Using the Sliders after Automatic
Now, most of the time clicking on Auto will produce good results. When it doesn’t, you can manually tweak the various sliders to get the results you want. It helps to check the Show Grid option on the bottom right to get a sense of how straight your angles are. You can also check the Preview option on the top right to see the differences before and after.
In our example, while the building in the middle is decidedly straight, the buildings to either side are still tapering. So we use the Vertical slider to make them look straighter.
But by doing so, the bottom edges of the image start to get cropped out, so we have to use the Scale slider to enlarge the image to fill the frame.
Once you get the effect you like, click on OK.