Sometimes it’s a good idea to do a sequence of pictures of a scene instead of a single shot. During that sequence you change a specific parameter from picture to picture. The camera has to stay in position while taking the sequence, so use a tripod or put the camera on a stable object. The finally merged picture should have an increased quality over the single shot. There are two common scenarios, one is the exposure bracketing and the other is the focus bracketing.
Exposure bracketing
The problem you want to fix is happening if parts of the scene are out of the limits of the dynamic range of your camera sensor.
Dynamic Range
The dynamic range is the range between the brightest and darkest tones a camera sensor is capable to differentiate. Everything brighter than that is just white and everything darker is just black. You will get an impression of that if you take a single shot of a scene with a part in the sun and a part in the shadow. Depending on the chosen exposure you will either have a black section in the part in the shadow, a white section in the part in the sun or even both.
HDR vs. AEB
A way to fix that issue is to do a sequence of photos with a changing shutter speed and then merge them into one. If this merging happens by the camera itself it’s called HDR (High Dynamic Range) and if the photos getting stored separately it’s called AEB (Auto Exposure Bracketing) and you have to merge them with a post-processing tool afterward.
Focus bracketing
The problem you want to fix is happening if the object of interest is out of the max. suggestive depth-of-field of your camera lens.
Depth-of-field
The depth-of-field is defined by the opening of the aperture of the camera lens. The deph-of-field is the section that is in focus and the rest of the scene is out of focus. If the aperture is closed quite much you have a huge depth-of-field, but especially in macro photography you get diffraction quite fast. If that happens you have to lower the F-Stop, but then you possibly won’t get the whole object of interest in the depth-of-field.
Focus bracketing vs. Focus stacking
A way to fix that issue is to do a sequence of photos with a changing focus point and then merge them into one. If this merging happens by the camera itself it’s called Focus stacking and if the photos getting stored separately it’s called Focus bracketing and you have to merge them with a post-processing tool afterward.