Why does the Surface Pro 3 digitizer have only 256 pressure levels?
Now on the redit, the AMA of the Surface development group is passing . One of the questions was why in the third surfer, they used not the Vakomovsky digitizer, but the N-Trig, which offers only 256 pressure levels. People are worried that this will not be enough for confident work with a stylus in drawing.
The answer turned out to be extremely entertaining and intelligible, and therefore I made a free translation. Some things are not interesting and lowered, so do not scold much. At the same time I will say that some terms like touch digitizer, I translated as I could, so if you know a well-established translation, write in a personal.
')
Hi, this is Stevieb. I was expecting a question about the digitizer, and therefore I considered the answer a few days before the AMA. I hope that you and other interested people will find it useful.
At the moment there are three types of pen digitizers: electromagnetic, passive-capacitive (in which the tip of the pen "pretends" with a finger), and active-capacitive.
Electromagnetic based on a receiving printed circuit board usually located under the screen and the backlight. This board is not related to the finger digitizer, which is usually located in front of the screen. On the board there are a bunch of flat coils that emit an electromagnetic field (such as one part of a normal transformer). The second part of the transformer is in the pen. When bringing the pen to the screen, this part falls into the EM field and adds load. This load is distributed over several coils and the position of the pen is interpolated from this data. This field works up to 15 mm above the screen and this makes it possible to implement the hover mechanism. Data from the knob (push level, buttons) is transmitted by modulating the frequency. To obtain the orientation of the pen, a secondary grid of coils and some trigonometry are usually required. Orientation is needed to compensate for mechanical parallax. Of all the technologies, this is the oldest.
Passive capacitive styli simply imitate a finger, and work with a finger digitizer.
Finally, active-capacitive solutions began to emerge in the early 2000s. They also work with a finger digitizer, but the tip of the pen introduces an electrostatic signal which is received by the capacitive lines of the digitizer. Imagine a mini-walkie-talkie that transmits signals to miniature antennas built into the screen. The crosshair of capacitive lines (the place where the vertical and horizontal lines intersect), which receives the strongest signal corresponds to the position of the pen. Of course, for the work of such a pen, it requires batteries. By the way, you might have heard how a couple of years ago we bought a developer of a cool, active capacitive digitizer, Perceptive Pixel. I’m sure this is the best pen technology for large screens. The market for this type of digitizer is actively developed by several manufacturers, because they are well integrated into existing digital digitizers.
Now let's think about what makes the stylus different in terms of iron.
1. Accuracy rules the ball. The more accurate and stable the tip of the pen draws on the screen, the easier and more convenient to use it. The accuracy problem depends on three parameters.
2. Tactile and sound sensations. The pen should feel and sound like you are writing / drawing on real paper.
3. Pen itself - its weight, material, ergonomics.
4. Stable and accurate pressure assessment.
5. Buttons to switch modes.
6. Delay drawing. It strongly depends on the application, and good developers strive to reduce it to a minimum.
7. Blocking the palm to eliminate false touches.
8. Integration with the device.
Now that we know a little about the topic, let's discuss some of the advantages and disadvantages of the above technologies. I will deliberately skip the discussion of passive-capacitance digitizers due to their obvious flaws. Also, I want to say that among these technologies, in a general aspect, there are no obvious leaders. It all depends on the specific implementation, and the integration of a specific digitizer into a specific device. I personally watched the poor implementation of all three technologies by various vendors. So using a type of digitizer alone does not guarantee success.
1. Accuracy. Such styluses can be very accurate, but it strongly depends on the implementation. In order for such a pen to work well along the edges of the screen, the receiving printed circuit board behind the screen must be slightly larger than the screen itself. Also metal objects and magnets near the screen or even near the device are strictly contraindicated, as they introduce distortions that greatly worsen the accuracy. These requirements limit the manufacturer on screen design and materials used. And since the EM fields drift depending on the environment, the vendor needs to calibrate the digitizer well, as well as take into account situations where the user places a metal object in front of the device (for example, a case with a metal insert).
2. Visual parallax - depends on the thickness of the screen, and none of the technologies has a significant advantage in this regard.
