Showing the seaplane bases on the south side of YVR. This is shot at 50mm (75mm 35mm equiv).
X marks the spot where the Seair plane turned for its run-up and the green roof at far left is where the other shot shows the plane getting up to speed.
The Sigma 50-500 has excellent reach and good sharpness at 500mm. For example, you can see a Harbour Air DH2 Beaver at its dock in the centre of the photo; its the smaller plane on the right. Compare to my zoomed in shot.