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A .pef is fine until it has to leave your desk. Upload forms reject it, browsers will not render it, and a client on Windows opens nothing. Convertessa decodes each file locally and writes a JPG at the same pixel dimensions, at a quality you choose for the run. K-mount and 645 medium-format files take the same path, and the originals are read but never rewritten.
Before anything else, check your camera's file-format menu. Pentax bodies let you write DNG instead of PEF, and most owners never touch that setting. PEF is Pentax's own TIFF-based container with a losslessly compressed payload; DNG is Adobe's open format, and everything that reads raw reads it. Converting a backlog of .pef files is a perfectly good reason to be here — but you can stop producing new ones tomorrow.
For the files you already have: macOS will show you a .pef in Quick Look, and that is roughly where the format's welcome ends. Upload forms reject it, browsers ignore it, and a colleague on Windows is stuck. Convertessa hands the image work to libvips, whose raw decoder reads the Bayer mosaic, applies the white balance the camera recorded, and writes sRGB. That last part deserves its own sentence: Pentax sensors capture colour well outside sRGB, and the JPG boundary clips it, so a saturated maple or a deep cyan sky can come back a shade duller than the same file in Digital Camera Utility.
A Pixel Shift PEF is four exposures, each offset by a single photosite, stored together so every pixel receives real red, green and blue instead of interpolated values. General-purpose decoders typically render the first sub-frame and leave the other three alone. The JPG is then an ordinary demosaiced image at normal resolution — correct and usable, but without the colour accuracy that made you turn the mode on. When a Pixel Shift frame matters, merge it in Pentax's own software first and convert that export.
Also left behind: the Custom Image profile (Bright, Natural, Monochrome, Reversal Film), in-camera distortion and vignetting correction, and 14-bit tonality flattened to 8. The PEF decode itself is lossless — every bit of loss in this conversion happens at the JPG encode, which is the part the quality setting governs.
Drag a folder of .pef files onto Convertessa; K-series and 645Z files can share one queue. Approve the image engine install on first run and it is there for every batch after that.
Pick JPG and set the quality for the run. One value applies to the whole batch, so split web exports and print-grade exports into two passes when you need different numbers.
Convert. Each file is demosaiced, encoded to an sRGB JPG and written beside the original or into the output folder you name, while the .pef files stay exactly as the camera wrote them.
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Worth considering. Pentax bodies offer both in the file-format menu; DNG is read by essentially every raw-capable application, while PEF sometimes needs a decoder that specifically knows the format. PEF files are usually a little smaller, and Pentax's own software is happiest with them. Either way it changes nothing about the .pef files already on your drive — those still need converting, and both formats convert the same way here.
Pixel Shift stores four exposures offset by one photosite each. General-purpose raw decoders normally render the first sub-frame and ignore the rest, so the JPG arrives as a normal demosaiced image at normal resolution — perfectly usable, but without the true per-pixel colour that Pixel Shift exists to produce. If that particular frame matters, merge it in Pentax Digital Camera Utility and convert the export it gives you.
Because Custom Image profiles — Bright, Natural, Monochrome, Reversal Film — are instructions the camera applies to its own JPEG, stored as a tag alongside the raw data. A neutral decode reads the sensor and skips the instruction. The converted file is therefore in colour and unstyled, closer to what the sensor actually recorded than to the preview you saw on the rear screen.
No. Distortion, lateral chromatic aberration and vignetting correction for DA and D FA lenses are applied by the camera to its JPEG, or by Pentax's software when it renders the PEF. The open-source decoder used here does not read those profiles, so the JPG shows the uncorrected optics. On a well-behaved prime you will never notice; on a wide zoom you might.
No. PEF's payload is losslessly compressed, so the decode recovers exactly what the sensor wrote. All of the loss in this conversion happens in one place — the JPG encode — which is why the quality setting is the only knob that changes the outcome. The other unavoidable change is depth: 14 bits per channel in the PEF become 8 in the JPG.
Yes, only the extension changes: IMGP0247.PEF becomes IMGP0247.jpg. Send the output somewhere separate so raws and JPGs never share a folder:
convertessa ./*.pef --to jpg -o ~/Exports --quality 92
Originals are read, never rewritten, so the sequence numbering your camera assigned survives intact and the JPG sitting next to a PEF is obviously the same frame. If two cards produced overlapping numbers, convert them into separate output folders.
Yes — the medium-format bodies write PEF through the same container, so the path is identical. The practical difference is scale: a 51-megapixel 645Z file is roughly twice the size of a K-3 III file and takes proportionally longer to demosaic. Large batches are still worth starting and walking away from, since the queue keeps every core busy while it works.