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Posted by sebg 1/1/2026

Cameras and Lenses (2020)(ciechanow.ski)
549 points | 57 commentspage 2
brcmthrowaway 1/1/2026|
Does anyone know of a lens that can make a laser look like a spotlight?
dekhn 1/1/2026||
More details required.

Like the other comment says, this can be done with a beam-expanding telescope (which can be as simple as two lenses whose focal length ratios determine the magnification). https://www.newport.com/n/how-to-build-a-beam-expander and https://www.thorlabs.com/an-example-of-a-diy-keplerian-beam-... are a good place to start.

But it can be a bit more complicated than that , and it's often easier to use an LED.

aj7 1/1/2026||
Look up “beam expanding telescope.”
ChrisMarshallNY 1/2/2026||
This guy's stuff is always so awesome.

Thanks for sharing it!

fluorinerocket 1/2/2026||
Awesome, I learned something about optics! I was afraid this was going to be about Haskell
behnamoh 1/1/2026||
Can we donate to creative individuals like the OP so they keep making amazing stuff? This is the kind of output LLMs will not be able to produce any time soon.
macintux 1/1/2026||
He has a Patreon: https://www.patreon.com/ciechanowski
sho_hn 1/1/2026||
"Make a Bartosz-style website about $topic" seems like a fun benchmark idea. Maybe more so than pelicans on bicycles.

To be honest, though, this seems like ideal content for an LLM to produce. It's basically fact regurgitation.

dpark 1/1/2026|||
> It's basically fact regurgitation.

This page wasn’t a regurgitation of facts. It was filled with custom interactive applets that let you explore the effects of physical changes. The core value proposition here is not the facts but the ability to explore and intuit the physics.

sho_hn 1/1/2026||
I do understand the contention is that an LLM would be less thoughtful in editorializing which bits to make interactive, reasoning about the progression in understanding and delight by the user.

I'm not so sure it's that far out of reach, though. From what I've seen the reasoning models do, they're not too far away from being able to run a strategy of figuring out interesting increments of a problem, parameterizing them, making an interactive scene for those parameters, ... it feels within reach.

dpark 1/2/2026||
I said nothing about LLMs. I said this page was not simply regurgitation of facts.

I personally doubt LLMs are close to producing anything like this, but that wasn’t the point. You indicated that this should be easy for an LLM because it’s just a fact dump. Regardless of whether some future LLM can generate something like this, it’s much more complicated and interesting than a simple fact dump.

morning-coffee 1/2/2026|||
> To be honest, though, this seems like ideal content for an LLM to produce. It's basically fact regurgitation.

You're trolling us, right? "Basically fact regurgitation" is all that teachers do after all. Have you ever noticed the difference between an inspirational teacher and a not-so-inspiring one in terms of effectiveness of communication and the "ah ha!" or lack of moments in your own understanding? If you can honestly say "no", then I might be able to understand your statement above, but really?

w0m 1/2/2026||
TBF; the infamous MS report 'Working with AI: Measuring the Occupational Implications of Generative AI' had Teacher/Professor pretty high up there.
Yaggo 1/2/2026||
The content is gold but so is the web page design.
_jayhack_ 1/1/2026||
Great article. For another fantastic explainer on optics, see 3Blue1Brown's video on refraction: https://www.youtube.com/watch?v=KTzGBJPuJwM
pontussw 1/1/2026||
This is so incredibly well done
ChrisArchitect 1/1/2026||
(2020)

Some discussion then: https://news.ycombinator.com/item?id=25357315

andyfilms1 1/1/2026||
Doesn't seem to work in Firefox. :(
uhoh-itsmaciek 1/1/2026||
FF on Android seems to work fine here. What problem are you seeing?
yazide 1/1/2026||
[flagged]
mcdonje 1/1/2026|||
Works fine for me with Firefox on Debian. Are you sure you don't have an extension breaking it?
fsckboy 1/1/2026|||
I use firefox with javascript mostly off (UMatrix) but when I turned it on for fonts.googleapis.com the site and sliders all seem to worke. then I turned it on for gstatic.com fonts.gstatic.com , and not sure if that changed anything else. I'm on linux desktop
cfraenkel 1/1/2026|||
Also works in Firefox (144.0.2) / MacOS (10.15)
compiler-guy 1/1/2026||
Working fine on Firefox for IOS.
unit149 1/1/2026|
[dead]
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