Recently at drawboard we’ve started using the Surface Pen Slim 2 in-house.

Drawboard supports the Surface Pen Slim 2 with Haptic feedback to provide the user with the feeling of friction as they ink in the Drawboard PDF windows application.

In fact, Drawboard responds to all functionality with the pen, including changing of the pressure sensitivity, strength of the haptic feedback when inking, as well as being able to pick up on use of the back of the pen for erase, and the pen’s buttons can also be configured to launch Drawboard PDF.

At Drawboard PDF we pride ourselves on the digital inking experience we provide users.

There are 3 main aspects to make digital ink feel like the real thing:

1. Pressure sensitive ink

a.) With pressure sensitivity there’s first the question of “is it pressure sensitive” a binary answer based on whether the pressure of the pen or finger is picked up by both the software and hardware to produce a different width of ink. Drawboard is certainly pressure sensitive.

b.) The second part of this is just how sensitive to pressure the application allows for. Some applications when you test their pressure sensitivity will only allow for 3 or 4 ink widths depending on pressure. Microsoft states that their new Slim Pen 2 will pick up on over 4000 different pressure levels, which sounds like a great deal, however it’s up to the software to interpret each level and assign it a width somewhere on the spectrum allowable for that pen point size. Drawboard PDF offers over 30 different widths, with smooth transitions between them.

c.) Lastly you have the ratio of max width (at max pressure) to minimum width. For drawboard PDF this number is around 4:1

2. Digital Ink Latency

Latency is an important factor in creating the feeling of real ink. When you ink with a physical pen or pencil the latency is zero. That is when the pen is there, and still in contact with the page then so too is the ink. In the digital world this is obviously much more complicated. Many things can affect latency, but the first fact will be a theoretical maximum that the hardware you’re using can achieve, this is based on the number of samples collected at the pen tip, the rate the pen converts them into bluetooth signal, then the hardware must receive it and process it into data the application can understand, process, and display on the screen.

The easier way to consider this is: how far behind does the ink fall when stroking quickly?

At an observable level, when I’m moving my hand at approximately (very approx) 1 meter per second. By recording the screen activity on a high speed video (8x) slowed down I can determine the furthest lag behind is about 2cm. Therefore 0.02/1= 20ms. This is larger than the theoretical minimum for the slim pen 2 of 12ms. But that’s to be expected as any software/application whether it be 3rd party or 1st must interpret the landed signal into pixels on the page.

When inking text/script in drawboard PDF latency is not noticable. Any latency can only be observed when moving your stylus very quickly across the screen in large strokes.  

3. Stylus to Screen Friction

For a long time this one has been largely unanswered in the market for digital inking. Many hardware solutions have experimented with different pen tip types which grip the screen to different extents, as well as screen coverings and treatments to make this feel more real.

Microsoft’s latest solution for this is to provide haptic feedback, in the form of very fine/small haptic vibrations produced by the pen when the pen is in contact with the screen and moving.

To Microsoft's credit the haptic feedback on the Surface Pen Slim 2 (at 100%) is as subtle as real penned ink on a page of standard paper. That is it’s only just noticeable. Or put another way, the user no longer “notices” that there is no friction, and therefore an unnatural writing experience.

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