Your files stay on your Mac.
Convertessa decodes each Canon CR3 on your Mac and writes a full-resolution TIFF: every photosite the sensor recorded, demosaiced once and stored losslessly at 16 bits per channel. Drop a card's worth of frames and the whole batch runs in a single pass. Nothing is uploaded, your CR3 files are opened for reading only, and the finished TIFFs land wherever you point the output.
CR3 is Canon's third-generation raw format, introduced with the EOS M50 in 2018 and now standard across the R system, the 90D and the 250D. Unlike the CR2 it replaced, it is built on the ISO base media container — the same box structure as MP4 — with sensor data compressed by Canon's CRX codec. One .CR3 is really a bundle:
Turning that mosaic into TIFF means demosaicing: interpolating a full red, green and blue value for every pixel from neighbours that each recorded only one colour. The decision is made once and baked in. What comes out is a rendered image rather than a raw file, so the highlight headroom and the penalty-free white balance you had in the CR3 do not travel with it. Keep the CR3s.
TIFF is lossless and holds 16 bits per channel, so nothing is discarded in the encode itself and gradients survive further grading without banding. It is also the format that print, scientific and archival pipelines accept without argument. There is no quality slider here, because there is nothing to trade: a TIFF is an exact record of the pixels it was handed.
Size is the first. A 45-megapixel R5 frame at 16 bits per channel is roughly 260 MB uncompressed against about 45 MB for the CR3, so budget disk space before batching a card. Colour is the second: Picture Style and Digital Lens Optimizer are camera-side instructions stored in the maker notes, not pixel data, so an independently rendered TIFF often looks flatter and more neutral than the preview you saw on the back of the camera. That is the raw file honestly rendered, not a fault.
Drag your CR3 files, or an entire DCIM folder, onto Convertessa. Frames from the R5, R6, R7, R8, R10, 90D and M50 are all read, and the originals are opened for reading only.
Select TIFF as the output. Because TIFF is lossless there is no quality slider to weigh up, and every frame is rendered at the full sensor resolution the camera recorded it at.
Start the queue and aim the output at a volume with room to spare. Each rendered frame typically runs five or six times the size of the CR3 it came from.
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No. Demosaicing and white balance are applied once, on the way out, and the TIFF records the result. The highlight headroom that was still recoverable inside the CR3, and the freedom to re-judge white balance without penalty, do not survive into a rendered image. Keep your CR3 files, because they are the negative. Think of the TIFF as a print you can hand to another program.
Because the preview was never the raw data. What the rear screen and Finder's thumbnail show is a JPEG that Canon rendered inside the camera with your Picture Style applied, contrast and saturation and sharpening baked in. Picture Style, Auto Lighting Optimizer and Digital Lens Optimizer are instructions stored in the maker notes rather than pixels, and an independent renderer does not apply them. The flatter TIFF is a more neutral starting point with more room to grade.
16 bits per channel, which is what makes this conversion worth doing. A CR3 holds roughly 14 bits per photosite, so an 8-bit output would discard most of the tonal range before you had touched the file. At 16 bits, skies and skin gradients survive further exposure and curve work without banding. Three channels at 16 bits is also the reason the resulting files are so large.
Roughly five to six times the card itself. A 45-megapixel R5 frame is about 260 MB as an uncompressed 16-bit RGB TIFF against roughly 45 MB as a CR3, so 300 frames is comfortably 70 GB. Aim the output at a volume that can take it:
convertessa ./DCIM/100EOSR5/*.CR3 --to tiff -o /Volumes/Work/Renders
There is no quality flag to reach for, since TIFF is lossless and --quality does nothing here.
No. Vignetting, chromatic aberration and distortion profiles are recorded in the CR3's maker notes for Canon's own software to act on, and an independent render leaves the frame as the lens actually drew it. Convertessa converts and does not crop, straighten or retouch anything. If those corrections matter to you, render through Canon's Digital Photo Professional, or apply a lens profile to the TIFF in your editor afterwards.
The as-shot value the camera wrote into the CR3 metadata, which is whatever you dialled in, or whatever auto white balance decided, at the moment of the exposure. It is applied during rendering rather than carried alongside the pixels, so correcting a badly judged white balance later in the TIFF is a colour adjustment on finished data, not the free, reversible change it would have been in a raw editor.
Yes. C-RAW is Canon's compact variant of the same CR3 container: the sensor data is compressed with some loss to roughly halve the file size, but the extension and the container structure are identical, so nothing about the conversion changes. The resulting TIFF is still 16-bit and full resolution. It simply started from slightly less information than a standard CR3 of the same scene would have carried.