3. Electronic parallax - since the receiving board is buried deep in the device, the digitizer must calculate the orientation of the pen and calculate the position from the orientation. The calculation of the position often depends on where the tip of the pen is located on the screen. Therefore, you cannot write a single mathematical transformation for all points on the screen. Rarely does anyone bother with this and usually choose some easier way.
4. Stability and accuracy across the screen. The easiest way to check is to take a ruler and draw several diagonal lines across the screen. Assess the evenness of the lines. Most likely they will not be perfectly even, because it is difficult to achieve.
5. The feather itself - its weight, material, ergonomics. An EM stylus cannot be made of metal. They can be of any size and shape, from thin and uncomfortable (but which can be plugged into the slot in the device), to large and more similar to handles. They also don't need batteries.
6. Stable and accurate pressure assessment. Usually with this EM stylus everything is in order. By the way, it depends more on the pressure curve than on the number of bits to be reportable. I will explain in more detail below.
7. Integration with the device - since the EM digitizer is separated from the finger digitizer, it will need about 0.4-1 mm of thickness, several millimeters around the screen and several tens of grams.
1. Accuracy. In the past, I have seen here (translated: MS must be assumed) not the best implementations, but I am very pleased with what we achieved in Pro 3. We did raise the bar. The pen has become much more accurate and all over the screen. The first thing I hear from artists who work with this pen for the first time is praise for accuracy.
2. Visual Parallax - depends on the thickness of the screen, as I said. In Pro 3, we reduced it to 0.75 mm, and this is one of the lowest numbers I have seen with pen tablets.
3. Electronic parallax - since the capacitive lines are located immediately under the glass (which is only 0.55 mm thick!), The parallax is rather small, and this is one of the reasons why our feathers are felt more precisely.
4. Stability and accuracy across the screen - make a test with a ruler!
5. The feather itself - its weight, material, ergonomics. Since we are not limited to the material, we made a cool pen of adonated aluminum, which lies comfortably in the hand. Yes, she needs a battery, but with a battery, you can emit a more powerful signal, which allows, for example, by pressing the butt to open OneNote from a distance of one and a half meters! This can not be done with a passive pen.
6. Delay - as I said, the delay is highly dependent on the specific application. We really have one problem - a small lag is noticeable in the hover, but it is only in the hover.
7. Integration with the device - in comparison with the EM digitizer, there are practically no limitations. For example, our Type keyboards cling to the surfboard with magnets, which would interfere with the EM field.
Well, as promised, let's talk about the main Fedor, about pressure. Some here worry that the 256 levels of pressure are not enough. You know, you can promise any resolution, 10, 12, 14, 16 bits ... But in the end, even if the system issues a 16-bit number, this does not mean that it contains 16 bits of useful information. It's like in cameras with sensors of 20 megapixels - there is also not always 20 megapixels of useful pictures. You can do an experiment that I did last weekend. I took the best EM tablet I know and compared with Pro 3. First, I downloaded a software called “digiInfo”, which can record Windows messages. I configured it to record pressure messages on both tablets. Then I made a small device that held the stylus and pressed on the screen with a force of about 50 grams (Trans.: Sorry to mix grams with newtons) . I wrote down the reportable statistical pressure, I imported it into an Excel, and I saw what it was: an EM pen with 1024 levels, the standard deviation was three times more than our pen with 256 levels. So, as a result, the performance is the same despite the extra two bits of resolution.
In other words, the Pro 3 pen measures pressure in the range of 10-400 grams and projects to one of 256 levels, and nonlinearly, since human pressure is nonlinear. But about 1-1.8 grams per level is obtained. And EM-pen measures in the range of 10-500 grams and theoretically gets about 0.4 grams per level.
...
from translator:
Then I lost the thread of conversation. Stevie started talking about scales and signal averaging.
But after thoughtful analysis, it seems to me that he suggests taking any exact scales and see how accurately you can exert pressure with your finger. He apparently means that 10-bit pen has excessive accuracy, which leads to excessive noise, a strong signal averaging, and as a result lag.
