This article describes how to process X3F files, a file format developed by SIGMA specifically for FOVEON sensor images, using both the official development software “SIGMA Photo Pro” and the image processing software “Affinity Photo,” and compares the results.
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Table of contents
- What is a SIGMA X3F RAW file?
- What is Affinity Photo?
- What is SIGMA Photo Pro?
- Summary
- Development result comparison
- Reference links
What is a SIGMA X3F RAW file?
SIGMA X3F RAW files are an image format exclusive to Sigma’s SD and DP series cameras. These cameras are manufactured by the Japanese company Sigma. This special format directly saves the RGB three-layer image data captured by the Foveon sensor.
As of 2026, cameras equipped with the latest Foveon sensor, the Foveon X3 Direct Sensor (generation name: Quattro), such as the dp2 Quattro (released in 2014) and later models, now allow users to select the more versatile DNG format for recording captured images.
However, the X3F format, which separates and saves three colors, is likely to remain popular due to its ability to process updates through software advancements. Since the X3F format has remained consistent, X3F files taken with older cameras can be processed with the most recent SIGMA Photo Pro software.
Furthermore, DNG images generated by Sigma cameras are larger than X3F files. In 2017, the image processing software SILKYPIX announced that it would support X3F files; however, the description states that it only supports the SIGMA dp Quattro series (dp0 Quattro, dp1 Quattro, dp2 Quattro, and dp3 Quattro). Therefore, it is unclear whether it can be applied to older X3F models.
What is Affinity Photo?
Affinity Photo is image editing software available for Mac, Windows, and iPad. It features various RAW file development capabilities.
Its RAW file development function supports all X3F files used in Sigma’s SD (SD9, SD10, SD14, SD15, SD1, SD1 Merrill, SD Quattro, and SD Quattro H) and DP (DP1, DP2, DP3, DP1 Merrill, DP2 Merrill, DP3 Merrill, DP0, DP1, DP2, and DP3 Quattro) series cameras.
As of 2023, Affinity Photo 2 has been released, and I purchased it through an Affinity campaign and am now using it. However, I haven’t noticed any significant differences in X3F development compared to version 1.0.
AFFINITY Photo offers two RAW processing engines: Serif Labs and Apple (Core Image RAW).
Details on processing are described in the processing result comparison.
What is SIGMA Photo Pro?
SIGMA Photo Pro is the original X3F development software provided by Sigma when the SIGMA SD9 was released. The SD9 features the FOVEON X3 sensor.
Versions 6.8.4 and later of SIGMA Photo Pro support native operation of Apple M-series chips. As of May 2024, the latest version is SIGMA Photo Pro 6.8.5. However, it does not support developing DNG files, which became available with the Quattro series.
After acquiring a Mac mini with an Apple M-series CPU in May 2024, I tried running SIGMA Photo Pro 6.8.5. The latest CPU’s power is impressive; I no longer experience SIGMA Photo Pro’s sluggishness. At the same time, the development speed increased, and my motivation to use SIGMA Photo Pro returned.
In SIGMA Photo Pro, you can change the file output destination and various options in the preferences menu.
I apologize for initially finding the software difficult to use due to my unfamiliarity with its operation methods, such as selecting the output folder. However, the computers I used in the past lacked sufficient processing power, so I didn’t feel motivated to use them extensively enough to become proficient.
When the SIGMA SD9, the first camera equipped with a Foveon sensor, was released in 2002, Intel Pentium 4 and AMD Athlon XP processors dominated the computer environment. The operating system was Windows XP (32-bit); CPU clock speeds were around 1 GHz; and memory was around 512 MB. Therefore, processing approximately 10 MB of data (3 megapixels x 3) was challenging.
Even more than ten years later, in the 2010s, when I was using SIGMA Photo Pro on Windows 10 and Intel Macs, the Foveon sensor’s pixel count had increased to 10 megapixels x 3. However, SIGMA Photo Pro was still slow and unstable and frequently crashed.
However, since becoming compatible with Apple Silicon in the 2020s, SIGMA Photo Pro has been stable and performs well with an M2 Pro + 32GB memory setup.
The ease of developing X3F files is largely due to advancements in computer technology. If the Foveon sensor had evolved alongside computer advancements, development would likely not be so challenging.
Unfortunately, sensor evolution has stalled since the Quattro medium format sensor of the 2010s, despite the significant improvement in the X3F development environment due to increased machine power.
Foveon sensors and Sigma cameras always seem to be out of sync with the times.
