Debunking TV technology: Reflections in drinking glasses

Apart from “enhancement”, another TV myth is this idea of reflections, either in drinking glasses, or heaven forbid peoples eyes (post to follow). Case in point, “Crossing Lines Episode 6 Special Ops – Part 2″. Using a video stream image of a glass half full of water in a remote farmhouse, the team use a reflection in the glass, of a small opening in the window curtain to determine there’s an object on the distant hill which they use to pinpoint the house, after sharpening the image so that the object is crisp. Here’s a representation of the glass.


And here’s what the set-up would look like:


Now the problem here is one of simple optics. The glass in the picture is a multi-faceted glass. The challenge would be having the correct series of angles to reflect the outside image, which we presume is about 90 degrees to the right of the camera.  Below are three photographs taken of my backyard through: (i) a 9-sided glass with water in it, (ii) a round glass with water in it, and (iii) a round glass with no water in it. The 9-sided glass by no means allows views from anything but directly ahead, and the images are compressed horizontally and exist on each facet of the glass. The round glass flips the image horizontally, while also distorting it. This is because light “bends” when it passes though one substance to another of a different density. Light traveled from the air, through the glass, through the water, through the back of the glass, and then back through the air, before hitting the scene on the other side. The round glass with no water in it provides an undistorted un-flipped image which is slightly blurry.


Experiment: Fill a multi-faceted glass with water and put an object to the side of the glass. Rotate the glass around 360 degrees. You will never see the object.  To really see “around a corner” you have to use a prism, or something like the Super Secret Spy Lens from photojojo.

Here is an experiment performed using a window with 2-panes of glass (and an inert gas in between). Opening the window and taking a photograph out the window, with the camera lens placed perpendicular to the window frame result in an image of the side of the house. The image is a reflection, and is doubled due to the 2-pane nature of the window. However it is possible. Not so possible with a multi-paned glass.




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