Digital Photography Technology

HDRI photography or better known as, “High Dynamic Range Imaging” is a technique that lets a photographer achieve an extremely wide range of intensity levels between light and dark in a single photograph. HDRI photography is done by bracketing a number of exposures and tone mapping. All the exposures are taken on a tripod, and by changing the time of the exposure.

HDRI photography  was developed in the 1930’s by Charles Wyckoff.  It wasn’t until 1993 that a mathematical theory was developed for exposed images of the same subject and producing a single image. Computers and digital photography are making the process easier to manage.

Tone mapping reduces the dynamic range of a picture to a limited dynamic range so as to appear more natural in a print or on a monitor. The main object is to get detail in the highlights and also in the shadow or dark areas.

There are two types of tone mapping operators, global and local. Global operators map every pixel in the same way. This is a simple method, but some contrast can be lost. Local operators use an algorithm that effects each pixel separately, but taking into account the immediate surrounding pixels. The output is provides the best performance, but can look unrealistic at times.

Techniques for taking a HDRI photograph are basically simple. Any camera with an adjustable shutter speed will work, but a DSLR that takes a RAW image is the best. The RAW image offers maximum detail.

A quality stable tripod is must. The photo is taken of the same scene, but with different time exposures. DO NOT change the F stop. This will change the depth of field. Also, leave focusing on manual.

The first shot will be the best exposure. Then one stop under exposed and one stop over exposed. Three shots are the minimum. From there you can go to 5,7, or 9 shots. Always the same number under exposed and over exposed.An example of  5 exposures would be:

Photo # +2: 1/500@f/2.8<p>

Photo # +1: 1/250@f/2.8<p>

Photo #  0: 1/125@f/2.8<p>

Photo # -1: 1/60@f/2.8<p

Photo # -2: 1/30@f/2.8<p>

You are now ready to take your first HDRI photos. Select a subject that has shadows and bright areas.

After taking the photos, you are ready to sit down at the computer. The latest version of Photoshop and Photomatix are two software programs that will do an excellent job of HDRI. Photoshop includes HDR. Go to File, Automate, Merge to HDR, and you can start.

Photomatix is a stand alone program

HDRI Photography is a method of combing multiple photographs into one high definition photograph.