Nov 14, 2009

How WE See!

Take a Good Look!
I read a provocative article at dpBestflow. In a subsection dealing with HDR, dpBestflow touched on how our eyes see in one of the simplest explanations I've found. Immediately, something clicked; I understood why I like subtle tone mapping instead of some slightly more garish responses created by Photomatix.
In simple terms, nonlinear local adaptation will 'smooth' colors you see. As an example, compare your working 60 W bulb with Magic Hour sunset out the window. Everyone's brain is uniquely filtering what they see to their visual appreciation mode - inside and outside light turns out to be white. WOW!!!
Here's a pictorial definition:
On the left, Photomatix’ Detail Enhancer (Pde) pushed beyond limits my psyche can endure. On the right, added range of light and color from a ‘typical’ 5EV HDR (5EV).

Photomatix, Detail Enhancer, 5AEB, HDR

For my brain, added color Tone Compressed (default) HDR appeals more. When carefully tone mapped in Lightroom and Photoshop - each picture is rich, textured, and lustrous.
But, my brain balks when it sees images where Detail Enhancer, following someone else's visual appreciation, takes me from 'real world' to 'off-world sci-fi'!

How Do Judges React During Competitions?
I’ve spent 4 years watching judges evaluate digital images in competition. The majority will opt for careful tone mapping – voting their opinion through high scores and ribbons. Conversely, lower scores and no ribbons typify more brassy HDR tone mapping conditions.

Here are key vision points from dpBestflow on vision...

In human vision, adaptation is our ability to adjust to dramatically different lighting conditions. Our brains can adjust so we are able to see clearly on the brightest summer day and in a candlelit room. It’s a much more complicated, unconscious, and organic version of ISO.

Local Adaptation
Local adaptation is our ability to adjust different areas of our field of vision to accommodate different levels of brightness, different color temperatures, color casts, etc,. Think of sitting at your desk and looking out a window at Magic Hour. You probably have a 60w incandescent (orange) light bulb over your desk. Late-evening daylight out the window is much brighter and much, much bluer. You aren’t aware of it, but there might be as many as 12 EVs difference between light at your keyboard and light outside, both of which your brain perceives as white light.

Nonlinear Response
Nonlinear response is our ability to accommodate drastic changes in sensory input without overloading our brains. In terms of light, this means - if you double brightness, it doesn’t double your perception. Bright highlights or light sources might be 5,000-10,000 times brighter than their surroundings, but our excellent brains compress that to fit within our ability to perceive.

dpBestflow is a joint venture between Library of Congress and American Society of Media Photographers. Their byline is "dpBestflow is the new guide for every aspect of digital imaging technology from ASMP, the leader in education for the professional photographer."
You might want to take a look at what they have to offer...

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