Experimenting with Photography
After reading my photography textbook a couple years ago I stumbled upon a photographer that believed the camera and image produced should completely mimic the human eye. Meaning blurred foreground, background and focus solely on the object given the attention. I thought it was brilliant and couldn’t understand why people felt otherwise. Now I’m not saying that his way of thinking is the WAY photos should be shot! Everyone has the right and need to follow their own paths! I just can see where he is coming from. Man built an instrument that cleary was meant to capture a scene as the eye does. But is then lead to believe that foreground MUST be in focus to lead the person in. More visually pleasing? I can’t see how. My eye doesn’t see that way. I mean look at the computer screen before you! Is your hand in focus? The water bottle…or beer on your desk? The blinds or wall behind the computer? Nope! The eye doesn’t see that way. So….beginning today I’m gonna start a little experiment. I’m going to run around town and shoot random images at specific aperatures trying to mimic the eye in full. BLURRED FOREGROUND and all. Street signs, fences, benches, trees, etc. Yeah…living large. Here’s an interesting interpretation of the eye compared to f-stops I found on the net. Check it out…
The retina has a static contrast ratio of around 100:1 (about 6 1/2 f-stops). As soon as the eye moves (saccades) it re-adjusts its exposure both chemically and geometrically by adjusting the iris which regulates the size of the pupil. Initial dark adaptation takes place in approximately four seconds of profound, uninterrupted darkness; full adaptation through adjustments in retinal chemistry (the Purkinje effect) are mostly complete in thirty minutes. Hence, a dynamic contrast ratio of about 1,000,000:1 (about 20 f-stops) is possible. The process is nonlinear and multifaceted, so an interruption by light merely starts the adaptation process over again. Full adaptation is dependent on good blood flow; thus dark adaptation may be hampered by poor circulation, and vasoconstrictors like alcohol or tobacco.
The eye includes a lens not dissimilar to lenses found in optical instruments such as cameras and the same principles can be applied. The pupil of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop. Refraction in the cornea causes the effective aperture (the entrance pupil) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it can range from 2 mm (f/8.3) in a brightly lit place to 8 mm (f/2.1) in the dark. The latter value decreases slowly with age, older people’s eyes sometimes dilate to not more than 5-6mm.