I now have a Discord server: discord.gg/B6uNzAgshy Come and say hi. The sponsor is Henson. Get 100 free blades with your first safety razor: hensonshaving.com/stevemould use code stevemould

the transition from the goofy shaving sequences to the horrible business model of printers to the sponsor was amazing

I love how you can clearly see Steve getting more and more giddy with this shaving bit as the video goes on.

I cannot believe that I didn't see the changes in your facial hair until the half-way point. The strange feeling I got, once I realized it had been happening already and I'd been missing it, will be my main takeaway from this video. And the concept of caustic lenses will probably be floating around there somewhere too... but certainly not as palpably.

That. Is how you make a UKposts video. Take notes people. This man. This man right here.

Loved how the shaving starts off subtly and gets progressively more. Way to go, all in for a sponsor. Hope they appreciate you.

Caustics are also one of the hardest problems in computer graphics, because light from anywhere in the scene might just end up on one of those bright lines, so you have to simulate a ton of light rays to get a noiseless image.

A1 video Mould. I’ve been subscribed since at least the 10th grade (im 25 now) and I can tell you that I’ve noticed how your videos have gone from purely informative to informative and genuinely entertaining. Feel like you’ve come into your own shoes in the UKposts sphere. Can’t wait to see what you got cooking next man. This is one of the best educational channels on this site.

Bro the gradually shaving your beard throughout the video melted my brain.

You integrated the sponsorship so well and without interrupting the video that I watched the whole thing at the end out of curiosity and respect. Very well done!

1:11 - that's one of the most beautiful things that exists in my opinion. Since I was a kid I always were mesmerized by those lights under the water.

4:18 this is so cool, I would love to see something like a scaling medieval landscape with a castle or something but instead of it being thru the thin edge, carve it so if shine light thru it sideways you get a long flat artwork

I know I probably will never NEED half of the knowledge I gain from this channel but I still look forward to it. I love learning about random things like this. Love this channel.

At EPFL (where the Alan Turing image comes from) there are a few of those acrylic panels under the library so that when sunlight shines on it, faces of famous people show up on the ceiling. Pretty impressive "resolution" too when the light shines just at the right angle

Man.. The gags that Steve has for his first video of the new year always get me. Between his ballerina act last year and the disappearing beard gag this time, it makes me wonder if the family he visits during the holidays are all buttoned down people who don't respond to his humor, and he just has to let it all out afterward?

What a cool idea for an episode and very well done. Very fascinating. Bravo

Finally! I've been waiting for this follow-up!

I'm curious how they actually make these peices of glass.

Half beard Steve is not real, it can't hurt you. Half beard Steve: 3:48

visually encoded shaving transform is a nice touch and proves production & editing skills.

The most impressive part is seeing the black areas, you'd just expect the non-lit sections to be the same as the loght passing through flat glass. Seeing that immense contrast is so cool!

I absolutely love the creative approach to the ad read. We are so used to skipping over ads because they are just written by a company who is paying the creator to read a script. When a creator spends the extra time and effort to make the ad their own with a creative twist or spin on the ad read it really makes you want to watch the ad! Not because it’s an ad but because now it is content form the creator who you are there to watch in the first place.

smooth transition 🙂Also - the pattern made by those lenses when turning, reminded me of video waveform monitors.

Thank you! Your videos always brighten my day. Then in top of that, I learn something new.

I can't help but notice how the reflections look just like a video waveform monitor when light reflects from them at a narrow angle, I think it is a good analogy for how they work

Love how you carried the sponsor all the way through for a reveal at the end. Just like the light shining through the glass reveals the lion. Brilliant!

Good job on the sponsorship spot! It did make me want to try a safety razor and I like well engineered items. I'd have been willing to pay £30 for the handle, but nearly £60 is too rich for me.

Imagine having this guy as your physics teacher

Steve you're missing half your beard

3:48 his beard is half gone but it’s all there in the shot before Edit: it gets worse throughout the vid

The way you introduced your sponsor is so awesome!

Okay but that business card one from the beginning is genius-

Wait a damn second! 5 minutes into the video and I only just now notice that half his face is shaved? Am I missing something? XD Btw great video so far. Edit: okay the shaving is progressing as the video goes on... I am THOROUGHLY confused xD

Noticing half the beard gone at 3:49 really shocked me. Had to go back to make sure it wasn't gone from the beginning!

That subtle smile, you know what you are doing with your beard. Bravo!

I love that you are holding back laughter in every cut where you're partially shaved.

That must've been so difficult to not laugh during the parts with the beard transitions.

you can start a fire using water as a lens! you just need pretty clear water and a lot of direct sunlight. there are a few different ways to make it work, but a ziplock bag full of clear water might be the easiest. i've also seen a regular water bottle do it with a lot of patience

Great video and yes Henson razors are awesome. Switched from cartridges a year ago and love the smooth shave and cost savings knowing that blades cost only $0.10. I usually get about 5-7 good clean shaves out of one.

