The Gizmodo images are the older Brijot passive scanners that look like this: https://sm.asisonline.org/ASIS%20SM%20Article%20Images/10-120-02b_0.jpg https://sm

The Gizmodo images are the older Brijot passive scanners that look like this: https://sm.asisonline.org/ASIS%20SM%20Article%20Images/10-120-02b_0.jpg https://sm.asisonline.org/ASIS%20SM%20Article%20Images/10-12... Passive can also do high resolution[1]. It depends heavily on the wavelength being measured. Your second link is talking about far infrared (300+ GHz), or close to. Those waves are blocked more by clothing compared to the <100 GHz (30 GHz?) that Brijot and the current scanners use. The high frequency stuff will show a dark spot where something may be hidden, but is very dim compared to active scanners. They have similar resolution but are much blurrier. Passive scanners at 30 GHz are by necessity lower resolution at the same price point, because the human body doesn't emit too much around there. However since all the waves are coming from the body, anything hidden under the clothing will block the waves completely and show up as an obvious dark spot. You don't need detail because of that. Active scanners on the other hand are super detailed, again by necessity. That wavelength goes straight through clothing but since waves are being produced by the machine, anything besides metal will look basically the same as skin. You need to be able to make out the shape and texture to identify it, so the sensors are very high resolution. They need to see the trigger of a gun to know it isn't just a weird rectangle, so that means they can also see your foreskin. [1]: http://www.homelandsecuritynewswire.com/sites/default/files/imagecache/standard/passmill-1.jpg http://www.homelandsecuritynewswire.com/sites/default/files/...