RF 14-35 and cropping

Stein Rune Risa wrote:

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So to my question:

I understand that the correction of mechanical vignetting involves some cropping to remove the dark corners. But does this mean that it actually is not 14 mm? Or is it really "wider than 14 mm" and the cropping takes it down to 14 mm? Will I get the picture that I frame in my viewfinder - or will it be somewhat cropped?

Not the lens you're talking about, but with the RF 16mm f/2.8 you can't switch off the distortion correction in the camera and what you get is the field of view a 16mm rectangular projection lens, whether you use in-camera jpeg or export from DPP4. It's the same, almost to the pixel, as the field of view given by the EF 16-35mm f/4 set to 16mm.

(You can see better how photo editors correct barrel distortion if you import a photo into the GIMP and expand the canvas before adjusting the distortion. The original rectangular image ends up with parabolic (or 3rd order or higher) concave curved sides, and the largest rectangle you can crop out of the shape gets longer than the original.)

With DxO PhotoLab 5, the angle of view the program gives with its standard distortion correction is a little bit wider than that given by DPP4. (Same number of pixels, so DPP4 must magnify and crop more.)  It's closer to a 15mm than a 14mm field of view by my calculation, assuming DPP4's 16mm field of view is correct. I can even get a bit wider, 13½mm equivalent field of view, by cropping to 16:9, which is pretty amazing for such an inexpensive lens.

As a practical example, I put the camera on a tripod and photographed a mill with a 12mm lens, the 16-35mm EF lens, the 16mm RF lens and (without moving the tripod, an M100 + 11-22mm), then exported jpegs from both DPP4 and PhotoLab, superimposed them as layers in the GIMP, sizing and moving them to match, then drawing round each image to show the coverage. Here's the result.