Max quality needs darktable
Export offers two engines. Fast is built in. Max quality runs darktable, a separate free program, and the dialog says so when darktable is not on this Mac. This page is for that row, and for the two things Max quality refuses to do even with darktable installed.
The two engines
In the Export dialog, under Engine: Fast is Core Image — fast, and exactly what you saw while culling. Max quality is darktable-cli — the finest raw detail, but bakes from the raw file; slower, and only RAW frames gain. A JPEG or HEIC has nothing left for it to work on.
Needs darktable, the external RAW engine — Install…
Without darktable, the Max quality row reads this instead of a time estimate, and it cannot be selected. Click the row anyway: Vixlo opens darktable's download page in your browser. (If the browser will not open, the link is put on your clipboard, and the message saying so is hard to see here; see The browser will not open from the app.)
Install darktable, then close and reopen the Export dialog. The row checks again every time the dialog opens; there is nothing to restart.
Where Vixlo looks
Vixlo looks for darktable-cli in three places: Homebrew's folders (/opt/homebrew/bin and /usr/local/bin) and inside the darktable app in your Applications folder (/Applications/darktable.app). The download from darktable's own page goes into Applications; Homebrew's brew install --cask darktable lands where Vixlo looks too. A darktable kept anywhere else is not found.
Installed, but the export fails
A freshly downloaded darktable that has never been opened is held back by macOS until you approve it, and the export then waits on an approval nobody can give. After two minutes on a frame Vixlo gives up on that frame and moves to the next. The dialog at the end is then titled Export complete — with gaps, counts the frames that could not be rendered — see export-manifest.json for why, and shows how many were rendered and how many failed. Open export-manifest.json in the destination folder and the reason is there for each frame. For a frame darktable never finished, it reads Could not render DSCF0100: darktable-cli did not finish within 120s — a quarantined install hangs on Gatekeeper; open darktable once to approve it, with the exported file's name, without its extension, where this example has DSCF0100. Open darktable from your Applications folder once, approve it when macOS asks, then export again.
To spare the second run the frames that already worked, choose the same folder as the first time, not a new one, and leave Rename and Subfolder empty: files Max quality already wrote are then reused rather than rendered twice, and only the failed frames are rendered. The folder Vixlo suggests in the picker is a new one, named with the date and time, so choose the first run's folder yourself. With a Rename or Subfolder pattern typed, every take is rendered again beside the first run's files. Max quality and darktable has the rules.
Any other failure inside darktable is recorded the same way, with the last lines of darktable's own message as the reason.
Max quality refuses graded takes
If any take you are exporting carries a develop setting — a film simulation, a look, or an edit — Max quality refuses the whole export before anything is rendered, rather than deliver some files graded and others not. The dialog is titled Couldn't export. Its sentence opens with how many of the frames carry develop settings, and goes on:
… (a film simulation, look or edit) applied, and Max quality can't apply them — it would silently deliver ungraded files. Choose Fast instead, or reset those frames to their original look first. Nothing was rendered.
darktable is an outside program with no way to take Vixlo's develop settings. To export a graded shoot:
- Press Close. The Export dialog comes back with your settings as you left them.
- Under Engine, choose Fast.
- Press Export to folder… and choose the folder.
Try again is not the way out: it asks for a folder and runs the same export again, Max quality and all, and is refused again. If you specifically want darktable's RAW handling, reset those frames to their original look first, then export with Max quality.
What Max quality leaves out
Max quality takes the format, the quality, the Full, 4096 and 2048 sizes, and the Rename and Subfolder patterns, because Vixlo builds those names itself. It does not take the Colour space choice: darktable writes in its own default colour space, so Display P3 does not reach it. It does not take the watermark, or a preset's short-edge, megapixel or percent sizes. Those are the Fast engine's. A hand-written preset's long-edge size is rounded to one Max quality knows: 2048 or less becomes 2048, up to 4096 becomes 4096, and anything larger becomes Full. What it carries, and what it does not has the whole table.