High dynamic range (HDR) photography captivates viewers through its bedazzling attention to details and its stunning array of color. Rich and beautiful images created using HDR techniques directly responds to the age old problem of not being able to record what the eye can see. HDR overcomes this limitation and more.
From the earliest days of photography, the days when photographers created glass negatives using a mixture of silver nitrate and egg whites, photographers complained about being unable to record a scene on film as the eye sees that scene. Many photographers learned to master these limitations, think about Ansel Adams' Zone System for black and white photography, learning to manipulate exposure with filters, film sensitivity, developing processes, and much darkroom gymnastics. The result was, and remains, stunning imagery. For amateurs and serious hobbyists, however, found themselves fighting against murky shadow detail and washed out skies. The struggle was real even for the seasoned professional.
The problem originates in the real world. The dynamic range of what the eye can see across the visible spectrum is enormous. Our eyes evolved to see the entire range from deep shadow to bright highlight and everything in between. Capturing that range on film or using a digital sensor presents one with an efficiency problem. Film, digital sensors and the techniques for printing not to mention computer monitors, are simply not up to the task of capturing detail across a wide dynamic range. HDR photography changed all that forever. Photographers using HDR techniques are now able to capture light across the widest dynamic range with relative ease.
What is this dynamic range I keep referring to? In its simplest terms the dynamic range refers to the variation in luminance from the brightest to the darkest light values in any given exposure and high dynamic range photography refers to the ability to capture light across all or most of the dynamic range of the scene being photographed. HDR is accomplished by exposing from 3 to 7 bracketed exposures across a range of f-stops and/or shutter speeds and then recombining those exposures into a single merged image which now reflects exposures made for highlights, midtones as well as shadows.
Every bracketed image contributing to a finished HDR image inputs important information about the image being created. Underexposed images contribute to highlight detail while overexposed images provide information about the shadows. When combined, the bracketed exposures produce an hdr file that contains all of the information necessary to produce the hdr image. A second step, often referred to as tone mapping, converts the hdr file into a usable image that may then be saved as a TIFF or JPEG file. The tone mapped image is the one that is most useful when we print an HDR image. The tone mapped image displays the full range of color and detail in both the shadow areas and the highlight areas while holding the midtones true and rich.
HDR doesn't just happen. This should come as no surprise. No photography, at least not good photography, ever just happens and HDR is certainly no different. Long before the first picture is taken one must have a good feel for the technical aspects of the equipment being used. Knowing how to successfully bracket, how many exposures to make and what intervals are appropriate for a bracketed series is important. Knowing how to manage images on your computer is a boon to speeding your workflow as you process your images. Paying attention to the details of HDR goes a long way to helping you create rich HDR images.
Is HDR perfect? Heck no! It is appropriate for some but not all conditions, it is not appropriate for all subjects. In fact, most subjects that display a large degree of motion are generally not candidates for HDR photography. But when the conditions and subjects are right, HDR solves many dynamic range problems.
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