HDR stands for High Dynamic Range. The dynamic range of an image is the scale between darkness and light. The dynamic range of a normal photo is limited. Depending on exposure, different parts of the actual dynamic range are revealed: a low-exposure photo lets you see the highlights, but the shadows are blacked out; a high-exposure photo lets you see the shadows, but the highlights are whited out. An HDR photo lets you see the whole spectrum of brightness, from the brightest to the darkest.

In order to create an HDR photo, you need several photos of the same object with different exposure. Some cameras have the option to automatically do this, so check your manual. If your camera doesn’t have this option, you can still adjust the exposure manually (but make sure to use a tripod). 3 photos should be enough in most cases.

The best program for HDR is the strangely-named Qtpfsgui. This program is free and works better than many commercial HDR creation programs.

Once you download and launch the program, click 

New HDR and then open the images you took. Select “auto align images”, and then click next. It will take some time for the program to align the images with each other. After that, you will get a manual alignment screen, giving you an opportunity to correct any mistakes the program may have made (which is rare, but still possible).

The next step will show you some options. It is usually best to leave them as they are and click Finish.

Once the image is processed, you will see it, along with some options on the top frame (”Mapping”, and “Histogram”). They will let you preview how the image will look with different settings, but they won’t have an effect on the final result. The mapping mode that I think looks best is the “Linear” one. Once you are finished looking at the image with different settings, press “Tonemap the HDR” on the upper toolbar.

The Tonemap window has a lot of modes, each with their own settings. The ones I found to work best are the “Reinhard” ones. Be sure to experiment with the settings to find the ones which work best. Once you get a result you like, tonemap it with a high resolution, save it, and you are done.