Photography as an illusion.

The digital sensor and the processing software that ultimately turns millions of voltage values of the sensor into an image on the computer screen is mostly linear.

Our eyes however are not. Not only are we sensitive onto fractional changes of brightness rather than absolute values of brightness, or concept of brightness itself is highly subjective as this optical illusion will show.

The two central gray squares are, as you would know, the same shade of gray. Consider a real world example.



What is wrong with this photo? Do you see the white and black areas? I assure you neither are white or black. I manipulated it so that it only has gray tones and never reaching the full brightness [or full blackness] of my computer monitor.

The same thing happens in photos, both b&w and colour.



Doesn't the sun glow in this one? In reality, the sun in the picture is of course no brighter than the white background of this blog. If the brightness of your computer monitor is many times less than the afternoon sun, otherwise all this white background of this blog would have blinded you long before you reached this point. The same is true for the shadows. If you have ever looked at an LCD monitor at night with the lights out, you would see that the monitor glows even when you display a black square. Clearly, the blackest of blacks displayable is much brighter than what is found in the real world.

But when tones of gray come together, our brain is able to process them and generate the illusion of light. It is with this amazing shortcoming of our brains to refuse to accept any information at face value that we are able to perceive light in an image that has less than a hundredth of the dynamic range of a typical sunlit scene. The aim of a photograph is not to capture reality, through the choice of exposure, selective focus, composition and the many other tools available to the photographer, the photographer is making both necessary [due to the above mentioned constraints of the medium] and artistic interpretations of reality. A photograph is merely a two dimensional arrangement of tones that creates illusions of light, space, and for the accomplished photographer, movement and even emotion.