f-8 and being there

Trying to capture a scene in any sense is difficult. The ersatz photograph allows us to make a semi-permanent record of appearance, but lacks certain qualities that the eye provides. In my time as a photographer, I've learned to compensate for my equipment. When deciding how to set the camera, I consider the deficiencies of in its sensor, lens and post-processing schema.

The eye is extraordinarily sensitive to light. In certain conditions, the eye can detect the presence of a single photon. Because of the overwhelming amount of visual information being sensed, however, this level of detail is attenuated by the brain. Film and digital sensors attempt to mimic this functionality, but both fall short of the eye's remarkable sensitivity. Because of this disadvantage, professional photographic lenses are usually much larger than the eye, allowing the camera to collect much more of the ambient light. At high sensitivity, which is described in photography by ISO speed, a film emulsion or digital photo-receptor responds to a small duration of light. This increase in sensitivity increases the granularity of a film emulsion and allows random noise to affect the image more significantly in a digital camera. The eye suffers a low-light degradation in image quality, relying on rod cells for contrast and failing to depict a full dynamic range of colour, but the camera's low light ability can be altered by changing its lens. By selecting a lens with a large maximum aperture, I can increase the amount of light entering the camera and thereby increase its noise performance in low light. A very 'fast' lens, that is, one with a large aperture, allows for only a small depth of field. This is a tradeoff for increased dynamic range and a high signal-to-noise ratio.

Where dynamic range is concerned, the eye is vastly superior to the camera, and the digital sensor soundly outperforms film. Although the eye is capable of distinguishing 24 stops of contrast, the brain allows us to adapt to differing dynamic scales and adjust our sensory apparatus to the scene. This is a remarkable ability that cameras can't currently match. My Canon EOS 5D can distinguish only 12 stops. This camera drawback can be mitigated by exposure bracketing - taking pictures of the same scene at different exposures and digitally combining the result. This is called High-dynamic-range (HDR) photography and results in some remarkable images.

Even after taking the photo, a camera works to interpret an image much like the brain. An imaging chip conducts signal processing and control operations to minimize noise and maximize color fidelity. The brain similarly operates to mitigate noise and interpret the output of its photo-receptors. As digital signal processing improves, cameras will be better able to produce faithful images like the eye. The camera's shortcomings are largely due to manufacturing and cost restraints, and I expect to see the interval decrease further in the near future. The eye's machinery has been carefully developed over millions of years, and it represents a true technological marvel.