Chris Zammit30 January 2008, 6:17 AM
Pentax's latest digital SLR cameras have a new High Dynamic Range system built in that lets you take stunning photos like this one without extensive Photoshopping.
 HDR magic: this stunning pic was created from multiple exposures. (credit: Peter Van Allen -- click the pic to go to his Flickr page) |
Ever wondered how some photographers can take a shot with amazing detail and colour even in the darkest and brightest areas?
It's a technique called High Dynamic Range (or HDR), where multiple exposures of the same scene are captured (allowing the dark areas to be photographed brighter, and very bright areas to be photographed darker in various exposures.)
Then, the photographer melds the photos together in Photoshop, taking the best parts of each exposure. With some careful soft-edged-brush work, you can create a composite photo that looks amazing.
 HDR eye: credit - Salento Gilby. Click the photo to go to his Flickr page. |
The problem until now has been that it's very time consuming to merge the shots together, making HDR more of an artform than a practical every-day photography tool.
That may be all about to change, with Pentax announcing the launch of two new digital SLR cameras with built in HDR capability.
What until recently was a multi-step process, which required taking multiple exposures, combining them in specialised software, and then tone mapping the final image, can now be performed in-camera.
 Pentax K20: HDR built in, but when can we get one in Australia? |
The Pentax K20D and the Pentax K200D both use a new metering system which allows their CMOS sensors to take simultaneous readings of both highlight and shadow areas.
The user then simply needs to access the camera's HDR mode through the menu dial, set the camera up for the first shot, press the shutter, and off it goes. The internal sensors will then take three shots and combine them into a single HDR image.
 PRA airlines: a plane held at Aviation Warehouse in California, used in an Indiana Jones movie and photographed here in beautiful HDR. Credit: Lost America (click photo to see his Flickr page.) |
How it works
Firstly, the standard correct exposure photograph is metered and exposed. The onboard sensors then independently calculate an overexposed image and an underexposed image.
Within seconds, the K20D and the K200D will have taken three separate photographs and will begin the process of merging them into a single HDR image. Control is limited as the only control the user has over the process is to decide whether the camera will expose the over and underexposed images at one or two stops above or below correct exposure.
Once all three photos are taken, the contrasting areas of the images are compared, balanced and combined into a single picture which displays a broader dynamic range than a conventional photograph, allowing for more evenly exposed images and a more natural look. With LiveView, the results can be instantly previewed, and the process repeated if necessary.
BE WARNED: Pentax's HDR capability is still strictly limited to still life or scenery photography only. If your subject is moving, it won’t work (unless you get everybody to stand really still).
However, with the introduction of HDR in mid-range DSLR cameras, we can say goodbye to the days of overexposed backgrounds or foregrounds in shadow.
Although these ‘automated’ results are not as dramatic as those obtained using more traditional methods (see below) the quality of the images is still impressive.
The 14.6 megapixel Pentax K20D will cost $1999 in Australia with 18-55mm lens, and its little brother, the 10.6 megapixel K200D, will cost $1199 with the same lens. The only bummer is that Pentax Australia does not yet have a confirmed release date, other than "in the next few months".
Understanding HDR
High Dynamic Range Images are a relatively new trend in photography which enables the reproduction of a wider range of light intensity levels than is possible using normal photographic methods.
The human eye works in much the same way as a camera. Both are unable to accurately view dramatically different variations in light at the same time. Although we can see over a large dynamic range (humans can see in both dim lighting and in bright sunlight), our eyes can’t do both simultaneously. There is simply too much information to be decoded over such a huge dynamic range to make this possible.
In bright conditions, we see shadows as looking black and impenetrable. They look solid with no visible details. The same is true for bright lights viewed in dim conditions. Our eyes (or the camera) adjust to the darkness around us causing any bright areas to flare out and appear as a solid blank area of white. In essence, under bright conditions, shadow detail is lost. In dim lighting, details within highlights are lost.
However, digital cameras do have a dramatically reduced dynamic range than the human eye, which is why what looks like a beautiful landscape to your eye may end up having exaggerated areas of darkness or blown-out areas of brightness in a digital photo.
With the invention of HDR (High Dynamic Range) photographic techniques, photographers have found a way to capture the data from a wider dynamic range than is naturally visible to create vibrant images that were previously unrealised in photography.
The concept is pretty straightforward and involves taking a series of photos of the same scene at differing exposures (or areas along the dynamic range) and combining them to create a single image.
On a simple level, a photographer can take a minimum of three images of an object, exposing for different light levels. In one image, they may expose for the highlights of the scene to capture as much detail as possible in the bright areas of the image.
Next, another image is taken with the mid range lighting exposed for.
Lastly, another exposure set to capture the shadow details will be taken.
These three images will then be combined in Photoshop to produce a photograph that shows the details and correct exposures for the highlights, shadows and everything in between. Only the most accurately exposed areas of each image will be used. Wherever the most detail lies, that is typically the area that will be kept.
 Blended images: this example, from HDRSoft, makers of the HDR software Photomatix, shows how multiple exposures can be brought together to create an HDR picture. |
The more images taken for each photograph, the better the dynamic range will be. Many photographers take around seven photographs for each image created. For the maximum effect, some photographers may take an image for every two stops on their camera to provide the maximum coverage of the dynamic range.
Once combined, tone mapping is used to compress the dynamic range of the image to within the visual range of the viewer or reproductive medium without compromising image details or quality.
After that process, the information from a wide dynamic range of light conditions is now visible within the narrower dynamic range that we can see at one time.
Every part of the image is now displayed at the correct exposure with a maximum of detail. Colours look richer as they are no longer muted by being under or over exposed. Through HDR images we can now look at the world in a new way, a way in which our eyes aren’t naturally accustomed.