I understand this is dated somewhat but I think it is important to add to this.
First off, Mr. Me... You are DEAD WRONG. Pixel Resolution is totally irrelevant. Right down to the basic fact that you don't have a clue about how capacitance touch screen works. It comes from the development of capacitance 'touch sensors'.
First off, iPad touch screen isn't much different than the iPhone and iPod touch. It certainly something that may vary slightly from model to model but bottom line:
This would help a little bit to bring it to laymen terms:
This is founded on touchscreen technology dating back to the 1970s.
Now, the touch screen resolution is probably about the same lines and columns per inch. It is important to note that Wacom uses a different type of technology then the iPad/iPod. The capacitance touch screen technology kind of measures the capacitance of several transparent "touch buttons" aka 'electrodes' at each intersection of the horizontal and vertical lines of transparent conductive compound/ink or whatever. Since the human finger is essentially touching a bunch of these 'touch button' / 'electrode intersection' or electrodes (at times) at any given time. In this message, I may say 'electrodes' but do mean particularly the electrode intersection. Keep in mind that. I am referring to the X & Y intersection of the columns/rows lines. It can calculate your relative pixel location through a math equation / algorithm that computes the center point of your finger from the center of the capacitance 'bubble' based on the values from each of the electrodes where your finger effects the capacitance of the field. There is usually about a 1" bubble that your finger presses. Then it calculates the center because closer to the center point of your finger's contact point, the higher the capacitance and that location usually but not always.
I suspect that the resolution of the touch sensor is probably closer to 5 to 10 lines or columns per inch in the 1st gen iPad. A far cry from say.... 132ppi on iPad or the 5080 lines per inch of Wacom intuos. Due to the analog nature of the capacitance field, I could very well through read values read from each 'electrode' point (after it runs through analog to digital conversion), I could still plot a 'center-point' to relative pixel location(s) that are in between the lines and columns. This gives you the illusion of a touch resolution equal to that of the display resolution. Even though it is not technically so.
Keep in mind also that is it not unusual to be zooming in with various graphic art programs and just about any program on the iPad. Just because you can pixel edit on an iPad via "ZOOMING" which is no different than doing the same thing on a Commodore 64. Even though I could edit per pixel without zoom on a C64 but sometimes zoom made it easier to see the pixel by using a 64x zoom (using an 8x8 character cell to represent one pixel). The iPad graphic software by zooming in is doing essentially the same thing.... using several actual pixels of the screen display to represent a pixel of the digital bitmap/image. The touch layer of the display screen is not the resolution as the LCD display itself.
On the third page of this pdf (pg. 18):
It tells you the original iPod touch resolution. The original iPad would be about the same. I suspect that newer models may have some improvement in that. I doubt anything quite like 100+ columns or rows per inch touch resolution.
Edited by RickAstoria - 10/13/13 at 1:32pm