The answer turned out to be extremely entertaining and intelligible, and therefore I made a free translation. Some things are not interesting and lowered, so do not scold much. At the same time I will say that some terms like touch digitizer, I translated as I could, so if you know a well-established translation, write in a personal.
')
Hi, this is Stevieb. I was expecting a question about the digitizer, and therefore I considered the answer a few days before the AMA. I hope that you and other interested people will find it useful.
At the moment there are three types of pen digitizers: electromagnetic, passive-capacitive (in which the tip of the pen "pretends" with a finger), and active-capacitive.
Electromagnetic based on a receiving printed circuit board usually located under the screen and the backlight. This board is not related to the finger digitizer, which is usually located in front of the screen. On the board there are a bunch of flat coils that emit an electromagnetic field (such as one part of a normal transformer). The second part of the transformer is in the pen. When bringing the pen to the screen, this part falls into the EM field and adds load. This load is distributed over several coils and the position of the pen is interpolated from this data. This field works up to 15 mm above the screen and this makes it possible to implement the hover mechanism. Data from the knob (push level, buttons) is transmitted by modulating the frequency. To obtain the orientation of the pen, a secondary grid of coils and some trigonometry are usually required. Orientation is needed to compensate for mechanical parallax. Of all the technologies, this is the oldest.
Passive capacitive styli simply imitate a finger, and work with a finger digitizer.
Finally, active-capacitive solutions began to emerge in the early 2000s. They also work with a finger digitizer, but the tip of the pen introduces an electrostatic signal which is received by the capacitive lines of the digitizer. Imagine a mini-walkie-talkie that transmits signals to miniature antennas built into the screen. The crosshair of capacitive lines (the place where the vertical and horizontal lines intersect), which receives the strongest signal corresponds to the position of the pen. Of course, for the work of such a pen, it requires batteries. By the way, you might have heard how a couple of years ago we bought a developer of a cool, active capacitive digitizer, Perceptive Pixel. I’m sure this is the best pen technology for large screens. The market for this type of digitizer is actively developed by several manufacturers, because they are well integrated into existing digital digitizers.
Now let's think about what makes the stylus different in terms of iron.
1. Accuracy rules the ball. The more accurate and stable the tip of the pen draws on the screen, the easier and more convenient to use it. The accuracy problem depends on three parameters.
- Visual parallax - from the tip of the pen to ink on the screen. This is where you think the tip of the pen is.
- Electronic parallax - from pen tip to digitizer. This is where the digitizer thinks is the tip of the pen.
- The accuracy of the digitizer and the linearity of the distortion over the entire screen area.
2. Tactile and sound sensations. The pen should feel and sound like you are writing / drawing on real paper.
3. Pen itself - its weight, material, ergonomics.
4. Stable and accurate pressure assessment.
5. Buttons to switch modes.
6. Delay drawing. It strongly depends on the application, and good developers strive to reduce it to a minimum.
7. Blocking the palm to eliminate false touches.
8. Integration with the device.
Now that we know a little about the topic, let's discuss some of the advantages and disadvantages of the above technologies. I will deliberately skip the discussion of passive-capacitance digitizers due to their obvious flaws. Also, I want to say that among these technologies, in a general aspect, there are no obvious leaders. It all depends on the specific implementation, and the integration of a specific digitizer into a specific device. I personally watched the poor implementation of all three technologies by various vendors. So using a type of digitizer alone does not guarantee success.
So, let's start with electromagnetic styluses
1. Accuracy. Such styluses can be very accurate, but it strongly depends on the implementation. In order for such a pen to work well along the edges of the screen, the receiving printed circuit board behind the screen must be slightly larger than the screen itself. Also metal objects and magnets near the screen or even near the device are strictly contraindicated, as they introduce distortions that greatly worsen the accuracy. These requirements limit the manufacturer on screen design and materials used. And since the EM fields drift depending on the environment, the vendor needs to calibrate the digitizer well, as well as take into account situations where the user places a metal object in front of the device (for example, a case with a metal insert).
2. Visual parallax - depends on the thickness of the screen, and none of the technologies has a significant advantage in this regard.
