Hayward Lake - Using HDR

Bracketed photographs merged using Photomatix HDR software

HDR stands for high dynamic range.  It is a method of getting more latitude out of a scene than would otherwise be possible using conventional techniques.

A digital sensor has about 8 stops of latitude when shooting jpegs.  This means that the light coming from a dark area and the light coming from a bright area can be no more than 256 times brighter or darker than the other before details become lost.  Anything darker than this level of shadow appears black and anything whiter than this level of highlight is perfectly white.  Essentially what this means is that, in a high contrast scene, dark areas would be black with no details and bright areas would be white with no details.

If you shoot in raw mode, you can get around 12 stops of latitude, which gives a difference of over four thousand times between extreme dark and light where details can be distinguished.  This is much better for shooting in high contrast situations, and one of the main reasons why most advanced photographers opt for this capture mode.

If you need more latitude than this, or if you want to play with the range of highlights and shadows in a different manner than what a normal jpeg or ram image will allow, there is HDR.  I want to point out that many cameras come with an HDR feature, or you can use a program like Photoshop that has HDR ability.  My experience has shown both of these avenues generate less than great images in general.  I use a program created by Photomatix which allows me to produce an HDR image from multiple bracketed files or even from a single raw image.

The process is easy.  Shoot a number of images of your scene with your camera on a tripod.  Bracket (take several pictures with each one being overexposed, properly exposed, or underexposed) widely; I often do seven photos with exposure compensation values set to +3, +2, +1, 0, -1, -2, and -3.  I combine the images together into a single picture using the software and then make adjustments as necessary to obtain the effect I want.

You can also use only a single raw image.  Shoot the image the way you normally would then, in Photoshop, enter the raw processor and save the image several times, each time altering the exposure value of the program.  Again I will use 5 to 7 variations.  Plug them into the HDR software and off you go.  The advantage of using a single file to create an HDR photograph instead of many is that everything is in exactly the same place.  People, cars, wind blown flowers, and so or are each in the same position for every shot.  You will not likely be so lucky with a bracketed set.

It takes a modest amount of time and, if you take multiple photos, a large amount of memory, to do this.  If you are planning to make many HDR pics, bring extra batteries and memory cards because you will use up the existing ones quickly.