This is a guest post from fellow photographer CJ Kern.
Let’s start off with a basic understanding of what HDR photography is; simply put High Dynamic Range (HDR) is a set of techniques that allows you to capture a greater dynamic range (lower lows & higher highs) than could be captured in a single exposure. In order to capture this higher range photographers take a bracketed set of photographs: some under exposed and others over exposed; usually something like this (-2, -1, 0, +1, +2).
Once you have taken your bracketed shots, how can you be sure you captured the entire range of your scene to make your HDR image is as robust as it can be? It is simple, check the Histogram on your camera. There is no need to check the histogram on all your images; the quick way to do it is to look at the darkest image in your series and see if most of the data is towards the left of your histogram (Fig. 1) then check the brightest image and see if most of the data is towards the right (Fig 2). If this is the case then all of the images will have filled the histogram, giving you the complete range of your scene.
The histograms shown in this example were taken from the shots I used to create the photograph “The Barber Chair” at Eastern State Penitentiary in Philadelphia, PA. When I bracket my shot I usually do so until, at a minimum, the data has moved away from the dark (left side) of the histogram. Knowing what I am looking for, I simply check the histogram out in the field to see if I captured a series of shots with all the details I need to create the HDR photograph I want. If the series did not capture enough data to fill the histogram I would have needed to add more brackets, (seven or even nine) or space each bracket further stops apart (-4, -2, 0, +2, +4).
Photo by CJ Kern. View the photo on Flickr.