The e-reader market has lost some of its initial appeal due to the rapid rise in popularity of tablets and other similar mobile devices. However, 'tablets' with E-Ink screens continue to offer the best reading experience in terms of reducing eye strain as well as providing long battery life. E-Ink screens have not scaled well in size, with the 6" screen size being the most popular and economical choice. Products with bigger screen sizes such as the Kindle DX (9.7") have not enjoyed market success.

E-Ink - A Brief Background

We will not go into the technical details of E-Ink here, but it suffices for readers to know that E-Ink avoids the use of backlighting. Instead, it relies on reflection from ambient light for visibility. In the latter aspect, it is very close to real printed paper. The major downside is that the refresh rate of E-Ink screens is very slow and only the monochrome technology is mature enough for mass consumption in the e-reader market.

E-Ink screens have been trying to evolve in two different ways. On one hand, we have attempts being made to get some sort of color display with E-Ink characteristics. On the other hand, E-Ink is trying to bring out flexible displays as well as produce larger sized screens. While screens of up to 32" in size are available for digital signage purposes, the maximum size currently supported for direct-to-consumer sales is 13.3".

The Need for a 13.3" E-Reader

Most of our workload nowadays involves sitting in front of a computer monitor and/or staring at tablet/smartphone screens. It is common for people to experience eye fatigue due to these activities. Having used multiple tablets and phablets for content consumption, I realized that none of them fit the bill when it came to reading technical documents or annotating them for future reference. In addition, all these technical documents are typeset in either A4-sized (8.27" x 11.69") or US Letter-sized (8.5" x 11") pages. This ruled out usage of any of the large number of e-readers based on the 6" E-Ink platform. A4 and US Letter correspond to diagonals of 14.3" and 13.9" respectively. 13.3" with an aspect ratio of 4:3 is ideal for displaying documents typeset in either A4 or US Letter-sized pages.

The Sony DPT-S1 - A 13.3" E-Ink Device

Sony's Digital Paper System (DPT-S1) was launched in April 2014. It takes things to a whole new level by making use of a 13.3" E-Ink Mobius screen. It was launched with a price tag of $1100, and was quite unpalatable for the ordinary consumer. It comes with a stylus / pen for taking notes as well as PDF annotation, and business users are its main target.

Initially, my impression was that lower priced variants with the same screen would soon appear in the market and target the average e-reader. Unfortunately, we are at the end of 2015, and the Sony DPT-S1 remains the only E-Ink Mobius-based product that consumers can purchase in the market. A little bit of silver lining lies in the fact that Sony has steadily been bringing the price down (from $1100 at launch to $800 right now).

The Sony DPT-S1 comes in a nondescript box. The package consists of a quick start guide, the e-reader in a leather sleeve, the pen / stylus, three replacement tips for it along with a tool to aid in pulling out the old tips, and a 7.5W (5V @ 1.5A) USB charger with a USB to micro-USB cable. The gallery below provides high-resolution pictures of the various components.

As can be seen from the gallery above, the main reader is like a sheet of white paper surrounded by a thick bezel. The bottom bezel is slightly thicker to accommodate the navigation and context menu buttons at the center with the power button at the right corner. The power button is on a slanted panel and is not flush with the rest of the frame - this prevents accidental pressing of the power button during use.

The important aspects of any e-reader are the dimensions and the weight. While the unit as a whole comes in at 9.125" x 12.125", the viewable area / screen is 8" x 10.625" (corresponding to a diagonal size of 13.3"). Note that this needs to be compared to an A4 sheet (8.27" x 11.69") and a US Letter sheet (8.5" x 11"). The viewable area is slightly smaller than both of them, but definitely much better than the 9.7" E-Ink screensfor documents typeset with those page dimensions.

The weight of the reader alone is 355g, while the stylus/pen adds an extra 9g. Placed in the supplied sleeve, the complete package weighs in at 496g. All said, the unit is quite ergonomic to use - both in hand, as well as on a table. The screen has a pixel resolution of 1600 x 1200 and can display 16 levels of grayscale. It is likely that most use-cases for the DPT-S1 involve text-heavy documents. The DPI and color limitations are not much of a concern.

In the rest of the review, we will take a look at the hardware platform in detail and follow it up with a look at the software aspects before providing some concluding remarks.

Hardware Platform

In the previous section, we had a brief description of the external hardware aspects of the Sony DPT-S1. A few aspects not noted over there include the presence of a microSD slot on the back as well as a micro-USB charging / data transfer port just beneath the navigation / context menu buttons at the bottom. The microSD slot can accommodate microSDHC cards up to 32GB in size. The back panel also includes a reset hole that can be activated with a pin while booting up to restore the device to factory conditions.

