As a photographer, how often have you looked at an image after downloading it from the camera (or even develop it) and wondered why it doesn't look the same as the image you took?
All photographs are unrealistic representations of a reality that we as individuals see. There is no such thing as a photo that is 100% true to what any one individual would've seen.
For a start, the human eye doesn't "see" in the split second (1/60th, 1/125th, etc) that is frozen when the camera sensor is exposed to light.
But more important is the fact our eyes can see way more tones of light - from pitch back to bright white - than a camera can. Therefore where we might see glorious detail in shadows, a camera will often see pitch black.
A relatively new technique in photography is known as high dynamic range or HDR. Used properly, this technique allows the photographer to create an image that has more realistic tones, and which better represents the colours of the real world.
HDR has established itself as a valid technique in landscape photography, and is making inroads into underwater photography. Personally, I am playing with both areas, and am already finding good results with topside stuff, with more work to do underwater.
Like many artistic techniques, HDR can be used to bring realistic colours and tones out, or it can be used to create unrealistic (but nonetheless artistic) images.
Consider the following versions of one of my favourite images - Layabout - which I originally made in 2005 with a Nikon D100 SLR. Given the low dynamic range of this camera, the original image (Layabout, right) is nice, but a bit flat and dull.
With an image like this, basic colour correction in a photo editing program (I use Aperture and Photoshop) will bring more colours out, but there is work to do. Note also the dark shadows behind the boat.
Some photographers would argue that this is a realistic image, but I would argue that its not. The camera simply does not see as many levels of exposure (f-stops) as our eyes do. As we look around a scene in front of us, our eyes constantly adjust, seeing detail everywhere. A camera sees only the exposure of the entire scene at once. Correctly exposing for the most important part of the scene will often mean some detail is lost in the shadows, and some in the highlights.
The second image (Layabout in HDR, left) has been tonemapped using HDR techniques. With my workflow, the image started in Aperture and was then tonemapped in PhotoMatix. The colours and tones are far more realistic, and are much closer to the photographic vision that I had when originally making the image.
More detail is brought out, and the colours seem now to have more "pop". Essentially, the HDR software looks at a three (or more) exposures of the same scene, and then picks the most appropriate exposure from the three images, pixel-by-pixel, and maps those together. The photograph can alter the HDR effect by the use a sliders that tell the software how to apply various levels of HDR strength, saturation, luminosity, and more, as well as determining white point, black point and gamma settings.
An HDR image is typically created by using three images of the same scene, shot at different exposures (typically 0, +2 and -2 EV). Some photographers will use more exposures to get fine detail in a complicated scene.
Another technique is to use a single RAW image. RAW images (NEF files in Nikon, CR2 in Canon, or similar) capture a lot of sensor data, and the HDR software can apply the settings, again pixel-by-pixel, by showing the most appropriate pixel for each image.
The third image (Layabout Reimagined, right) has had far greater manipulation applied in the software than the second. This results in an HDR image that goes beyond realistic, and looks more like a painting than a photograph.
My personal approach is to create representations of the scenes I see, above and below water, in the most realistic way I can. So my personal preference from a photographic point of view is to create images like the second image.
That said, I am kind of blown away by the artistic potential of HDR techniques to create something different. I would not portray this as a realistic photograph. But its fun!
So I believe that for many photographers HDR will be a great way to really show the light of a scene. For some landscape, underwater, cityscape, travel and similar photography it has awesome potential.
I'll be exploring HDR photography more and more. Please follow along with my Photo of the Day Gallery, where I will include regular HDR images from my portfolio. I'll also be shooting with HDR as an end in mind, and trying to create new stuff that uses this wonderful technique.