Smooth ink on the iPad


To try to understand the software limitations of inking on the iPad, I had earlier described an ad hoc writing experiment I had conducted on some free iPad applications designed for drawing. The goal was to understand whether the software imposed any fundamental limitations on marking on an iPad using a finger or a stylus. Because the device is designed to be operated with a finger, there seem to be some hardware-based limitations on the size of the tip of the stylus that prevent the kind of fine-grained visual feedback one needs to write. My conclusion at the time was that there was something wrong with the way applications got stroke data from the device that made all of them track so poorly.

It appears that I was over-generalizing. First, given the capabilities of the iPad platform to download and render video,  it seems unlikely that the hardware is not capable of providing events fast enough; the question was really about the software. A reader of this blog pointed out that I had missed the Penultimate app, and this app was apparently quite good at handling ink. I had indeed not tested it because at the time I was testing only free apps.

I did, however, try Penultimate, and agree that it does a great job producing smooth ink. It was particularly nice with a Pogo Sketch stylus, producing a nice solid line that responded well to quick movements. There were no jaggies or apparent lag in tracking. This app seems quite good for drawing and sketching.

My goal in evaluating the programs, however, is to figure out how well the iPad supports inking for annotating documents. While some of the mechanics are similar, annotating documents adds a few constraints. The biggest of these, in my opinion, is the ability to create fine lines, to write in a small space. Document margins on reading devices are even smaller than those on paper, and every square centimeter counts.

The problem with Penultimate’s ink is that even at its thinnest setting, it’s too thick. It’s sort of like writing with a sharpie — good for the whiteboard, not so good for paper.

But overall, this app provides yet another brick for the edifice of annotating documents in support of active reading. My sense is that a successful application will need to handle documents like iAnnotate, and inking like a combination of Penultimate and Dan Bricklin’s note-taking app. Even with iAnnotate, inking quality increases tremendously when you write at a high zoom factor for the document, and then shrink it back to a reasonable viewing size. A tool that combines these interactions with the least amount of irrelevant interaction will likely meet the basic requirements for annotating on a device.

The next set of functions that will need to be added involve manipulating documents based on the presence of annotations.

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  1. It seems like the people from Ten One Design are working on improving their stylus+software combination to allow thinner lines, and also incorporate palm rejection.

    Unfortunately they seem to use private APIs to do so, so the improvements will hang on Apple’s good will.


  2. I should have mentioned that the Penultimate app also does a decent job of wrist/palm rejection, although it does leave some (easily erasable) small marks. Not bad overall.

    What is the status of Apple’s private APIs? Doesn’t sound like consistent with their overall approach to controlling every aspect of interaction.

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