Fujifilm GFX100RF:
B&H Photo / Amazon / Moment / Adorama
A newly published patent (JP-2025-178957, published Dec 9, 2025) has surfaced, giving us a fascinating look under the hood of the GFX100RF. While we have been enjoying the camera since April, this filing reveals exactly how Fujifilm’s engineers managed to fit a medium format lens into such a compact body.
However, the patent contains a second optical example that is raising eyebrows: a 28mm lens that does not appear to cover the medium format sensor at all.
The second example in the patent describes a 35mm f/4 lens with an image height of approximately 28.2mm. This perfectly matches the GFX sensor (which requires a roughly 27-28mm image height to cover the semi-diagonal).
This confirms the optical DNA of the GFX100RF. The design utilizes a back focus of just ~5.4mm, allowing the rear element to sit virtually on top of the sensor. This ultra-short distance is what makes the camera so thin compared to GFX interchangeable lens bodies, but it necessitates the fixed-lens design with a built-in leaf shutter.
Here is where things get interesting. Example 1 in the filing details a 28mm f/4 lens.
Initially, one might assume this was a wide-angle concept for a “GFX100RF Wide.” However, looking closely at the data, the image height (Y) for this lens is significantly smaller than what is required for medium format.
The image circle in Example 1 appears closer to Full Frame (36x24mm) or potentially a very aggressive APS-C projection. If this lens were mounted on a GFX sensor, it would likely produce massive mechanical vignetting.
There are a few possibilities for this “mystery lens”:
For now, the patent serves as confirmation of the brilliant engineering in the GFX100RF, while leaving us with a very interesting breadcrumb regarding Fujifilm’s R&D into other sensor formats.
via J-PlatPat
