RetouchPi Opens Camera RAW: DNG, NEF, ARW and RAF, Tested

A browser has no maker's decoder, so a RAW reader can only take one of three roads. The difference is not speed; it is whether what you get is the data that came off the sensor.

• It develops the file itself. DNG is an open container, so the sensor data can be read directly: the demosaic, the white balance and the tone curve are all computed here, and what you get is a picture derived from the sensor. All three measured DNG files took this road, including Apple ProRAW from an iPhone, which is a DNG.
• It falls back to the camera's own preview. RAF, NEF and ARW are proprietary containers: the sensor data cannot be read, but the camera wrote a full-size processed JPEG into the file when it shot. The editor lifts that one out and tells you, in the same moment, that it is a preview - with the dimensions.
• It refuses, by name. A CR3 keeps its preview as an HEVC video frame, which a browser image decoder cannot read. You do not get an empty canvas and it does not guess: the reason goes into the notice and the document is left exactly as it was.

Every timing and every pixel count below was measured on 2026-10-09, on one machine, in one bundled Chromium, run back to back - not copied out of a spec sheet.

On the second road you do not get undecoded sensor data; you get the picture the camera already computed: full size, demosaic done, the body's white balance and tone curve applied. The pixels are real - 6048 x 4024 is 6048 x 4024 - but the colour is the camera's decision, not something you can recompute from the raw data.

• What you can do: crop, curves and levels, local work, layers and masks, type, export - everything you would do with a full-size picture, and it is already the colour the camera itself endorsed.
• What you cannot do: redo the demosaic, change the white balance and still recover detail in the highlights, or pull back shadows two stops under. Those need the sensor data, and the sensor data needs the maker's decoder.
• How to tell: the notice says so. No notice means it developed the file; a notice about the camera's own preview means the second road; a notice with a reason means it was refused. In none of the three do you have to guess.

Falling back to the preview is not a failure; it is the ceiling of what a browser can do. It is written down here because it decides whether that file is a negative or a deliverable - as a deliverable it is enough, as a negative it is not one.

A RAW file has no special status once it is open: it is a bitmap document, and the rest of the editor makes no exception for it. Fifty-four tools, layers and layer groups, masks and channels, curves through to levels, ten layer styles, and up to 256 undo steps.

• The 50-megapixel DNG does not have to be scaled down before you can work on it: the canvas ceiling is 64 megapixels and 30000 px on the long side.
• To keep it layered, use File ▸ Save as PSD: it writes layered, and masks, blend modes and layer styles all travel with it.
• To keep the whole unflattened history, save the project file (File ▸ Save Project, Ctrl+S).

Every export lives in the File menu, grouped by what the file is: image, vector and page, video, layout. A RAW file mostly uses the first two - TIFF to keep the quality, JPEG and WebP to ship it, PDF for a single page, PSD to save it back layered.

The colour position, stated plainly: exports are sRGB at 8 bits per channel. 16-bit PSD and TIFF files open, and narrow to 8 bits on the way in; this version has no CMYK working mode, produces no plates and has no press-proofing step - a formal four-colour print job is not what it is for.

• CR3 will not open. The notice is quoted above: the preview is an HEVC video frame and a browser image decoder cannot read it. For that file, start with the maker's own converter.
• It does not decode proprietary sensor data. NEF, ARW and RAF go through the embedded preview, and this page does not pretend that is a develop.
• PSB and 32-bit files are refused by name, not silently dropped.
• HEIC is a different matter. It is not a RAW file, and whether it decodes depends on the platform the browser runs on: WebKit-based browsers decode it at full size, while desktop Chromium builds (Chrome included) say by name that they have no HEVC decoder.
• There is only one privacy sentence here: ordinary retouching - decoding, editing, exporting - stays on your machine, and AI generation and AI edits are the only step that reaches a server.