Summary
Affinity Photo is image processing software that can perform development work. However, it cannot display thumbnails of images in a folder. Additionally, because X3F uses a unique file format, thumbnails cannot be displayed in the viewfinder or Explorer. Therefore, if you only shoot with X3F, you will need to use SIGMA Photo Pro to view the images in the folder. The inability to display thumbnails is one of Affinity Photo’s weaknesses.
While it is inconvenient to not be able to complete everything with a single software program, the software is stable. It is easy to use, although this may depend on your familiarity with Affinity.
As will be discussed later, Affinity Photo’s default settings produce a strong raw image, which may make you want to extensively change the settings. However, making too many changes can result in false colors and image degradation, making it more difficult to achieve the desired balance of adjustments than with SIGMA Photo Pro. You will need to practice extensively to find your preferred settings.
The RAW development function is reportedly available in the free version that will be released after 2024, so you may want to try it if you are interested.
In March 2024, Canva acquired Affinity. Hopefully, Canva’s policies will not change the direction of the software.
SIGMA Photo Pro uses a standard method to display images in a folder as thumbnails. You select the files you want to process and then develop them. Since it’s the official software, automatic processing produces reasonably good images, and subsequent fine-tuning is easy. Furthermore, it allows for the consistent processing of X3F files. The fact that the software itself is free is also beneficial.
While usability has improved compared to previous versions of SIGMA Photo Pro as of 2026, development and software response speeds could still be improved upon compared to other commercially available image processing software.
Development result comparison
Affinity Photo is one of the few software programs capable of processing the challenging X3F images, so I compared its development results with those of SPP 6.8.5.
Since both software programs have a wide range of parameters, the test involved using the Apple engine for Affinity Photo’s development engine and the default settings used at the time of shooting for SPP 6.8.5’s development results to see if they could be made to a certain extent similar.
- Raw-X3F images from a DP3 Merrill were used for the test. The parameters used during shooting were as follows:
- When you use the auto-correction function in SIGMA Photo Pro, it adjusts parameters such as contrast using SIGMA’s algorithm. It tends to increase the overall contrast to create a more visually appealing image.
- However, the auto-correction function doesn’t always align with the photographer’s intentions. If you’re not satisfied with the results, you can use them as a basis for further corrections or revert to the default settings and adjust them.
- Compare the default loading state of Affinity Photo and SIGMA Photo Pro.
- The image on the left is Affinity Photo and the image on the right is SIGMA Photo Pro.
- The default settings are compared below. Affinity Photo has a good exposure, but the image is mild and sleepy. On the other hand, SIGMA Photo Pro is overexposed overall, with white and black clipping. Also, the cat’s redness is strong, and the image is sharp.
- As can be seen in the enlarged image below, the SIGMA Photo Pro image (on the right) is overexposed compared to the default Affinity Photo image (on the left), with darker blacks and some detail lost. SIGMA Photo Pro’s sharpness is also evident in the rendering of the hair.
- As shown on the left, the exposure in SIGMA Photo Pro was set to -0.8 to salvage the crushed blacks in the image below. Affinity Photo remains at its default settings, as shown on the right.
- Lowering the exposure reveals that, while the crushed areas are still visually obscured in the SIGMA Photo Pro image, some detail remains.
- I increased the sharpness in Affinity by 50%. However, I’m more concerned about the black levels than the sharpness.
- I adjusted the black point in Affinity to +7%, which improved the blacks. However, when I zoomed in, false colors became noticeable in some areas.
- I’m struggling to decide whether to continue with this approach or start over from scratch.
- If you understand the correction strategy and how the parameters change in Affinity Photo, it seems possible to produce images similar to those produced with SIGMA Photo Pro. However, since SIGMA Photo Pro is the manufacturer’s own software, it likely has expertise in enhancing sharpness and suppressing false colors, which are key features of Foveon sensors.
- It’s also necessary to investigate whether the parameters confirmed in test images using Affinity Photo are applicable to all images. As SIGMA Photo Pro becomes more user-friendly with sufficient computer power, the need for third-party software like Affinity Photo diminishes.
Reference links
- Affinity-Raw-Help-documents
- SILKYPIX X3F development
- SIGMA X3F Plug-in for Photoshop®
- SIGMA Software Download
- Foveon and SIGMA’s “Meme”・SIGMA press release
- Can the free “Affinity” software save digital camera users suffering from the “Adobe tax”? It might help with tax savings.・IT media news article
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Update history
- 2026.6.1
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