Thanks to a forum member over at mobileread, we have some insight into the internals of the system. The pictures linked in the forum are reproduced in the gallery below.

The board shots reveal the following components:

1. Freescale i.MX508 application processor (single core Cortex-A8 at up to 1GHz)
2. Samsung LPDDR2 K4P8G304EQ x32 8Gb (1GB) DRAM
3. SanDisk 4GB eMMC 4.51 19nm flash (SDIN7DP2-4G)
4. Wacom digitizer
5. Neonode zForce NN1001 optical touch controller

In addition, the FCC ID printed in the back (VPYLBWN572) indicates the presence of a Murata WLAN module which internally uses a Atheros AR6003G 1x1 802.11b/g/n 2.4GHz radio-on-chip WLAN controller.

The stylus / pen supplied as part of the DPT-S1 is passive. It doesn't need any batteries. No recharging is necessary. The Wacom digitizer is also passive in nature. According to a forum post on mobileread, it is possible to use non-Sony digitizer pens with the DPT-S1. This indicates that Wacom's EMR (Electro-Magnetic Resonance) technology is in use. The power requirements for EMR are satisfied by the display side. The digitizer generates a magnetic field that allows energy inducement in the pen's resonator. This can, in turn, be detected by the digitzer to determine the coordinates of the pen's position and its orientation.

The DPT-S1 has a touchscreen with multi-touch support. The teardown reveals an optical touch controller. The DPT-S1 integrates a set of light emitters and detectors along the edges of the screen and an optical light guide to the neonode touch controller IC. The IC controls the light sent out and also monitors the detectors. Changes in lighting conditions can indicate the presence of a touch object. The coordinates can also be calculated by the IC once calibration is in-place.

The device contains a rechargeable Li-ion battery rated at 3.7 V DC, 1270mAh. With the supplied 5V @ 1.5A USB charger, Sony indicates that full charging can take up to 2.5 hours.

Coming back to the general characteristics of the hardware, we find that the rear side of the device is a fingerprint magnet despite not being glossy. The front screen itself, thankfully, is not that bad. The navigation and context menu buttons make an audible click when pressed. While this is good feedback, there appears to be a lack of consistency across the three buttons in terms of the force required for activation. The placement of the power button in a slanted panel works perfect, but some users might prefer the power button elsewhere. The placement of the micro-USB port is unfortunate in the sense that the device has to be taken out of the sleeve for charging purposes. All these are minor aspects in the overall scheme of things.

The physical characteristics of the E-Ink Mobius screen (8" x 10.625" with a 13.3" diagonal, 1600 x 1200 resolution and 16 levels of grayscale support) have already been discussed. Readers might be wondering if a 13.3" tablet would be a good alternative if the backlighting / eye strain issue is not a big problem.

The above photograph shows the same graphics-heavy PDF page displayed on a Sony DPT-S1 and a Dell Inspiron 13 7000 series in tablet mode (13.3" 1920x1080 touchscreen). Despite the absence of color capabilities, it is obvious that the aspect ratio of the DPT-S1 leads to a better experience with the perusal of the content.

Software and UI Aspects

The Sony DPT-S1 runs a Linux kernel, but the user interface shows no signs of Linux running under the hood. The setup process is quite straightforward - the time zone, date, pen grip style and an user name are the minimum required things to get started with the unit.

The main screen is organized in two panes. The smaller-width left pane provides the main options - a 'Home' view, 'Documents', 'Note', 'Workspace', 'Web Browser' and 'Settings'.

The 'Documents' section allows users to explore the file system (local storage as well as network drives) for PDFs. The 'Note' section allows for creation of handwritten notes (they are saved as PDFs).

The 'Workspace' section enables users to open a set of documents and group them for easy retrieval at a later time.

Available settings include user name configuration, Wi-Fi configuration (the standard scan, WPS and manual configuration options). Under server settings, one can set up a WebDAV account for syncing with the internal storage in the DPT-S1. While most users tend to use Box.com for this purpose, I decided to take advantage of the WebDAV features in my local QNAP NAS. Various application preferences (including those for the web browser) are also available, as shown in the gallery above.

It is also possible to calibrate the pen input to make sure that the writing appears at the correct place on the screen. The button on the pen can also be configured as an eraser (default) or highlighter. Firmware can be updated either from within the device (OTA) or by connecting to a PC.

The web browser built into the firmware is passable. At short notice, it is possible to navigate to known download links and obtain PDFs instead of hooking the unit to a PC and transfer the downloaded file via USB. As of v1.5, it is possible to block pop-ups, enable or disable JavaScript.

