The Picture Of a Screen on your Camera
You look around, only to find science everywhere
There have been a gazillion times I have needed to snap off a web page. Generally, while working on a project on my laptop to share it with my mates, rather than committing the arduous task of sharing the link.
The (specimen) images, when shot on my Redmi Note 3, look like those shown ahead ;


What are these lines?
This an interference or say, a geometrical design that results when a set of straight or curved lines are superimposed. Famously known as the Moiré pattern, it is extensively applied in mathematics, physics and art.


But how does it creep into our photos?
The mechanism of capturing a scene by a digital camera, consists of a grid of pixels on the imaging element (the screen), while the LED display has a coloured grid of pixels. They don’t line up exactly, hence the odd patterns.
Had the superimposition between the set of fine lines been absolutely perfect, one could never have seen interference.
Okay, so what about Moiré patterns while taping CRT (Cathode Ray Tube) Displays?
Aha! They look even more significant, since LED displays reduced the interference.
A Cathode Ray Tube shoots electrons onto the screen at the frequency of 60Hz-120Hz, which means 60–120 times a second, creating an image on the screen. If you try taping it using a camcorder, you will get a flickering black line pattern, same as in the image shown above of straight line Moiré pattern.
How do we eliminate this?
According to Nikon,
In order to reduce (or eliminate) moiré, a special anti-aliasing filter is mounted in the camera. If too strong a filter is mounted an overall soft image will be produced, but with no moiré. If a weaker filter is chosen the image will be sharper, but there is more of a chance for moiré to happen in some circumstances. Nikon has chosen to produce the sharpest image that can be made, even though there may be some moiré in parts of some images.

Information Sources:
Encyclopedia Britannica, Wikipedia, Physics Stackexchange, Nikon Global
