Thursday, March 28, 2013

The importance of good dynamic range

In these color versions of the shoot of the Empire State Building from yesterday I was shooting the subject back lit on a very bright sunny day with no fill. Sensors in the newest DSLR cameras are good enough to be capable of covering a broad light differential where both extreme highlights and extreme shadows have detail. This is the dynamic range of a camera and is particularly important to landscape photographers or anyone working with harsh daylight. Dynamic range can be given as the number of f/stops a camera can cover and still maintain detail. This is sometimes referred to as EVs, or exposure values, where each EV represents one stop exposure difference of double the amount of light.

In the days of low ISO color slide film dynamic range was limited to about 1 1/2 stops. Many of the newer professional digital cameras, such as the Nikon D800 or D600, can now cover as much as a 14 stop exposure range. In some situations when shooting with a Nikon D800 I have been able to record the actual round shape of the sun and still have detail in the shadow areas in the same scene.

Recording extreme dynamic ranges still means doing some post processing to open up the shadows and bring down the highlights. But the important thing is that when this is done, detail is still present in these areas so they do not come out as pure white or pure black.

Another factor that will diminish dynamic range is using high ISO settings. For the best results it is important to keep a low ISO setting and keep the camera set as close as possible to its "native ISO" where it is calibrated to produce its best results.

You can use an HDR (high dynamic range) technique that combines several images each with a different exposure of the same scene. To do this, however, the camera must be on a tripod so that each exposure overlaps the other perfectly. This is not always possible in casual shooting. Personally, I find the many of the results of HDR photos to have a very false look, especially as it is a technique that is often overdone.

Taken with the new Nikon 18-35mm lens on a Nikon D600. The only difficulty of this shot was tying to line up the sun so it was peeking through the tiny space of the building and still have the full top of the Empire State Building framed in the window. A photograph such as this shows the excellent dynamic range of the new Nikon cameras when you consider that full tonality is held from the bright highlight of the sun and the back lit shadow areas of the buildings.
Here the foreground building was in deep shadow while the Empire State Building in the background was in open daylight. Nonetheless, full detail is preserved in both areas, and, although not quite apparent in this small, low res version, there is also detail in the bright sky.

The Empire State Building is framed by a window from inside the library, two very extreme lighting situations, yet full detail is preserved in both the brightest highlights and deepest shadows. Dynamic range does tend to decrease as ISO is raised so it is important to try and maintain a low setting whenever possible. It this scene the ISO was only 200. In the days of low ISO slide film a shot with this much detail would have been impossible.

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