The PDF viewer allows pinch to zoom, but the extent of zooming available is not close to what is available on PDF readers on PCs. The photographs below show the zooming function in action. PDFs can be annotated with the stylus / pen and they are visible when the same PDF is viewed on another device also. While annotating, it is possible to use either blue or red color (appears as different grayscale shades on the DPT-S1, but in the proper color on other devices), and the text can either be bold or normal.

Graphics-heavy PDFs do take some to load, but, once loaded, navigation and zooming have acceptable speeds.

Writing notes with the pen / stylus takes some getting used to. After a few scribbled notes, I was able to get the hang of things. It is possible to adjust the thickness of the lines as well as the color of the text. The software also allows the various toolbars, tabs, side menus etc. to be hidden. This allows maximum use of available screen estate for the document.

Since the DPT-S1 targets professionals, the firmware is quite stable and bug-free within the set of available features. We do have some suggestions for improvements in our concluding remarks.

Concluding Remarks

The Sony DPT-S1's feature set and pricing make it clear that business users are the primary target market. Posts on various e-reader forums indicate that the device is gaining popularity amongst academics and lawyers. Despite the business / enterprise focus, there is nothing preventing power users from using it as a standard e-reader. In fact, the device, when used in the landscape mode with a two-page thumbnail view (a feature introduced in firmware v1.5.50.1180 released on December 15, 2015), can simulate holding a real book with two pages side by side. The availability of a pen / stylus can also lend itself to some interesting applications for casual users. Writing on the plastic surface of the Sony DPT-S1 feels closer to writing on actual paper compared to glass surfaces in other tablets.

Sony DPT-S1 - Not Necessarily an 'all work, no play' Device

Even though I try to avoid printing out documents / papers and read them on a computer monitor or tablet, I can't totally avoid the usage of a printer. Since purchasing the Sony DPT-S1 a couple of weeks back, I haven't printed out a single document. One of the aims of the Sony DPT-S1 is to reduce paper clutter. I have to say that it succeeds nicely in this respect.

Coming to the business end of the review, we will analyze the pros and cons of the Sony DPT-S1 first.

On the plus side:

• The unit is lightweight, yet solid. The experience is very similar to carrying a folder with a few sheets of paper.
• The unit has great ergonomics and is perfectly size for technical documents
• It is a great vehicle to bring out the advantages of E-Ink
  • No strain on the eyes, thanks to the absence of backlighting
  • Visibility under bright light / outdoor environments is perfect
  • The battery life is great - more than a couple of weeks between charges even with regular use (2 - 3 hours a day with a page or so of writing on each day)
• Annotation capabilities with the pen input is great for note taking and other business uses.
• It reads all PDFs - no messing around with DRM, no proprietary file formats, no 'cloud' accounts needed
• Combination of features make it a very unique product in the market

On the other side:

• The exorbitant pricing ($800) makes it unsuitable for personal use. There exists better value for money if an E-Ink screen is not a must
• The PDF viewer could do with some more features to make it more versatile / suitable for non-business use-cases. (more zooming, adjustable cropping to remove white margins etc.)
• Firmware, in general, could do with some extra features - such as providing additional options for network shares along with the currently existing WebDAV support.
• Limitations of E-Ink
  • Low refresh rate can hamper user experience when redrawing the screen during document navigation / zooming
  • Absence of color capabilities
• Adding audio capabilities could help expand the addressable market (targeting audiobooks, for example)
• At the $800 price point, the presence of just 4GB (3GB usable) of internal flash is disappointing. Availability of a microSD slot alleviates this issue somewhat.
• A more powerful processor could help in providing a better user-experience with graphics-heavy PDFs.
• Absence of contrast adjustment (something possible in the Kindle-DX) is a bit disappointing
• There is no built-in light for reading in the dark (something available in the Kindle Paperwhite)
• Wear-out of the pen tips could be a worry for heavy users
• Navigation buttons at the bottom could do with a more pronounced feel. The current design (flush with the rest of the frame) is more suitable for capacitive touch-based implementations.

Despite the list of potential improvements and drawbacks being longer than the positives, the Sony DPT-S1 gets my recommendation for being a unique product in a specific niche. Products based on the 13.3" E-Ink Mobius screen have also been shown at tradeshows by companies like Netronix and Pocketbook, but they remain vaporware.

If the characteristics of E-Ink screens fit your requirements and you need a size-for-size replacement for traditional paper documents, the Sony Digital Paper System DPT-S1 is the perfect fit. It does a surprisingly great job despite being the only such product in the market. We hope Sony continues to provide firmware updates for the product and bring the price down even further.