Smoothing out a sky in combined panoramas

Last night I did a panorama cityscape by combining eight photographs of mid-town Manhatten taken from across the East River. One of the problems dealing with so many images, especially when the sky is smooth and cloudless, is that the panoramic stitching software often delivers blotchy results  in the sky tones when putting the images together. That happened to me last night. Attempting to smooth out such a large area of constant tonality is not a fun post-processing task.

The time-exposure photos were taken with the 42mp Sony A7RII camera and Leica-M 135mm APO Telyt lens at f/8. Lately, I have been using PTGui program to combine the panoramas, but this time the results were so blotchy from the eight photos that I decided to go back and give Photoshop's photomerge a try.

The photomerge feature in Photoshop CC has been considerably improved. While it took much longer to complete the merge, the results were well worth the time. The sky was much smoother in its transitions than the sky produced by PTGui.

The resulting image file is 600MB and 7' wide. The detail from the 42mp sensor is incredible.

This panoramic of the city from across the East River showing the Empire State Building, Chrysler Building, and United Nations is a merger done in Photoshop from a combination of eight vertical images.

Even in the tiny photo assembled in PTGui you can see the variegated results in the sky tones from one side of the panorama to the other. 

These are the original eight vertical images that were combined to form the panorama.