

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.

dllu commented on Line scan camera image processing for train photography daniel.lawrence.lu/blog/y... · Posted by u/dllu

bscphil · 6 days ago

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.

[1] https://github.com/LuisSR/RCD-Demosaicing

dllu · 6 days ago

Yeah I actually have it disabled by default since it makes the horizontal stripes more obvious and it's also extremely slow. Also, I found that my vertical stripe correction doesn't work in all cases and sometimes introduces more stripes. Lots more work to do.

As for RCD demosaicing, that's my next step. The color fringing is due to the naive linear interpolation for the red and blue channels. But, with the RCD strategy, if we consider that the green channel has full coverage of the image, we could use it as a guide to make interpolation better.

dllu commented on Line scan camera image processing for train photography daniel.lawrence.lu/blog/y... · Posted by u/dllu

jeffbee · 6 days ago

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.

dllu · 6 days ago

Thanks, I added a section called "Principle of operation" to explain how it works.

Posted by u/dllu 7 days ago

Line scan camera image processing for train photography daniel.lawrence.lu/blog/y...

Posted by u/dllu 8 days ago

Line scan camera image processing daniel.lawrence.lu/blog/y...

dllu commented on The Barbican arslan.io/2025/05/12/barb... · Posted by u/farslan

pkd · 4 months ago

This was great and the photos were good too!

I have a similar sort of fascination with a structure closer to me: Habitat 67 in Montreal. I have at various points considered buying a unit there but practicality prevents me from doing so each time. I don't know how long I'll resist.

https://en.wikipedia.org/wiki/Habitat_67

dllu · 4 months ago

Thanks for reminding me of this cool building --- I just updated the Wikipedia article with an infobox and a photo that I took in 2019.

Deleted Comment

dllu commented on Helmdar: 3D Scanning Brooklyn on Rollerblades owentrueblood.com/blog/20... · Posted by u/todsacerdoti

weinzierl · 4 months ago

Very cool. When was this? If you would repeat it, which LIDAR would you use? Is there anything on a generous hobby budget nowadays?

dllu · 4 months ago

It was at CVPR 2019, a computer vision conference. I may be biased since I used to work at Ouster, but cost notwithstanding, I would definitely pick the OS1 again for its unparalleled number of points per second combined with low weight and decent accuracy.

u/dllu

KarmaCake day1437January 13, 2012

About

http://daniel.lawrence.lu

View Original