3. Electronic parallax - since the receiving board is buried deep in the device, the digitizer must calculate the orientation of the pen and calculate the position from the orientation. The calculation of the position often depends on where the tip of the pen is located on the screen. Therefore, you cannot write a single mathematical transformation for all points on the screen. Rarely does anyone bother with this and usually choose some easier way.
4. Stability and accuracy across the screen. The easiest way to check is to take a ruler and draw several diagonal lines across the screen. Assess the evenness of the lines. Most likely they will not be perfectly even, because it is difficult to achieve.
5. The feather itself - its weight, material, ergonomics. An EM stylus cannot be made of metal. They can be of any size and shape, from thin and uncomfortable (but which can be plugged into the slot in the device), to large and more similar to handles. They also don't need batteries.
6. Stable and accurate pressure assessment. Usually with this EM stylus everything is in order. By the way, it depends more on the pressure curve than on the number of bits to be reportable. I will explain in more detail below.
7. Integration with the device - since the EM digitizer is separated from the finger digitizer, it will need about 0.4-1 mm of thickness, several millimeters around the screen and several tens of grams.
Active-capacitive stylus
1. Accuracy. In the past, I have seen here (translated: MS must be assumed) not the best implementations, but I am very pleased with what we achieved in Pro 3. We did raise the bar. The pen has become much more accurate and all over the screen. The first thing I hear from artists who work with this pen for the first time is praise for accuracy.
2. Visual Parallax - depends on the thickness of the screen, as I said. In Pro 3, we reduced it to 0.75 mm, and this is one of the lowest numbers I have seen with pen tablets.
3. Electronic parallax - since the capacitive lines are located immediately under the glass (which is only 0.55 mm thick!), The parallax is rather small, and this is one of the reasons why our feathers are felt more precisely.
4. Stability and accuracy across the screen - make a test with a ruler!
5. The feather itself - its weight, material, ergonomics. Since we are not limited to the material, we made a cool pen of adonated aluminum, which lies comfortably in the hand. Yes, she needs a battery, but with a battery, you can emit a more powerful signal, which allows, for example, by pressing the butt to open OneNote from a distance of one and a half meters! This can not be done with a passive pen.
6. Delay - as I said, the delay is highly dependent on the specific application. We really have one problem - a small lag is noticeable in the hover, but it is only in the hover.
7. Integration with the device - in comparison with the EM digitizer, there are practically no limitations. For example, our Type keyboards cling to the surfboard with magnets, which would interfere with the EM field.
Well, as promised, let's talk about the main Fedor, about pressure. Some here worry that the 256 levels of pressure are not enough. You know, you can promise any resolution, 10, 12, 14, 16 bits ... But in the end, even if the system issues a 16-bit number, this does not mean that it contains 16 bits of useful information. It's like in cameras with sensors of 20 megapixels - there is also not always 20 megapixels of useful pictures. You can do an experiment that I did last weekend. I took the best EM tablet I know and compared with Pro 3. First, I downloaded a software called “digiInfo”, which can record Windows messages. I configured it to record pressure messages on both tablets. Then I made a small device that held the stylus and pressed on the screen with a force of about 50 grams (Trans.: Sorry to mix grams with newtons) . I wrote down the reportable statistical pressure, I imported it into an Excel, and I saw what it was: an EM pen with 1024 levels, the standard deviation was three times more than our pen with 256 levels. So, as a result, the performance is the same despite the extra two bits of resolution.
In other words, the Pro 3 pen measures pressure in the range of 10-400 grams and projects to one of 256 levels, and nonlinearly, since human pressure is nonlinear. But about 1-1.8 grams per level is obtained. And EM-pen measures in the range of 10-500 grams and theoretically gets about 0.4 grams per level.
...
from translator:
Then I lost the thread of conversation. Stevie started talking about scales and signal averaging.
I think it can be .1 increments…. This is not the case. It adds up to the stylus ...
But after thoughtful analysis, it seems to me that he suggests taking any exact scales and see how accurately you can exert pressure with your finger. He apparently means that 10-bit pen has excessive accuracy, which leads to excessive noise, a strong signal averaging, and as a result lag.
Source: https://habr.com/ru/post/224365/
All Articles