Camera versus Eyes

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Today’s Question: I’ve been told that a digital camera can’t capture as much information as human vision. Is that true?

Tim’s Quick Answer: I would say that a digital camera can actually capture more information than normal human vision is capable of, though perception can be a bit different from this.

More Detail: I most often hear the suggestion that human vision is “better” than a digital camera in the context of high dynamic range (HDR) photography. The suggestion is that by creating an HDR image you are matching the advanced capabilities of human vision. Instead, I would say that HDR photography reproduces the illusion of human vision.

The reason we might perceive human vision as having greater dynamic range and greater depth of field than a digital camera is that our eyes are constantly adjusting in terms of exposure and focal point as we move our view around a scene.

A classic example of the limitations of human vision is illustrated by walking out of a dark movie theater into daylight. It takes a minute or two for our eyes to adjust from a dark environment to a very bright environment, which illustrates that the dynamic range of our vision isn’t really all that significant. Rather, as we move our eyes around a scene with varying light levels, our pupils adjust to effectively alter the exposure of our vision.

Similarly, as we move our eyes around a scene, our focal point changes rapidly, providing the illusion of tremendous depth of field. We actually see a very small area of a scene to be in perfect focus, both in terms of depth and field of view.

So, in general I would say that a digital camera is actually able to capture more information in terms of dynamic range and depth of field, when compared to normal human vision. The difference is that human vision is simply making constant adjustments, while a digital photo preserves a single (hopefully decisive) moment in time.