Phase detection pixels were installed in the APS-C 16 megapixels X-Trans CMOS Sensors to create the newly upgraded X-Trans CMOS II Sensor. By removing the low pass filter, its resolution was vastly improved, bringing out the full potential of the lenses.

More details can be found here

By distributing pixels containing three colors each (R/G/B) for all lines, both vertical and horizontal, color discrimination has been improved. Thanks to Fujifilm's unique interference reduction technologies, resolution is not lost when shooting at higher sensitivities, creating beautiful images with less interference.

The new X-Trans CMOS Sensor includes phase detection pixels to detect the distance from the subject, dramatically improving AF speed. This promises more ease of photography with a maximum speed of 0.08 sec.(*1)

*1 : High Performance Mode

More details can be found here

The Hybrid Viewfinder has been upgraded to high precision 2,360K-dots. Whether using the Optical Viewfinder or electronic viewfinder, both allow smoother shooting based on your needs. By placing a debris protection coating on the front surface of the viewfinder and adopting a dustproof structure on the inside, its durability was also improved.

This camera includes a function called “Focus Peak Highlight” which highlights areas of high contrast to aid in focusing. It also includes a feature unique to X100S called “Digital Split Image” function which is a first-ever accomplishment worldwide(*2) , which allows you to experience anew the joys of focusing. This allows for more delicate focusing when shooting, particularly with open aperture or macrophotography. Of course, there is also a standard mode included. Adjustments were made and the internal structure of the focus ring re-examined, to allow you to naturally sense the moment you come into focus with the moves of the focus ring.

*2 : Fujifilm research as of November 2012

More details can be found here

Multiple exposure photography lets you turn ordinary everyday scenes into works of art. With X100S, the Optical Viewfinder can be used in addition to the electronic viewfinder and LCD monitor. The image produced by layering the first photograph onto the second one is sure to stimulate your artistic sensibilities.

Filter techniques create eight different types of special effects. By choosing the optimal filter for your subject or scene, you can expand the range of expressions for your pieces. This provides more fun through photography while fully utilizing the latest technologies that only a digital camera can offer.

PRO Neg.Std and PRO Neg.Hi featured in interchangeable premium camera FUJIFILM X-Pro1 are also available in X100S. This allows for color reproduction and gradation expressiveness previously only found in film cameras. This camera also includes a bracket function which can be used at your discretion, for three types of film simulation in any shot.

Based on the requests received from FUJIFILM X100 users worldwide, X100S was upgraded to the full extent possible. From changes in viewfinder mode switch layout, viewfinder lever shape, AF button position, to re-examining the pressure required for the dials, many elements of the camera hardware were upgraded. Not only that, but also details such as multiple tabs for the GUI menu and ISO sensitivity setting methods were changed. All these revisions were made toward the goal of realizing a more usable camera.

With the separately sold wide angle conversion lens, shooting in 28mm (35mm format equivalent) is also possible. Photography at aperture value F2 can be used as-is for impressive premium resolution photography with no image degradation. The special leather case has also been upgraded, enabling the replacement of batteries and media without removing the case.

More details can be found here