High dynamic range or HDR photography extends the number of luminance values in a photograph. What this means in layman’s terms is that dark parts of an image still have detail and don’t turn into a black blob of ink and bright parts of an image don’t blast to white. This is essential for 3D multiperspective photography because the most compelling photographs present to the eyes in the same way real life is presented to the eyes. Our eyes adapt instantly to changing light conditions and we see an amazing tonal range that extends far beyond a regular photograph with standard dynamic range. We see many subtle shades of darkness and white sand in the bright sun still has sand grain detail that is easily visible although we might have to squint. The dynamic range of our eyes greatly exceed the capability of cameras – both film and digital.
Take a look at this photograph as an example. Note on the right side standard dynamic range photo how the black fabric turns to black and the hair ribbon blasts to white. A considerable amount of detail is lost making it difficult and even impossible for some parts of the image to have clearly defined perspectives. (See blue circle blow up for detail)
One might argue that it is better for flat single perspective photographs as well. And for some that is true, however, often times a photographer wants to simplify the photograph or add dramatic lighting and these subtle changes in luminance (brightness) are less important. Also, with a flat photograph more detail in the background can conflict with the main area of interest in the photograph. Without dimensional depth to set it out, too much detail can be undesirable for a flat single perspective photo. With the example shown here one could argue that the detail of the black fabric takes away slightly from the baby. But in 3D there is a world of difference that has to be seen to be appreciated. That extra dynamic range provides the detail in 3D to clearly position the baby in it’s space and the stereovision perception is greatly enhanced. It looks far more realistic.
So, how do you get more dynamic range out of a camera? In my case, I have imaging sensors and special processing that extend the image data captured to 18 bits per color (red, green and blue)**. A regular camera with jpeg output is limited to 8 bits per color. Those extra bits I am able to obtain with my custom rig contain subtle changes in luminance levels that can be processed and printed to appear similar to the way the eyes would see them in real life.
Another way (actually the way most people do it) to make an HDR photograph is to take 3 or more photographs in quick succession with a bracketing camera option where the shutter speed is different for each photograph. Then using special HDR software they combine the different exposures into a single photograph with a broad tonal range. Sometimes the effects of this processing is very effective. For example, room interiors with windows look much more natural. Like anything though, it can be overdone and create very unnatural looking images. A big problem with this approach is that you are limited to shots that have no movement during the multiple exposures. In order for me to take action shots, I had to create a system that captures all of the data at once, at shutter speeds in the hundreths of a second range.
** A regular Canon Camera RAW image has 16 bits per color. I do use Canon sensors but I have been able to tweek things to get an extra couple of bits per color at the expense of error correction, which I must perform in a separate process with a computer. It will remain a secret how I do it, unless and until I am able to obtain a patent for the process. If you really have sharp eyes, you might also be able to detect that I’ve reduced color fringing and ringing around sharp luminance transitions. That’s another benefit to extra bits.
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