I’m referring to those old black and white videos of US atomic bomb tests – it always shows buildings and other constructions being literally blown away but the camera seems fine
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The camera is really, really *really* far away, and really really really zoomed in. And it is behind protective glass.
So the test footage you are referring to is vary famous. And the answer is less appealing than you want unfortunately. Multiple constructions were made to test and demonstrate the effects of Shockwaves and searing heat. You can even find some footage from inside the buildings durring the detonation. The answer as to how the cameras survived is because they were built inside of proper bunkers instead of the wood houses meant to demonstrate suburban areas at the time. If you oay close enough attention, in some of the footage you will see the houses begin to combust before the blowing Shockwave hits them. Vary hot. But not enough to melt glass at that distance.
TLDR: wooden demonstration houses weak. Concrete camera bunkers not.
It’s inside a small, very rugged and securely anchored enclosure. They’re far enough from the bomb that the explosion is at the scale of “searing heat and sudden hurricane”, and not in close where everything is melted to glass or crushed to dust.
Some are also very far away but with a good zoom lens.
There are a few different ways they did this. A lot of the footage was shot through mirrors to protect the camera. Just like a periscope protects soldiers in trenches. They also commisioned special cameras where the film were routed into a safe to protect it when the camera got destroyed. They still lost a lot of footage.
Mirrors and bunkers.
The camera does not need to be exposed to the shockwave it only needs to receive light from it. So one simple way is to have a concrete bunker with a mirror on top that gets blown away but the camera is safe inside like in [https://twitter.com/BraumLincoln/status/1257553592527060992/photo/1](https://twitter.com/BraumLincoln/status/1257553592527060992/photo/1)
That can be used to capture the explosion but film like the building where the camera is clearly close to the explosion. That it is closer it the key which meant the camera can look away. So build a bunker, that do not have a flat side toward the explosion but an inclined surface, it can simply be a pile of dirt again the back wall. The camera looks out the back away from the blast.
Look at a munition bunker-like [https://c8.alamy.com/comp/J59EGH/weapons-storage-bunkers-J59EGH.jpg](https://c8.alamy.com/comp/J59EGH/weapons-storage-bunkers-J59EGH.jpg) the concrete wall would point away from the explosion and you have windows that the camera points out at through it. The shockwave will hit the inclined area on the other side.
House films have a camera quite high up, So you might not build a bunker just like that but use the same principle and build a concrete structure that does not have a flat side towards the bomb but an inclined surface. You know where the blast is common from so a structure a bit like the tail fin of an airplane can provide low surface area toward the blahs but a lot of material to handle the blast.
The house video shows a wooden building being blown apart. Wood is a lot weaker than concrete so building something that can handle the blast is not that hard. Test [https://nuclearsecrecy.com/nukemap/](https://nuclearsecrecy.com/nukemap/) with a surface detonation.
There is a Heavy blast damage radius (20 psi) described as
>At 20 psi overpressure, heavily built concrete buildings are severely damaged or demolished; fatalities approach 100%. Often used as a benchmark for heavy damage in cities.
Moderate blast damage radius (5 psi)
>At 5 psi overpressure, most residential buildings collapse, injuries are universal, and fatalities are widespread. The chances of a fire starting in commercial and residential damage are high, and buildings so damaged are at high risk of spreading fire. Often used as a benchmark for moderate damage in cities.
The building we see is wooden so the pressure might be around 5 psi. compare that to 20 psi for heavily built concrete buildings, that is buildings of the types that exist in cities, not a bunker you build to handle nuclear blasts. You can build bunkers so you need a direct hit on them to take them out. Direct might be an exaggeration but let’s say inside the fireball the bomb creates. A wall can be meters thick with reinforced concrete, and the shockwave at the distance the building it recorded will not damage a wall like that.
The camera is far away, in a small concrete bunker, with a telephoto lens, filming through a thick window.
Type “camera bunker atomic tests” into Google Image search for pictures.
In nuclear weapons testing, the shock and blast for above ground nuclear weapon tests were generally estimated and allowed for the experiment designers to place both “sacrificial” sensors and equipment (like cameras) in areas they knew were going to be destroyed, and regular equipment that was outside the projected blast radius.
In other tests, special bunkers or shelters were used to mitigate shock and blast effects of the detonation. In both cases the units storing the footage were either projected to survive (and did), or had reinforcements on the unit storing the footage to mitigate both blast effect and radiation effect damage.
Many of those films were of carefully constructed buildings to represent “average” construction of various types, specifically for the testing. The cameras were located in bunkers in the test area, protected from blast and radiation, filming through periscopes through armored glass. Even if the blast destroyed what was above ground, the film would survive in the camera mounting pit.
Lots of good answers here but i want to point out something that people don’t always realize. Nuclear blasts are not quite as powerful as perhaps sci-fi has lead us to believe. Play around with that website Nukemap. A large portion of the damage from nuclear weapons is simply heat that starts fires. They don’t literally vaporize cities. Even the largest H bomb thermonuclear weapons in our arsenal would only truly vaporize about 1.5 mile radius. Outside that 1.5 miles you get blast damage to 10 miles but that is easy to protect a camera from. And again, that’s our biggest ICBM nuke (according to Nukemap anyway) most of them are much smaller and the ones in the videos may have been smaller still.
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