Originally Posted by
brennanyama
In it's purest form, a digitizer is any device that digitally represents some kind of input, meaning that your mouse, keyboard, even camera are all types of digitizers; however, the term only recently surfaced in the technology world with the upbringing of touch screen devices. So generally, when someone says "digitizer", they are referring to some kind of touch screen, or touch pad device. When we refer to "active" and "passive" digitizers, we are further targeting a certain type of touch screen.
A passive digitizer is the most common type of touch screen device, which requires the input to physically touch the screen in order to receive input. These types of passive touch screens come in two major types; capacitive and resistive. Resistive touch screens work by sensing where pressure is applied to the surface of the screen, which is flexible, and depresses upon physical contact. Resistive touch screens are considered older technology, and are generally found on older touch screen devices, although there are still many new devices which utilize a resistive screen. Capacitive touch screens work by generating a small electric field on the screen, which is disrupted when the user touches the screen with their finger. The device then "approximates" the geographical center of the disruption, and uses this as the exact point of the input. Capacitive touch screens are newer technology, and can be found on the iPhone, and nearly all of the new touch screen devices (the adam most likely amongst them). Although capacitive touch screens are considered to be superior to resistive ones, both types have their pros and cons. Resistive touch screens are far more accurate than capacitive screens because they can be interacted with a stylus, or anything with a fine point, and because they sense a physical depression rather than a disruption of an electric field, they are more more reliable in terms of accuracy. However, resistive touch screens do not support multiple touch input points, and because of their mechanism, they block out a lot of the visual screen below it, resulting in less clarity. Capacitive screens are much more responsive than resistive ones (less pressure needs to be applied), supports input from multiple touch points, and block out much less of the screens clarity than resistive screens. However, they come with the general gripe of being "inaccurate" because they work by approximating the geographic center of a touch input. This problem is somewhat solved by using special "capacitive styluses", but these come with mixed results; capacitive screens still are forced to approximate a geographical center with a far from reliable detection system (the electric field), making very inferior to resistive touch screens in terms of accuracy.
An active digitizer is a powered digitizer, which requires a specialized input device, such as a stylus or pen. (NOTE: Do NOT confuse the stylus of an active digitizer with the stylus of a resistive touch screen. An active digitizer MUST use the stylus it comes with, while a resistive touch screen stylus is just a piece of plastic, you can use anything for input). The advantage of an active digitizer is that it can tell when the tip of the input "pen" is in the near proximity of the touch screen. This means that you can "hover" the pen over the surface of the touch screen, and the computer would be able to follow the pen with a cursor, even though the pen is not physically touching the screen. How exactly this works, even I don't know (ask a professional). An active digitizer has the added advantage of being significantly more accurate than using a capacitive stylus with a passive capacitive touch screen; however, it also has it's disadvantages. An active digitizer is bulky (takes up more physical room on top of the actual LCD screen), it kills the battery faster, but most of all, it's significantly more expensive.
Most active digitizers on the market are dual capacitive/active digitizer touch screens. This means that they are able to accept input from your finger (just as a passive capacitive screen would), as well as accurate input from the included pen. This is another iteration of the term "multitouch", or the ability to accept multiple types of touch input (not to be confused with multiouch, the ability to detect multiple points of input on the screen).
), for the same price as the price increase would be for having an active digitizer
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I don't know if you've experienced handwriting recognition on any other device than the one you mentioned, but assuming you are only referring to that device, I wonder if it was installed with a poor implementation of it. Personally, I loved the hadnwriting on my older Palm IIIxe, iPaq hx2495, and my HTC Tilt. I first learned the notations on my Palm and was able to carry that over to every device I used since. I used each device frequently to jot quick notes during a meeting or something and can't recall a time that I dreaded it. I never noticed lags. I admit there were a few rare times it transcribed a letter I didn't intend for it to, but I can probably count on both hands how many times that happened over an 11 year period. I realize these devices had different screen technology and I can't arugue one way or the other on the price issue, but given that I could probably write 10 times faster on pulp, I personally think I would write on a tablet (legibly) 5 times faster than trying to type notes on a keyboard. I'm a pretty decent typist, but I cannot fathom trying to keep up with a lecture using a keyboard at all (not to mention all the students mad at me if I didn't have a very quiet keyboard 
). I can see this feature being extremely useful to students in the engineering/math/sciences or music programs...note taking combined with free-hand drawing...engineers dream, lol.
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