The image sensors in most digital cameras use what is called a “Bayer" color filter array. From Wikipedia:
A Bayer filter mosaic is a color filter array (CFA) for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, camcorders, and scanners to create a color image. The filter pattern is 50% green, 25% red and 25% blue, hence is also called RGBG, GRGB, or RGGB. It is named after its inventor, Bryce Bayer of Eastman Kodak.
Fuji X-Trans sensors, on the other hand, use a proprietary filter pattern inspired by traditional film. X-Trans color filters are randomized in a way that negates the need for an optical low pass filter, increasing resolution and sharpness while also improving color accuracy. From Fuji:
Learning from our experiences in traditional photography we arranged the patten of red, green and blue photosites on the surface of the Fujifilm X-Trans sensor in a more random manner than in conventional Bayer array sensors. This minimises moiré effects to the point that the X-Trans sensor does not need a low-pass filter, which, in turn, boosts resolution and sharpness. The X-Trans CMOS's 6 x 6 pixel pattern also ensures that colour reproduction is better than that achieved with an ordinary Bayer array. All horizontal and vertical lines contain at least one R, G and B pixel whereas Bayer array sensors do not have R and B in some lines resulting in false colour reproduction.
Unfortunately, this unique design causes all sorts of problems for conventional raw processing software. Because almost all raw processors are optimized for the more common Bayer sensor arrays, Fuji RAF raw files can be difficult to work with. Noise reduction and sharpening routines in particular, must be drastically modified to take full advantage of RAF files. This can be quite daunting (and frustrating) for photographers accustomed to working with raw files from Canon, Nikon, and other Bayer-type cameras. Using typical noise reduction and sharpening routines with RAF files often results in worm-like artifacts and halos (see above), particularly in high frequency detailed areas that contain dense foliage, grass, and other natural textures.
Adobe has been particularly slow in developing acceptable RAF demosaicing and sharpening algorithms for their popular Lightroom and Camera Raw applications. They have improved somewhat over the the past couple of years, but they still lag behind many of their competitors in this area. This is a major cause of frustration within the Fuji community because so many of us depend upon Lightroom as our primary tool for processing and cataloging raw files. The good news is that there are alternatives that provide much better demosaicing and sharpening results while still allowing the use of Lightroom for other steps in the image processing pipeline.
My favorite raw processing tool for initial demosaicing, import sharpening, and other global adjustments of RAF files is Iridient Developer. Iridient is a free-standing raw processor that can also be used as a plugin within Lightroom. It produces far better detail, clarity, and corner sharpness than Lightroom, while still allowing the use of Lightroom for other tasks. Here’s my typical workflow:
- Import the RAF raw files into Lightroom.
- Select the image to edit and choose “Edit in Iridient Developer” in the “Photo” menu in Lightroom. This creates a copy of the image in Lightroom and opens the RAF file in Iridient.
- Apply noise reduction, sharpening, and other global adjustments in Iridient as needed.
- Save the file from Iridient using the "Process image and overwrite (Std Image)" command in the "File" menu. This replaces the copy created by Lightroom with the new file.
- The newly created TIF containing the edits from Iridient is now stacked with the source RAF in Lightroom.
- Continue further processing of the new file in Lightroom.
Using Iridient as a plugin within Lightroom requires some setup. Details about how to setup both Iridient and Lightroom to use the above workflow are available on the Iridient website.
Once this is all setup, the workflow is not much more complicated than working strictly within Lightroom. The results are outstanding though, and well worth the small added effort. If you’re currently processing your Fuji RAF files strictly within Lightroom, I’d highly suggest giving the above workflow a try.