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Process

Pressure range data

I am actively collecting pressure range data.

All the data is stored here: https://1drv.ms/x/s!Aml8i4Jd6crCkTerfXD_1zsIxg3A?e=7HqT7T

Key notes:

  • I am not good at measuring IAF, so I believe my measurements show higher IAF than is accurate

  • I am confident in my max pressure measurments

  • I assign inventory IDs to my pens so that I can track them over time

  • Remember a given model of pen has individual units that can have widely vartying IAF and MAX pressure values.

Measuring hover

Overview

To more accurately assess hover height, I use a small "staircase" that cost up by 0.5mm increments to test how hover works with tablets.

The hover testing tool

Testing process

  • Overall I move "down to up"

  • I begin with the pen placed on the first step which represents 0.5mm from the tablet surface.

  • I then move up each step (0.5mm increment each time)

  • On each step I notice

    • Whether the tablet detects the pen

    • If the tablet detects the pen, then whether there is any hover jitter. And how much hover jitter there is.

  • I move up the steps until the pen is no longer detected by the tablet.

3D printing notes for tool

Printing details

  • Printer: Bambu X1C

  • Nozzle: Bambu Lab X1 Carbon 0.4 nozzle

  • Filament: Bambu Basic PLA

  • Layer height: 0.2mm

  • Initial layer height: 0.2mm

  • Plate: Textured PEI Plate

Accuracy

Because the layer height is 0.2mm:

  • The whole number steps are very accurate

  • The intermediate steps such as 1.5mm, 2.5mm are slightly thicker than they should be.

I measured the steps with a digital caliper and had these results:

  • 1.0mm step = 1.04mm

  • 1.5mm step = 1.63mm

  • 2.0mm step = 2.04mm

  • 2.5mm step = 2.63mm

  • 5.0mm step = 5.04mm

  • 5.5mm step = 5.65mm

  • 10.0mm step = 10.04mm

  • 10.5mm step = 10.64mm

Measuring pressure

Scale

I use this scale US Solid Scale (model number USS-DBS86-5).

It is delicate enough to measure 0.1g which makes it good for IAF testing and can support 5kg of weight which is good for handling the weight of smaller pen displays.

Connecting the scale to a computer

Cable

This specific cable works to connect the serial port on the scale to a USB port on the PC

CableCreation USB to RS232 Adapter with PL2303 Chipset (amazon link)

Programmatically getting the pressure data to a PC

Tablet expert Kuuube, has provided some sample code to read the data from the scale into a PC using Python. See the github project here: us_solid_scale_reader

Measuring display sharpness

Overview

Pen displays have some anti-glare treatment that introduces a small amount of blur. It can vary widely between pen displays. I've created a simple test image to so I can consistently evaluate the blur.

Test image

It's a small PNG file with black and white pixels.

There are 8 samples.

Process

  • Open the image in Krita

  • Set the zoom to 100% so that every pixel in the image corresponds to exactly 1 pixel on the display.

Measuring report rate

Overview

For report rate testing, several tools can be used.

Local client tools

OpenTabletDriver

In OTD's tablet debugger the report rate is shown.

Osu!

In osu, go to settings, ten turn on raw input. There is a counter next to it for report rate. (this was a tip from Kuuube)

Web-based tools

You have to keep the hovering and pen moving to get the max report rate since these tools only report a change when the pointer has moved.

Notes

  • For a given tablet, you may get different report rates when used wired and wirelessly

  • For a given tablet, you may get different report rates with different pen models

Measuring diagonal wobble

I measure diagonal wobble using a simple procedure

Resources

Diagonal template image - a standard PNG file created with using Adobe Illustrator. This provides visual guides that make it easier for the testing. Image is shown later in this doc.

Ruler - I use a simple plastic ruler. I do not use metal rulers because they might interfere with the EMR tech in the pen.

Driver - I use the latest manufacturer driver. For very old tablets that don't have recent drivers, I use OpenTabletDriver.

Application - Krita

Testing process

  • Verify the plastic ruler has no rough spots or bumps that would affect the measurement. It should be smooth.

  • Tablet configuration

    • For pen tablets, set the active area to a single display.

    • For pen tablets, set the driver to match the aspect ratio of the tablet to the display.

  • App configruation

    • Load the diagonal template image

    • Set Krita zoom to 100%.

    • Set Brush to Ink-2 Fineliner with default brush settings and set size to 5 pixels.

  • Drawing

    • The template requires 3 sets of lines drawn at different speeds - 3 lines for each speed

    • Draw the line from the lower left to the upper right.

      • Follow the specified speed as much as possible

      • pen tilt = about 30 to 40 degrees from vertical.

  • Save as a PNG

Evaluation wobble (DRAFT)

Considerations

  • MAGNITUDE - how wobble is physical displaced from "center" of line.

  • VELOCITY - Is wobble visible in slow, medium, fast strokes

Scale

  • VERY LOW - Strokes easily confused for a perfectly straight line

  • LOW - lines mostly straight with occasional and minor wobble

  • MEDIUM - moderate Wobble visible in majority of lines

  • HIGH - moderate wobble available in lots of lines

  • VERR HIGH - lots of wobbling in lines

Wobble testing template image

Diagonal wobble samples

Once you have learned about diagonal wobble , you may want to see how much of it specific tablets have.

