Processing techniques for Fuji RAW files, or how to avoid “worms”

Why write this blog post?

One topic that comes up regularly in Fujifilm community groups is methods for avoiding sharpening artefacts (aka worms) when processing Fujifilm RAW files. A debate that comes up frequently is whether using Capture One or Adobe Lightroom does a better job when processing Fuji RAW files.

An example of worms-like artefacts after processing a Fuji RAW file incorrectly.

This blog post intends debunking some of the myths associated with Fujifilm RAW files and their processing. I will keep technical details as light as possible and I will not be comparing each individual software in details, as this would require a dedicated review or blog post. I also believe that choosing the right software comes down to personal preferences and needs, with image quality and workflow speed being high up on the long list of decision criteria.

I know from experience that both Capture One and Adobe Lightroom can produce comparable results when processing Fuji RAW files, having used them both successfully. I will also explore Fujifilm’s X RAW Studio, as this software is provided for free to Fujifilm users.

What’s so different about Fuji RAW files?

As you may know, Fujifilm X series cameras use APS-C sized X-Trans sensors. The majority of other camera manufacturers use Bayer sensors. These sensors differ mostly by the usage of different Color Filter Arrays (CFA) overlayed on the sensor. In very simplified terms, the two sensors have different CFA patterns, as can be seen in the organization of the Red, Blue and Green (RGB) filters, on top of the sensor’s photosites:

X-Trans filter array

Bayer filter array

Since the filter arrays are different on X-Trans and Bayer sensors, processing the RAW files from both sensors require different algorithms for correcting colors and exposure levels. Since each pixel in the filter array only captures one color, the missing colors have to be interpolated from other surrounding pixels to obtain a complete (r, g, b) triplet. This is done using a demosaicing algorithm, unique to each type of sensor. The Fujifilm X-Trans RAW files are generally considered more complex and more intensive to demosaic correctly.

Each photo editing software has its own demoisaicing algorithm for the various sensors, and this is where we can start seeing some differences when processing RAW files from different camera manufacturers, particularly Fujifilm. This can lead to images having differences in perceived sharpness, in reproduction of colors and in rendition of image/sensor noise. This demosaicing process is generally the source of unwanted, worm-like image artefacts.

For more details about the X-Trans sensor demosaicing and a very thorough comparison between Capture One and Lightroom, I strongly recommend this long but excellent video from Oliver Hilbert.

Debunking the myths

Myth #1: Capture One is better than Lightroom for Fuji RAW files

A common misconception is that processing Fujifilm RAW files in Adobe Lightroom invariably produces worms, and for that reason using Capture One is the way to go when you want to process Fujifilm RAW files. This is plain and simply not true.

Worms are the result of incorrect demosaicing and sharpening steps in your workflow, which are not unique to Lightroom. From experience, I can attest that you can get worm-like artefacts using Capture One if you process the files incorrectly.

Also, such unidimensional statements lead new Fujifilm users in making time consuming and financially costly decisions, sometimes deciding to change their image organization/processing software. I know first hand as I attempted converting my Lightroom catalog and workflow over to Capture One, and I ended up going back. For additional details on this, please read my other blog post detailing my journey between LR and C1.

Myth #2: Worms only really matter if you are a pixel peeper

Another misconception is entertained by diehard fans of Lightroom, this time. According to them, the presence of worms in your pictures only really matters if you are a pixel peeper, examining your photos at 200% or above magnification on a computer screen. In my opinion, this compromise is simply unacceptable. The demosaicing of RAW files is part of the photographer’s workflow, it is something he/she has control over. Why would any serious photographer choose to voluntarily degrade their work?

By introducing imperfections at the very first steps of your processing, you are introducing deficiencies that will be compounded by subsequent editing steps in your workflow. The whole point of using software like C1 or LR is for their non-destructive editing capabilities.

A best practice is also to future-proof your work ; you never know how you might want to use an image in the future. What if you wanted to produce a large print of one of your images, for personal or commercial use? Would you succeed convincing a client that the worms are contributing to picture quality? You absolutely want to preserve maximum image quality for each and every photograph you invest time in processing.

Myth #3: I just wished Fuji used a Bayer sensor

Well … actually this is not really a myth. I sometimes wonder if the benefits of using an X-Trans sensor actually outweighs the drawbacks. It is strange to consider that Fujifilm uses Bayer sensors in their low-end and medium format (GFX line) cameras. Why maintain the added level of complexity of X-Trans for part of their lineup, with questionable benefits? This complexity not only impacts Fuji’s R&D process, it also transfers to Fuji photographers indirectly, having to deal with the intricacies of correctly demosaicing X-Trans RAW files.

For a detailed comparison of the X-Trans and Bayer sensors and their rendering, I recommend this article from Jonathan Moore Liles at PetaPixel.

