High Dynamic Range (HDR) Photography: Part 1

by Garry D. Gutterman

Posted: May 30, 2012

What is High Dynamic Range (HDR) Photography?

Simply put, Dynamic Range is the luminance value of a scene from darkest to lightest; from deepest shadows to sparkling highlights.

When shooting, we want to capture the dynamic range of the scene without blocking up the shadows or blowing out the highlights. We refer to this as the contrast range of a photograph. This is where the techniques of HDR photography come into play. In HDR photography we can bring back areas of detail that might be lost in a standard photograph’s shadows and highlights.

On the left is the image in its natural RAW state, on the right is the same scene in an HDR tone-mapped image. Notice that the HDR image is brighter and has almost a surreal look.

Think of it this way. The brain acts to interpret what the eyes can see. The eye’s iris rapidly opens and closes to take in the extremes of the deepest shadows and the brightest highlights, and the brain then combines these extremes so that we can see across the full dynamic range of the scene. The human eye has a dynamic range equivalent to approximately 14 f-stops. (Watch your friend’s iris expand or contract as they look at brighter or darker subjects; this is a mirror-image of the apertures of your camera.)

A camera-lens iris cannot do what your brain does since it has only one opening (f-stop) for each shot. Depending on how we set our camera to meter the scene, it will either expose for the shadows, highlights, or some mediation of the two, so that what we see in a standard photograph is not what our brain 'sees.' The average DSLR has a dynamic range equivalent to approximately 8 f-stops.

HDR photography allows us to see across the full contrast range that our eye can see, expanding from 8 to 14 stops. It does this by allowing us to combine seemingly underexposed and overexposed, as well as properly exposed individual shots of the same scene, and then putting them together to reveal the fullest possible range of tones and detail.  To clarify, the under-exposed shot may be under-exposed for the main subject of the image, but may be perfectly exposed for the highlights.  Similarly, the over-exposed image may actually be perfectly exposed for the shadow areas.

To understand this, let’s get technical: a scene’s (not a photo’s) contrast ratio is equal to 2 raised to the power of its bit depth. Therefore…

• a sunny day has a contrast ratio of 100,000:1

• an 8-bit JPEG ratio is only 28 or 256:1

• a 16 bit TIFF ratio is 216 or 65,536:1

• a 32 bit HDR ratio is 232 or 4,294,967,296:1!

What Equipment Do I Need to Shoot HDR Photography?

HDR photography is a two-step process. Step 1 is taking the pictures with a series of separate exposures, and step 2 is the processing of these exposures into a single image.

In this article, we will concentrate on the actual shooting of the pictures, and in Part 2 we will focus on the processing of theses pictures.

To take HDR pictures you need:

• a camera that allows you to adjust exposure, preferably one with auto bracketing and that allows you to shoot in RAW

• a tripod, beanbag or other steady support

• a memory card with lots of free storage

• optionally, a remote shutter release

• any lens length that is appropriate for the subject

What Subjects Are Best Suited For HDR Photography?

Our choice of subject should be a truly high contrast scene in which the subject is not moving. Landscapes and still lifes are ideal for HDR photography.

Image on the left of a scene shot in RAW, and the same scene on right after HDR tone-mapping. See how the colors 'pop' more in the HDR image.

Ask yourself--is the lighting even, with no deep areas of shadow nor bright highlights, such that you can capture the contrast in the scene with a single exposure? Or are there too many shadows and bright areas? If the latter is the answer, then HDR is a great choice.

HDR is not for sport or wildlife photos. Since you will be taking multiple exposures of the same scene, a moving target would appear as a blur in your final image.

How Do I Set Up My Camera And Take The Pictures?

All settings are designed so that you eliminate variables over the multiple exposures you will be taking. Your camera should be set on aperture-priority or manual. This is so the depth of field is constant during the exposures. HDR processing produces a lot of noise, so you want to use the lowest ISO available in your camera. Auto focus can change during the multiple exposures, so use manual or single focus lock if your camera has this feature.

• Set your camera’s motor drive to the highest speed burst mode available to cut down on camera movement as you take your pictures.

• Shoot in RAW, if available, to get the highest picture quality you can. This pays off in the processing later on.

• Use auto exposure bracketing (AEB) together with exposure compensation if needed. You need a minimum of +2, 0, and -2 EV (stops) for HDR. Ideally you may want between 5 and 9 exposures. Since many cameras only allow 3 exposures in AEB, you may have to use exposure compensation and take multiple 3 shot bursts to get the results you want.

• Use evaluative or center-weighted metering so that the light is measured across a broad area of the camera sensor to capture the most information possible.

Now that you have all the settings on your camera where they should be, mount the camera on your tripod, plug in your remote shutter release, adjust your aperture for the depth of field you want, focus and start shooting.

In Part 2 we will discuss what to do with the great images you have just taken.  Stay tuned…

Garry Gutterman developed his interest in photography while serving in the U. S. Army, where he would spend hours shooting, developing and printing pictures. After leaving the Army, his interest in photography remained active, but his busy dental practice placed heavy constraints on his time. Upon retirement, Garry again pursued his love of image making with a newfound passion. An early adapter to digital, he switched because it allowed him the true creative freedom that the darkroom never quite did. His main photographic interests are landscape, wildlife, nature and travel photography. His award winning photographs have been seen in numerous exhibits, galleries, and competitions including the Venice Art Center, Ringling College of Art & Design, Visual Arts Center of Punta Gorda, Dancing Crane Gallery, and Art Center Sarasota.

He is a member of the Venice Camera Club, where he has an active leadership role, Dimage and the National Association of Photoshop Professionals.

He may be contacted at: gdgphotography@gmail.com.