by Vincenzo
Drawing tablets, also known as digitizing tablets or graphic pads,
are computer input devices that allows to hand-draw images and graphics in a way that is very similar to drawing on a piece of paper with a pencil or a pen.
Drawing tablets are basically a flat surface upon which the user may "draw" an image using a stylus, a pen-like drawing apparatus. |
Usually, the image is directly displayed on the computer monitor instead of appearing on the tablet itself;
this makes it awkward to use a drawing tablet at the beginning but this is just a feeling and it's very easy to overcome it after a few sessions of practice.
Some of the more expensive tablets however, come as a functioning secondary computer screen that you can interact with directly using the stylus.
In this case the secondary screen works as a virtual piece of paper and you can actually draw on it. This is the closest you can can get nowadays to real drawing using drawing tablets.

Even if there are many different types of drawing tablets, all of them have to accomplish one basic but not easy task: a faithful reproduction of your stylus-holding hand motion into the digital realm.
In order to accomplish this all of the tablets must achieve an effective interaction between the stylus and the tablet and a smooth flow of information between the graphic tablet and the computer/drawing software you happen to be using.
This problem hasn't a unic solution and different companies have tackled and solved it in different ways. It is possible to categorize different tablets according to different mechanisms used to translate the human motion of the drawing hand into digital images.
Passive tablets, most notably those by Wacom, make use of electromagnetic induction technology, where the horizontal and vertical wires of the tablet operate as both transmitting and receiving coils.
The tablet generates an electromagnetic signal, which is received by a circuit in the stylus. The stylus in this case works as an antenna that receives the signal and generates another electromagnetic field that "talks" back to the tablet. You can imagine a two voices dialogue in which the stylus and the tablet alternatively talk to each other like this:
tablet: where are you stylus?
Stylus: I am here!
tablet: where are you stylus now?
Stylus: I am here now!
..
and so forth.
By using electromagnetic signals, the tablet is able to sense the stylus position without the stylus having to even touch the surface, and powering the pen with this signal means that devices used with the tablet never need batteries.
Now, this is an incredible advantage over the competitors. Not having batteries inside, the Wacom stylus are ultra light and ultra ergonomic to use.
Due to this advantage drawing with wacom feels more natural.

Active drawing tablets differ from the passive ones in that the stylus used contains batteries that allow the stylus to generate and transmit a constant signal to the tablet.
As I said earlier this choice has its main disadvantage in having a heavier and bulkier stylus. Batteries need also to be recharged even if these kind of devices use very little energy to work.
But there are advantages to this choice. Eliminating the need to power the pen through he tablet means that such tablets may listen for pen signals constantly, as they do not have to alternate between transmit and receive modes. A dialog between stylus and tablet in this type of graphic tablets sounds like:
Stylus: I'm here, I am here, I am here, I am here...
tablets:...
This could result in less jitter. However I have to point put that with modern computers and excellent integrated drawing softwares jitter with a passive tablets is rarely observed.
Early models were described as spark tablets -- a small sound generator was mounted in the stylus, and the acoustic signal picked up by two microphones placed near the writing surface. Some modern designs are able to read positions in three dimensions.
have also been designed to use an electrostatic or capacitative signal.
For all these technologies, the tablet can use the received signal to also determine the distance of the stylus from the surface of the tablet, the tilt (angle from vertical) of the stylus, and other information in addition to the horizontal and vertical positions.
This allows for an incredible degree of control on the stylus or, to say better, on the quality of your digital marking.
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