Amar Sagoo

22 January 2014

Demystifying colour management

Colour management is a pretty arcane subject to most people, even if it's relevant to their work. I recently spent a few days trying to understand it, and encountered two challenges. First, I didn't find any really clear explanation of the concepts involved. Some are thorough but difficult to follow. Others give practical advice without elucidating the fundamentals. The second problem is that there's conflicting advice about best practices when designing for the web.

I’d like to take on the challenge of addressing both of these issues. I will first explain some of the basic concepts behind colour management, using illustrations that hopefully make it easier to understand. I will then talk about practical implications for web-oriented design.

How it works

Colours can be described in different ways, for example as a mix of red, green and blue light, or in terms of their hue, saturation and lightness. In each of these colour models, you can think of the dimensions as forming a "space". One such colour space is called CIE xyY, and I'll use it for my illustrations here. It contains all the colours visible to the average human eye, and has the convenient property that, although it's three-dimensional, you can look at it "from above" and get a nice, two-dimensional map of chromaticities at maximum brightness:

CIE xyY chromaticity diagram

When you're working on a particular display, it'll only be able to show a subset of all visible colours. This range is called its gamut and will have a triangular footprint in the CIE xyY space (as will any other RGB space):

Display space within the xyY space

If our display's colour profile is perfectly calibrated, this means that this sub-space defined by it corresponds exactly to the range of colours we can really see on the display.

11 January 2014

5 years later…

Wow, that was longer between posts than I had intended.

Seriously, though, I'm sorry for the long silence, and for the lack of updates to my software. I'm going to tell you a bit about what's happening with my apps, my life and this blog.

So what’s been going on?

After many years of working mainly as a software engineer with a passion for design, I managed to fulfil my dream of becoming a full-time interaction designer in 2011 by joining Google. I moved from London to Switzerland to join their office in Zurich, where I live today.

Previously, my creative energy needed an outlet outside my job, which my free Mac and iOS apps provided. Since becoming a full-time designer, I feel that much less of my capacity has been available to put into extra-curricular projects.

Let me tell you my plan for each of my apps. There is a general theme of retirement, but I think these are the right decisions to make, and, as I explain at the end, I intend to direct my energy into efforts that I hope will be of more benefit.

10 December 2008


I never used to be particularly interested in designing mobile applications. I just thought it was a hopeless platform, plagued by tiny screens and keys that were designed for inputting numbers (how often do you actually type numbers into your phone?) I also had never thought of my phone as something that I want to use for various applications. This scepticism had become so ingrained that I initially didn't even see much point in Apple opening up the iPhone for third-party developers. I thought it might destroy the purity of this well-designed platform if developers were suddenly given reign over users' mobile screens.

However, two months ago or so, a certain curiosity, a thirst for a new challenge and a feeling that I was missing a boat (to where I did not know) combined to make me go out and buy an iPod touch (I don't want to buy an iPhone because my current phone deal is too good to give up). I almost immediately appreciated both what a well-designed platform it is and what a compelling playground the third-party application market represents, for users and developers alike.

9 September 2008

Tofu 2.0.1

Tofu 2.0 was released yesterday, which allows reading simple PDF documents, has a less obtrusive full-screen mode, supports scrolling on MacBook trackpads and is a Universal Binary (that is, it includes a native build for Intel Macs). An alpha version with most of these features had been available for quite some time, but it had some bugs, and it only recently dawned on me how to solve the trackpad problem.

I have since released revision 2.0.1, which fixes some bugs in yesterday's release.

In case you don't know what Tofu is: it tries to make reading text on the screen more pleasant by wrapping it into columns, which you navigate from left to right without ever scrolling vertically.

Go and get it here.

7 May 2008

The science of keyboard design

The Handbook of Human–Computer Interaction, edited by Martin Helander, Thomas Landauer and Prasad Prabhu, is a book published in 1997 that attempts to summarise research relevant to the design of interactive software and hardware. Its 62 chapters fill 1500 pages and provide advice on a multitude of topics, covering analysis, design and evaluation of interactive systems, as well as the psychological and ergonomic underpinnings of human–computer interaction. One of those chapters is titled Keys and Keyboards and was written by James Lewis, Kathleen Potosnak and Regis Magyar. It considers virtually every imaginable factor involved in designing keyboards, and, by drawing from experimental studies, provides recommendations for each of them. Ever since I read this chapter a couple of years ago, I've been meaning to summarise some of their conclusions and to consider them in the context of modern keyboard design. The recent string of keyboard-related links on Daring Fireball (e.g. here, here, here, here, here and here) moved me to finally sit down and do it, so here it is.

5 May 2008

Hyphens, dashes, et cetera

I have a thing about correct punctuation, and although I'm aware that most people would find me over-zealous in this regard, I would bring to my defence that it's not just a pointless obsession or a purely aesthetic matter. A bit of poor punctuation will in the best case distract those from the text who notice it and affect their impression of the author, and in the worst case actually give the reader trouble understanding a sentence. Having said that, what I'm going to write about today is more on the aesthetic side, but could nevertheless help you make a good impression on a reader who notices these things.

27 December 2007

Surface computing, move over!

For a few weeks now, my two team-mates at work and I have been using a “horizontal” whiteboard, lying across the desk surface between us. I had been wanting to try this for a while, but it wasn’t possible because of our previous desk arrangement. Now that we have this large area of space between us and no partitions, this small whiteboard fits perfectly without getting in the way.

Horizontal whiteboard setup

We’ve found ourselves using it virtually every day, illustrating explanations, walking through calculations and brainstorming design ideas. Visitors will intuitively pick up a pen and start using the whiteboard when explaining things. It somehow seems to invite people to use it more than most whiteboards. However, it’s not only a collaborative tool: it also makes a great scratch-pad when you’re brainstorming on your own. To ensure that it stays useful, we make an effort to keep the board clean; nothing tends to stay on there for longer than a day or so.

Overall, it’s being used far more than any wall-mounted whiteboards we’ve had near us, and I think this is due to two key differences to wall-mounted boards. Firstly, each one of us can reach the board very easily without having to get up. You just turn your chair slightly and there it is. Secondly, the whiteboard is between us, so it feels less like a presentation aid and more like a collaborative work surface, accessible equally well from all sides.

If your work involves collaborative problem-solving, and if your desk arrangement allows it, I highly recommend setting up a whiteboard like this. Don’t make it too big, because you won’t be able to reach all corners and it will also eat into your desk real-estate. I think ours is 90×60 cm, which is just right. I also recommend investing in some pens with a finer tip than the standard ones you tend to get. Those are designed to be visible from a few meters away, but you’ll find them too thick for handwriting at a comfortable size for close-up work. Edding do quite a range of dry-erase board markers.