Pressure

Overview

Pressure is the physical force being exerted on the pen tip.

Key concepts

• The pen senses pressure, not the tablet. The pen communicates the pressure it detects to the tablet.

• The IAF is the smallest amount of pressure an EMR pen will detect and report.

• The Pen pressure range is the range of physical force the pen can sense and output as pressure. In other words, its lower bound is the IAF and its upper bound is the maximum pressure.

• A tablet splits the pressure range into segments called Pen pressure levels.

• The Pen pressure response is the pen hardware's pressure behavior. It describes how a specific pen maps physical pressure to the logical pressure number sent to your computer.

• A Pen pressure curve modifies or processes the pressure response of a pen. You can use it to solve or mitigate some pressure problems, or to achieve certain creative effects.

• A Pressure curve dead zone uses a pressure curve to effectively increase the IAF.

• The vast majority of drawing tablet pens are too sensitive to small changes in physical pressure near the IAF. This creates problems when drawing at low physical pressure. You can address this with Pen pressure curves or pressure smoothing.

• Tilt affects pressure. The pen is more sensitive when it is held perpendicular to the tablet surface.

"Under pressure" video series

If you'd prefer to watch, I built the "Under Pressure" video series on YouTube that goes deep into how pressure works. It explores all these concepts in great detail.

Relationship between the pen and the tablet

• The pressure sensing mechanism is in the pen, not the tablet.

• Tablets do play a role in processing pressure. They

  • Determine the number of pressure levels

  • Translate the pressure information from the pen into those levels

  • May process the pressure data before it is sent to the computer

Units

When dealing with the pressure (i.e. the force applied to the tip), the standard unit used is gram force abbreviated as gf.

You may occasionally see this force described as grams and see the unit g used. This is technically incorrect, since grams are a unit of mass, not force.

Disabling pressure

Sometimes it is useful to disable pen pressure. For options, go here: Disabling pen pressure.

How EMR pens measure pressure

There are two different techniques. The newer one uses a pressure sensor in the pen. More here: EMR pressure detection.

Notes

• Pens, even of the same model, differ a little in their pressure sensitivity.

• Pressure sensors are subject to wear. Over time, a pen may become less sensitive than it used to be. In practice, I have never noticed this in a meaningful way.