Demosaicing Fuji RAW files like Obi-Wan

In the interest of keeping this article short, I only included three softwares in this analysis. I did not include solutions like Luminar AI, darktable or RawTherapee, that can also process Fujifilm RAW files, as I do not have sufficient experience using them. When I tested them, some of these options did not maintain consistent color accuracy through my editing workflow (importing, exporting, publishing). Make sure you perform advanced testing with your own images and workflow before committing to an image editing and organization solution.

Fujifilm X RAW Studio

Fujifilm X RAW Studio is the default option available for processing X-Trans RAW files. This software uses the camera’s RAW processor and demosaicing algorithm to convert sensor data into a digital image in JPG format. It is leveraging the same image processor that is used when shooting in JPG or RAW+JPG format directly in camera.

While an excellent option, you will certainly need to use X RAW Studio in combination with a second image editing software, as it only provides RAW processing capabilities.

Pros	Cons
RAW files processed with X RAW Studio will look exactly the same as the JPG files produced by the camera.	Camera needs to be available and plugged in to process the RAW files.
Native support for Fuji film simulations.	Limited feature set ; does not provide advanced image editing or organization capabilities.
Software is free.	Cannot process RAW files from other camera manufacturers, if you were to own multiple camera systems.
Excellent performance, as the image processor and algorithms on the camera are optimized.	Output format is limited to JPG, which is a compressed format. If you intend doing additional processing, this could reduce final image quality.

Capture One

Capture One provides an excellent demosaicing algorithm for X-Trans RAW files. You don’t need to think about it much, it does a good job out of the box. Capture One Express For Fujifilm is also provided for free, although it lacks some of the more advanced features of the paid version, like cataloging images and advanced masking (see this feature comparison).

While extremely powerful, Capture One can be a little of a handful to master, the learning curve is steep. It is also still catching up to Adobe Lightroom with regards to image cataloging features.

Pros	Cons
Excellent demosaicing algorithm for Fuji X-Trans sensor RAW files.	High license cost for the paid versions.
Powerful image editing features.	Some features feel inferior to Lightroom, like image organization and import/export performance.
Navigating images feels fast, even on lower-end hardware.	Some useful features not available on Express version.
	Support for multiple cameras is only available on the Pro version, which is even more expensive.

Adobe Lightroom Classic

Adobe Lightroom is one the most well known photo editing software on the market. Is has excellent image cataloging and editing functionality. Unfortunately, Lightroom’s default demosaicing algorithm, for X-Trans RAW files, is to be avoided as it introduces unwanted image artefacts. This is particularly visible on high ISO images.

There are however alternatives available in Lightroom to demosaic Fuji RAW files correctly:

• You can use the Enhance Detail functionality in Lightroom, which uses a different demosaicing algorithm and uses AI processing to recover image details and color information.
• You can use Iridient X-Transformer, an additional paid utility, as a plugin in Lightroom. X-Transformer uses a proprietary demosaicing algorithm and provides additional features like sharpening, lens correction and noise reduction.
• Both methods produce a separate DNG file (digital negative) which can be further processed in Lightroom. This unfortunately requires additional storage space, as DNG files are larger than the original RAF files coming out of Fuji cameras.
• I recommend this video from photographer and youtuber Reggie Ballesteros, where he compares the various methods for processing Fuji RAW files in Lightroom. I personally prefer the rendering of Enhance Details over X-Transformer.

I wish that Adobe presented demosaicing of X-Trans RAW files in a more intuitive way, perhaps as an additional step in the import flow. For a vanilla user, there is absolutely no way to understand that the default X-Trans demosaicing is inaccurate in Lightroom, other than learning the hard way.

Pros	Cons
Powerful image cataloging and image editing features.	Additional step for demosaicing X-Trans files using Enhance Details or X-Transformer. It requires processing time and additional storage.
Better overall value than Capture One considering you get Photoshop, cloud storage and Portfolio bundled with the subscription.	Navigating and editing images can be sluggish on lower-end hardware.
Availability of Lightroom Mobile and Web.	High license cost and only available on a subscription.
Provides support for all major camera RAW formats, which is useful if you own multiple cameras from different brands.

Final words

As you can see, there is a lot of hidden knowledge and misconceptions around processing of Fujifilm X-Trans RAW files. The reality is that all software solutions presented in this blog post are viable solutions for obtaining excellent image quality from your Fujifilm files. They all have different strengths and weaknesses.

I want to re-emphasize the fact that software selection goes beyond the demosaicing algorithm used. Choosing the right image editing suite is a personal decision, influenced by the needs and workflow of each individual photographer. As such, it is extremely tricky to make recommendations to random strangers on the Internet, as you are missing a lot of the extra context needed for making an informed recommendation.

While I certainly have a personal preference for Adobe Lightroom, I recognize and respect that other photographers might prefer other options. What is ultimately important is the comfort level, workflow speed and image quality you obtain from your image editing application.

For additional perspective, please read my other blog post detailing my experience using Lightroom and Capture One.

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