The new "Dehaze" adjustment in Lightroom CC 2015.1 is quite remarkable, and as the name implies can be used to dramatically reduce the appearance of haze in images captured under hazy atmospheric conditions. Increasing the value will significantly reduce the appearance of haze in the photo, and reducing the value will increase the appearance of haze in the photo.
More Detail:
I had previously referred to the Clarity adjustment in Lightroom's Develop module as the "haze buster", but I will no longer refer to it this way now that the Dehaze adjustment has been added to Lightroom. While the Clarity adjustment can certainly help reduce the appearance of haze in a photo, it is really focused on improving mid-tone contrast.
The "Dehaze" adjustment, on the other hand, is specifically focused on reducing the appearance of haze in a photo. Therefore, we can now simply think of the Clarity adjustment as being focused on enhancing texture and detail in a photo, while the Dehaze adjustment allows you to dramatically reduce the appearance of atmospheric haze in a photo.
The results of Dehaze are, in my experience, simply remarkable. If you are a Facebook user, you can see a sample image that shows the original photo, the effect of Clarity, and the effect of Dehaze. You'll find that image on the wall for my "Tim Grey Photo and Imaging" page here:
https://www.facebook.com/timgreyphoto
The Dehaze adjustment is found in the Effects set of controls. To reduce the appearance of haze in a photo simply drag the Amount slider for Dehaze toward the right. You can adjust the setting based on your own preference, without much risk of any serious problems in the photo. The only thing to keep an eye on is an overly dramatic appearance for the photo, with strong shadows and exaggerated contrast.
With a little practice you'll get a sense for how much of a Dehaze adjustment might be too much for an image. In some respects the issue here is similar to the processing of high dynamic range (HDR) images, where it is generally preferred to avoid the appearance of "over-processing" for the photo. But used with a degree of self-control, the Dehaze adjustment can create a dramatic improvement in many photos.
