Pressure levels, pressure curves, and human performance
Hi, we've been talking about pens' pressure levels and pressure curves and how many levels are enough, and a while ago I decided to test this stuff empirically, though with a sample size of one, myself.
What the pen suppliers say:
- Decades-old Wacom pens advertised having 10 gram-force minimum and 300 gf maximum. Later pens advertised 3 gf and eventually 1 gf. Pressure levels started off at 256, hovered many years at 1024, and in recent years ballooned up to 8192.
- N-trig, and subsequently Microsoft, advertised 10 gf minimum and 300 gf maximum. Advertised 256 then 512 levels of pressure, and recently 4096.
- I used a 500 gram scale that's supposedly accurate to 10 milligram. It's a cheap Chinese scale with no certification and I do not own any certified 10 milligram (or even 100 mg or 1 g) weights, so I cannot verify this. However, testing various non-certified weights from 10 to 500 g, they were all accurate to within 20 mg, which should be good enough for my purposes (see results).
- I rested my arm on a desk, held the pen in my hand naturally (dynamic tripod), and placed the tip of the pen as lightly as possible on the scale, then attempted to increment the force as carefully as I could. I did this with two Wacom EMR pens (Bamboo Feel and Fujitsu toothpick pen) and a Wacom AES pen (Bamboo Smart), but results were largely the same across all pens.
- Attempting the lightest touch without moving, the reading fluctuated from 1 to 4 grams
- When moving the pen tip along the scale with the lightest touch, the reading fluctuated from 2 to 11 grams
- Lightly writing my name on the scale, the reading fluctuated between 20 and 60 gf, with 30 gf being the most frequent reading
- Writing normally was about 60 gf
- Pushing 400+ gf was uncomfortable.
- LEVELS: I could, barely, control the reading in 5 gf increments, but even though I managed to "center" around a desired reading (15, 20, 25... 195, 200, 205... 295, 300) there was a lot of fluctuation of about ±10 gf. When moving the pen, there was even more fluctuation. There was no range where I could discernibly exert more accurate control, so my personal pressure curve is completely linear in this range.
- 256 pressure levels (actually force levels) between 1 and 300 gram-force is fine, as long as you put most of the levels on the lower range of the pressure curve for those who are able to control their hand in 1 gf increments.
- I don't think it's humanly possible to control 1-300 gf in 8192 increments (~35 mgf increments!) as I had trouble even attempting 5 gf increments. Current pressure level numbers are overkill of two orders of magnitude.
TL;DR: having over 1000 levels spread between 1 and 300 gram-force is overkill, having 8000 pressure levels is overkill by orders of magnitude. It's all marketing hype.
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