Note: The images in this review were shot in raw and processed to taste using Adobe Lightroomm 5 Beta and exported to JPEG. Changes have been made to exposure, highlights, shadows, clarity and vibrance, but no noise reduction has been applied.
Fujifilm’s X-Trans sensor is a unique piece of technology with strengths and weaknesses quite apart from the usual digital sensor, thanks to its lack of an optical low-pass filter, and the novel RGB array designed to mimic the randomness of film grain.
The X-Trans sensor first appeared in Fujifilm’s X-Pro1, the company’s first mirrorless system camera and the second camera in the X-series after the X100. Previously, the X100 had a standard APS-C sized CMOS sensor with a conventional optical low-pass filter (although the camera's sharp images had many speculating that it was a weak filter). The X100S’ sensor is labeled X-Trans II, so it should be based on the original X-Trans sensor but not the same one found in the X-Pro1 and X-E1.
Thanks to the X-Trans II sensor, the X100S produces excellent 16MP images, but not without some caveats. First, the good: Colors are rich and deep, and the f/2 lens delivers sharp results with beautiful bokeh. Pictures are full of minute details, more than you'd get from a conventional sensor, thanks to the lack of the optical low-pass filter. ISO performance is exemplary, this little camera produces images at high ISO with less noise than even some APS-C DSLR cameras. You could shoot up to ISO 4000 with very little noticeable noise, and up to the native limit of ISO 6400 if you clean it up later in post.
Now, the bad: There’s something odd going on with the X-Trans array. Because of the more random arrangement of RGB pixels and the larger number of green pixels compared to red and blue, the image processing engine has to do more guesswork at determining the exact color of the light hitting the pixels. This has led to a color smearing effect in some images, where the color from one subject smears into an adjacent subject. It can also lead to a watercolor-like effect and edge halos on back-lit subjects, a phenomenal we first observed in our review of the X-E1.
Because of the X-Trans sensor’s unusual layout, imaging apps like Lightroom also have problems converting the raw data. In our experience, that leads to odd image artifacts, where the subjects sometimes look like they have double outlines, or smudged textures. Apparently, Fujifilm is working directly with Adobe to improve ACR’s (Adobe Camera Raw) ability to read X-Trans files - which is remarkable, as it’s the first Japanese camera company we’ve heard of doing that - but while Lightroom 4.4 handles X-Trans raw images better, it still doesn’t do as well as the camera’s own JPEG engine in reducing the number of artifacts.
To be clear, this is Adobe's challenge, not Fujifilm's, but seeing as how many photographers prefer to shoot raw and use Lightroom, it's also a workflow challenge for potential owners.
It's a toss up between shooting in JPEG or raw right now, but if it were us we'd still save in raw, because the X100S' raw files shine. The amount of dynamic range captured inside an X-Trans file is amazing, elements we thought were completely blown could still be recovered inside Lightroom. While the X100S' JPEG in-camera noise suppression can be quite aggressive, leading to overly smoothed textures, you can do a much better job yourself with the original raw files. However, another odd quirk we encountered with the raw files is that Lightroom will show that none of the RGB channels are blown, even though there are highlights in the image which are completely devoid of detail.
To be fair, the occasional edge halo, texture mottling and odd fringe artifacts might not bother you if you’re not printing images large or pixel-peeping. At its best, the X100S produces vividly luminescent images which glow with depth, color and detail, you’ll just need to know that the good results come with quirks.