Nice plug for the safety razors :) I use one from the 50's, the plating is a bit worn but works just fine.

What an ingenious lead in to the sponsorship. the whole video I'm like "okay... he's surreptitiously losing more and more facial hair every time it cuts back to him. wtf is going on?"

I'd love to learn about the deeper maths behind the optimum transport problem!

The video is great as always, but man do i want one of those razors now, what a beauriful integration!

Your 1/2 Five O' clock shadow hologram is very convincing! Super cool! Great video!

IIRC the optimal transport problem prompted a matematichian to make the first nomograph , wich is a printed analog computer composed of lines with numbers on and it's meant to be used with a string or a ruler , I reccomend checking them out because they are pretty awsome

Nice shaving transition! I didn't notice until 6:00, lol.

"Once you know that you want 'hair' from your beard to go there..." Loved the explanation as always! Steve is an amazing teacher who has mastered the art of explaining difficult concepts in a fun n engaging way. You rock man!

I've seen a similar thing before concerning images having depth, the Kodak film 'Kodachrome' had layers which were said to improve the image - it was an extremely complex and therefore expensive developing process that was abandoned decades ago.

Amazing explanations, thank you

Man. This is possibly only time that a sponsorship in a UKposts video has me sold on the spot.

This is your best work so far Steve. It could even be the greatest UKposts video ever made. Theme, explanation, advertising tease, all perfectly executed. You could also have mentioned that the razor blades involve no plastic waste, which was my main reason for buying a similar competitor that I won't mention for obvious reasons.

Great video. I am working in a closely related field. If you do X-ray Nano-Imaging you have to solve the exact opposite you problem, you measure one of those smeared-out patterns where you can guess the coarse shape of the object, and your goal is to find the density of the object (your sample in the microscope) that has produced the pattern you observe. Mathematically it is almost identical. The more technical term for this is X-ray Inline Holography.

So weird! I haven’t seen this particular video till now even though I’m subscribed. I didn’t notice the shaving thing till 4:50. I had to rewind and watch it from the beginning to see the progression. This just messed my brain up! How did I not notice? lol

THANK YOU! FInally! some good explainer on controlling caustics. I really wish The Rayy would make a software that could make these virtually, or even better a depth pattern for cutiong out of metal

I love when people cover new technologies such as this one that I didn't knew existed! Here is another recent technology that may interest people here : Cypris Materials has created polymer pigments, that while colorless when dry, turns to any color of the spectrum once applied as a paint. They work based on structural colors the same way as opals do. They have a few videos on UKposts, they are worth watching!

oo i've actually thought about this tech a few years back, how it could be used in lamps in a room to direct the light to more efficiently (and more prettily) illuminate the room

Well done integrating the sponsorship. Interestingly safety razors seem to be making a comeback on multiple fronts. As a decades long user of classic safety razors I applaud this an find it amusing at the same time. Feels a bit like being smug and saying „ah, finally… Took you long enough“. I was also fed up with the cost for the cartridges. Their only upside really is that you can usually put cartridges 😅into carry-on luggage if you happen to fly.

You can also make that shape in coffee mugs by rotating a two circles of different diameters connected by a single point on each of their circumferences. The mug version has an exact ratio of 2:1 for the smaller and larger rings respectively. I can post images of several that I created a couple of years ago if you want to see some examples.

I always look forward to these video, thank you Steve!

An ad so well executed, I wish the usual sponsor blocks were more like this

I absolutely stayed and watched the entire sponsor segment because I was super curious. Well played

No one noticed his beard disappearing.🤣🤣🤣

i was sitting by the pool today and i literally thought about the ripples that are caused and i thought about it and when i figured it out my first thought was "huh, could be a steve mould video" love your videos man!

The mention of Optimal Transport made me realise that there must presumably be an infinite number of Suboptimal lenses that produce an identical image.

Curious...and alarming! (and EXCELLENT tie-in for Henson!!! Well done!!!)

6:48 Everyone pauses to do a web search

Interesting , Steve; it reminds me of the moiré fringe effect. I have always thought it would a fine idea if the bridges of motorways have the spacings of their grills altered so that, just at the right time, the moiré fringe spelt out something: 'Drive carefully', for example. The maths is well beyond me, but maybe the two ideas are related?

Love the creativity of the sponsor implementation

Closest thing to this I've experienced is the Camera Obscure effect caused by my window shades. They're blackout style, but not true blackout, as the edges still let some light by. It's those edges that create the lens... So when my mom is walking outside around the side of the house near my bedroom, I'll see her shadow get projected along the wall where that light is shining through. Or, the vehicle at it drives around the driveway. Obviously, though, everything is upside down.... But it's still every bit recognizable. 😊

Great video, I’ve always been fascinated how you can manipulate projections of transparent 3d objects, seeing all the details magnified on a wall or something. Basic lenses lol.

My 6yo, 8yo, and I love your videos!! Thanks so much for sharing fascinating science to all ages!!

