How to make lens corrections in Lightroom
Here you can find some easy tools to make corrections. In previous versions of Lightroom there were some tools, but starting from Lightroom 5, there are some more powerful tools to help you correct your images, like getting rid of keystoning and chromatic aberrations.
Keystone distortion is what happens when you point a camera upwards at a vertical surface with the top of the film plane tilted away from the building. Imagine that there are two parallel vertical lines on this surface. with the top of the film plane further away from that surface than the bottom of the film plane the two lines will no longer appear parallel, but will appear to converge as they run towards the top of the surface as viewed. This type of distortion is corrected by making the film plane parallel to the surface.
The reason it’s called Keystoning is the resemblance of a rectangle to the stone at the top of an arch. This stone has sides that are similar to an upside down triangle although the angle is much less acute. Anyway this stone supports the entire arch, thus Keystone. A rectangle, like an office building, shot from below with the lens tilted up will take on this shape.
Lens rise will minimise or remove this distortion, but keystoning &/or “falling over backwards” can add a sense of drama and impact to a photograph of a building, so don’t close your mind.
Chromatic Aberration, also known as “color fringing” or “purple fringing”, is a common optical problem that occurs when a lens is either unable to bring all wavelengths of color to the same focal plane, and/or when wavelengths of color are focused at different positions in the focal plane. Chromatic aberration is caused by lens dispersion, with different colors of light travelling at different speeds while passing through a lens. As a result, the image can look blurred or noticeable colored edges (red, green, blue, yellow, purple, magenta) can appear around objects, especially in high-contrast situations.