You can find my collection of diagonal wobble samples here: https://1drv.ms/f/s!Aml8i4Jd6crChTjTXo89k5jO8mb8?e=Y1NOlX

They are organized by brand

More info: Measuring diagonal wobble.

Perfect pressure sensitive lines

It's not possible for a human to push down on the tib of the pen with a perfect monotonically changing amount of pressure.

To do this I use a Kuuube's pressure emulation plugin for OpenTabletDriver.

You can download the plugin from here: https://github.com/Kuuuube/Pressure_Emulation

This is my standard configuration

Pressure Resolution - to simulate N levels of pressure. Shown below is 256. Setting it to zero will not affect the pressure values

Line length - 800

Line X Offset - 200

Tablet evaluation

These are my notes on the things to look at when I evaluate a tablet. This is a work in progress and evolves over time.

Summary

These are the quick summary highlights.

  • Model number

  • Active Area - dimensions and diagonal size

  • Release year

  • Key interesting points

  • Links

    • Any manufacturer videos

    • Product page

    • User manual

Display > basics

  • Display size - should be same as active area

  • Display resolution

  • Aspect ratio

  • Response time

  • Max refresh rate

  • Brightness

    • Future: see if this can be independently measured

  • Contrast ratio

  • Display panel tech: IPS, OLED, etc.

  • Bit depth

    • If >8pp clarify if it is using FRC or not

  • Anti-glare treatment: Etched glass vs AG film

  • Laminated?

Pen

  • Pen model ID that comes with tablet

  • What is default nib in pen

Pen Pressure

  • Manufacturer stated IAF and max pressure

  • Measure IAF

    • I am not good at IAF - so for now leave this out

  • Measure Max Pressure

  • Pressure transition at low pressure

    • Look for instability / pulsing

Pen tracking accuracy

  • Accuracy in middle versus corner and edges

  • Tilt compensation

Diagonal Wobble

Pointer lag

  • How does it compare to other tablets?

Pen Tilt

  • Does tilt work correctly at edges and corners?

Pen Hover Height

Pen Hover -> Drag transition

Background: Some tablets use one smoothing algorithm on hover and a different one on drag (when the pen is pressing down) and so the transition between these smoothing algorithms can create a slight jump in pointer position as the pen hits the surface.

Check for any hover-drag transitions that cause pointer movements.

Display > Parallax

Anti-glare sparkle

Display > Color modes

  • List color modes

  • Identify which color modes the testing was done under

Display > other

  • Pixelation:

  • Dead pixels - did you notice any?

  • Backlight bleed - take photo in a darkened room

  • Display sharpness

    • Are the pixels clear when viewed close up?

    • How blurry is it compared to other pen displays?

OSD

  • How do you launch the OSD?

  • Does the OSD respond to touch even if touch is off on the tablet?

  • Take photos of the OSD screens

Ports

  • List all the ports

Connections and cablings

  • How was the tablet connected to your computer and power

  • Does it support single USB-cable connection

  • Is the USB-C port recessed?

Express Keys

  • Does it come with any express keys, dials, etc?

VESA mounting

  • Does the tablet support VESA mounting.

  • If so, which size is used

  • If you used it with an monitor arm, identify the arm

Stand

  • Does it come with a stand?

  • If so,

    • Identify model number of stand

    • Does the stand use VESA mounting?

    • How much wobble does the stand have

    • Does the stand support height adjustment

    • Does the stand support tilt adjustment

Surface texture

  • How does it feel compared to other tablets?

  • Try with plastic and with felt nib

Legs

  • Does the tablet have legs?

  • If so, what angle do the legs place the tablet at?

Fans

  • Does the tablet have fans?

Ergonomics

Heat

  • At 50% brightness for an hour - how hot does it feel to the touch?

  • At 100% brightness for an hour - how hot does it feel to the touch?

  • Are there any noticable hotspots?

Fan Noise

  • What is the noise experience at 50% brightness?

  • What is the noise experience at 100% brightness?

Touch

  • Is touch supported? On Windows? On MacOS?

Other

Sound support

  • Does it have a headphone jack?

  • Does it have speakers?

Can you use the tablet as a pen display?

  • If so how would you do that?

Microscope

Overview

Occasionally I use this microscope to get close-up pictures of nibs, and sometimes LCD panels.

Basics

Notes

  • The microscope behaves just a like a webcam. You can use your computer's built in camera to see the image it produces.

  • Optionally, you can install the Plugable Digital Viewer App which provides some additional features.

Measuring PWM Flicker

Overview

This doc describes how I test for PWM flicker in a display. To learn more about what PWM flicker is go here: PWM flicker.

Process for measuring

  • Get a smartphone

  • Set the photo mode to "pro"

  • Set shutter speed to the fastest possible. For example 1/12000s

  • Point the smartphone camera at a display to test for PWM flicker

  • Set the display brightness to the lowest setting (0%)

  • Now steadily increase the display brightness from 0% to max brightness (100%) and look at the phone's camera preview

  • If there is PWM flicker

    • you will see it as horizontal black bars that move up and down the display

    • The black bars will be thicker when the brightness is lower