Ohhh, how awesome your channel is, I want this show on tv!

Hi Steve, what always mesmerises me is the steady transition between the visible image and the chaotic light. Isn't that - like with every lens - the steady fourier transition?🤯 I have been wondering since my bachelor if there's any usable information in that.

0:01 hi timed

These are beautiful, thanks for shaving Steve!

I normally like your videos, but the way you presented your sponsor was GOLD. I 💯 support Henson already, but that just sold me all over again

FWIW - I tried a ton of safety razors this spring and Henson is the best. Rad to see them sponsoring your video. It's so rare to see a product sponsor a content creator ... and the product is actually great! Go buy a Henson, do it now!

What's wild is those Japanese "magic mirrors" that were crafted by hand hundreds of years ago that do something similar. They were created when Christianity was banned in Japan. It worked like a normal mirror but could also reflect an image of a cross in sunlight.

I can confirm, safety razors are great. I bought one a few weeks ago for €20, you can get a pack of 100 blades for €0.10 a piece, and they actually shave _better_ than a conventional razor! Although it is also easier to cut yourself if you're not careful. This was actually the first time I cut my legs while shaving. Ouch. But you can also take them apart to get the hair out! So great!

This definitely is related to the extended depth of field lenses for cataract patients and/or presbyopia correction....🤔

I really thought a Fourier transform was going to be involved. I swear I learnt that at uni, maybe with lasers.

Never seen such an immersive endorsement of a shaving razor .

I was once in the quality control department of a company that produced optical mark reading machines best known for test scoring. They sometimes used the Razor and Blades model. Sometimes we would give the customer the expensive machines for free if they bought enough forms to run through them. The forms are printed with special inks that are visible or invisible to the machines but not to humans.

🎯 Key Takeaways for quick navigation: 00:00 🌞 Caustic lenses can produce recognizable images by manipulating lens shapes. 01:03 💧 The patterns caused by undulations in transparent materials are related to how lenses work, focusing light rays to create bright lines called caustics. 03:00 🔍 Shaping lenses to redistribute light optimally is an area of mathematics known as optimal transport, akin to sculpting sand with minimal movement. 04:27 🌐 Power diagrams represent the distribution of light, and adjusting them influences the brightness and darkness of regions in an image. 05:53 🖥️ Computer scientists like Mark Pauly have contributed to understanding and implementing the curvature of lenses to create specific images. 06:51 🌈 The transition from familiar light patterns to recognizable images in these lenses creates visually engaging moments. 08:16 💼 The video sponsor, Henson, makes well-engineered safety razors, providing an alternative to the expensive "razor and blades" business model. Made with HARPA AI

I always wanted to use things like this on that Glow In The Dark paper, to "store" the image

I didn't notice the beard until 4:55.

This video was smooth in SO MANY WAYS The main topic flow The beard The printer to razor Segway the end

Interesting video! I’d always thought they’d be similar to diffraction patterns, which are the Fourier transform of the diffraction grating. But it looks like the maths is much more complicated with caustics.

Was waiting for this video, ever since I found the research done at EPFL I am fascinated - love to all the light enthusiasts out there! ✨

@6:53 is that a pull back or is he just circumcised?

In the late 70's, mid 80's - photographic lens manufacturers were smashing their brains trying to make aspherical lenses (basically, a compound spherical curvature, useful for correcting certain aberrations). Those lenses ended up being ridiculously expensive, in difficult design/construction processes. Only a few years ago manufacturing techniques have allowed aspheric lenses to be a bit more common. Caustic lenses would simply blow the minds of the optical designers of the 70-80s

Safety razors are fantastic! Nice work on the sponsorship!

Re: printers, a decade or so ago I looked into the numbers and saw it was legitimately cheaper to buy a brand new printer than to buy all new ink cartridges, and I did that a few times, giving away or selling the now inkless printer for extremely cheap. I've now got one that can use third party/refillable ink cartridges that are priced reasonably (there are plenty that will detect the non-brand-name cartridge and refuse to operate!) and it's a good printer that doesn't hassle me, too :) Still hate printers, though.

The beard has been a fucking trip

Best sponsorship bit on youtube period. Awesome vid as always but as a lifelong electric shaver guy I'm genuinely tempted to get one of these just to support the business model

3:51 I like the Half beard cut, great new style!!!

If someone out there still hasn't switched to safety razors, you have to give it a go. They really are better once you get used to holding the different shape. They are more environmentally friendly, and the replacement blades are dirt cheap. My favorite part about safety razors is that you can take out the blade and rinse off any hairs that get stuck in gaps.

Always enjoy Mould's playful approach to STEM.

I remember back in the day my dad showing me how to make holograms by hand with a pair of compasses on sheets of acrylic. I got pretty good at it. It's not just the skill in scratching them into the plastic, it's in choosing a subject that translates well to the medium.

I have seen the designed mirror reflections, some are very antique religious artifacts. Very artistic treasures.