GRKit is an experimental, SD-card-based software tool (no firmware flashing required) that expands the creative options on Ricoh GR III, GR IIIx, GR IV, and their HDF variants (plus limited support for the GR IV Monochrome). It adds live-preview film looks inspired by stocks such as Kodak Portra 400, Kodachrome 64, Fujifilm Velvia 100, Tri-X 400, and others (with the option to import your own .cube LUTs or Lightroom presets), expanded framing and aspect ratios including the classic XPan 65:24 panoramic crop along with 2.35:1, 16:9, 4:3, 1:1, and more (with composition guides), plus effects like adjustable grain, bloom, red-orange film-style halation, and date imprint. After a simple copy-to-card install and a short load time on power-up, these features appear in the ADJ menu as “GRK” and in a dedicated MENU section; removing the card instantly returns the camera to stock behavior, making it fully reversible (though it is experimental and used at your own risk).
Here is a video describing GRKit:
