The camera does not see the way the human eye does in a number of ways. One of these ways has to do with the brightness range of the subject. The human eye can see a much wider range of brightnesses than the camera. Brightness levels that exceed the camera's ability to see are rendered as pure white or black. With digital photography we have a number of ways of compensating for this limitation, one of which is called High Dynamic Range Imaging (HDRI, or HDR for short).
HDRI involves shooting a scene with a range of exposures, to encompass most or all of the scene's brightness range, and then combining these exposures with software to produce a single, low-dynamic-range image. In other words, the process compresses the scene's brightness range to make it fit within the photographic medium. How much compression of the brightness range the photographer uses depends on a variety of considerations, including (but not limited to) the display medium, the subject matter, the photographic genre (each of which has its own standards or conventions) and the photographer's aesthetic judgment.
In addition to enabling photographers to achieve a "realistic" rendering of a particular scene, HDRI allows photographers to achieve a wide range of special effects. When photographing building exteriors and interiors for documentary or marketing purposes, most professional photographers and their clients generally prefer a realistic look to the photographs.
HDRI allows photographers a tremendous amount of flexibility to create a very wide range of looks for their images. However, this flexibility tends to make the process very difficult to control. In addition, the process is prone to creating unintentional and unpleasant-looking artifacts, such as halos, muddy tones and garish colors that were not in the original scene. And, some scenes just do not lend themselves well to this process: simply being able to render most or all of the detail in a scene does not mean that the result will be a good looking photograph, however much Photoshop magic one tries to throw at it. It can sometimes take even quite experienced photographers quite a while to become comfortable with the process. Furthermore, there are highly experienced photographers for whom the process never achieves entirely satisfactory results, but I think this has to do mainly with stylistic considerations, rather than an inability to master the process.
HDRI has become very popular for real estate photography in recent years. Traditionally, to compensate for a very wide brightness range, architectural and interior photographers would use supplementary lighting equipment or modify the ambient lighting in some way by means of reflectors, covering windows, changing light bulbs, etc. However, these methods can be time consuming and can require a lot of expensive equipment, as well as an assistant to help set up the equipment. For standard real estate photography (that is, most real estate photography other than that done for larger builders or expensive luxury properties), there is not sufficient time or a sufficient marketing budget to allow for the full architectural and interiors lighting treatment. Furthermore, many real estate photographers do not have formal training in photography and have had little or no experience using lighting equipment. HDRI therefore seems like an easy way for real estate photographers to photograph buildings without using supplementary lighting equipment. Some real estate photographers even tout HDRI in their marketing as a new and superior photographic process, although it is neither new nor necessarily superior to more traditional photographic techniques.
Photographing buildings well for documentary and marketing purposes is one of the more difficult types of photography. Aside from the challenge of dealing with very high brightness ranges, there is frequently the challenge of dealing with highly uneven ambient lighting. The traditional lighting techniques of architectural and interior photography help deal with this kind of situation as well, and with digital photography we also have Photoshop to help with this. However, as powerful a program as Photoshop is, it cannot do everything; and, even when Photoshop can help with evening out the lighting, it can sometimes take longer to work this way than to deal with the situation on site with supplementary lighting. In fact, some real estate photographers have developed a technique of using multiple compact flashes placed around, and even hidden within, the scene, and with this method the more experienced photographers can achieve quite professional looking results with a high degree of efficiency.
As useful a tool as HDRI may be, it cannot by itself compensate for poor ambient lighting. Furthermore, generating the low-dynamic range image with the HDRI software is not the end of the process if one is trying to achieve high-quality results. Substantial Photoshop work is usually needed to mold what the HDR software produces into an appealing image. This can take a lot of time and requires a well-trained (or at least a talented) eye. In my opinion, many real estate photographers who are using HDRI exclusively, without using any means of modifying or supplementing the ambient lighting, are not putting much time into the Photoshop processing after generating the HDR image, and some appear to have not even spent much time learning how to get optimum results out of the HDRI software. The result of limited processing skills and no lighting skills is frequently images that are less than compelling for marketing purposes.
I think that HDRI is a useful tool, and I make use of this technique from time to time. However, for interior photography I mainly use supplementary lighting and Photoshop layering for contrast control, sometimes in combination with HDRI, but mostly without. In my opinion, anyone who photographs buildings for a living, and wants to do this at a reasonably high level, should have a decent familiarity with using supplementary lighting equipment. By supplementary lighting, I do not mean a single flash mounted on the camera. I mean multiple stand-mounted lights. For real estate photography this usually means compact flashes, although some real estate photographers use studio-type strobe equipment. Continuous, hot, light sources are usually only used for higher-budget types of architectural and interior photography, and of course for video and movies.