The WOW! Buzz

I spent some time this past weekend mounting a couple of prints from my trip to my ancestral Montana home last summer for my office at work.  As an avid amateur photographer, I’m always trying new techniques to produce the strongest photographs possible.  One of my favorite techniques that I use quite often is known as HDR (high dynamic range) photography in pro and serious amateur photography circles.  It is a relatively new technique, though not a new idea, made possible by the strong digital processing options available to digital photographers today.

Here’s the thing.  If we are to consider the action of the pupil in the eye adjusting to varying light, the eye has almost 24 f-stops of dynamic range–said another way, we can see a starlit sky in the dead of the arctic night all the way to sun blazing off of a placid lake on the equator at noon-an increase of one f-stop essentially doubling the brightness perceived.  But even at a static pupil aperture, the eye can still detect between 11 and 14 f-stops of dynamic range, and we use the dynamic range of that wonderful instrument daily to see detail that no past or present camera (including film) technology can capture.

The state of the art dynamic range available from the sensors on high end digital cameras or video cameras today is about 8.5 f-stops–material outside of that shows up as either straight black or straight white.  So while an eye can look at a scene and see 11-14 f-stops of dynamic range, a digital camera/video camera will only detect slightly more than 8 f-stops, and because this is a logarithmic scale, this is a significant difference in performance.

The technique I presently use in my digital photography is to bracket three quick exposures, one under exposed, one properly exposed, and the final over exposed.  Both my cameras can be set to do this automatically, and both support “rapid fire” exposures–up to 8 frames per second.  So this can be done quickly as one is shooting the picture(s), but (and here’s the rub) these three negatives must then be combined digitally using computer processing techniques to create a single high dynamic range image.  In other words, almost 64 megabits of data from multiple negatives must be processed to create a single 20 megapixel image in HDR.  The results are stunning–detail that looks realistic to the eye when properly done.  Like anything else, this technique can be taken to the extreme and not all HDR pictures are particularly life-like.

So what does this have to do with my TV?  Most current video displays have the raw ability (if not the actual circuitry) to display dynamic range that simply isn’t available in most video content.  It is possible that the “next big thing” in video will be getting the content, storage, transmission streams, etc. to move to true high fidelity video (not just high definition) by increasing the dynamic range to something closer to what the human eye can perceive.  My sense is that this element may be more important to video cognoscenti than 3D in terms of actually enhancing the video experience.

Next week, I’ll discuss the fine points of this future technology and the ramifications to the industry should it be adopted.  In the meantime, take a look at this sample of HDR video–understand it’s highly compressed and just a rough approximation of what is possible, but very intriguing nonetheless.

HDR video sample

Until next week….

For the past year or a little more, some manufacturers have been producing high end sets which are billed as “LED” sets, or “light emitting diode”.  This has been a confusing distinction because all flat panel TV’s are either plasma technology or LCD (liquid crystal display) technology.  Light Emitting Diodes are those small, expensive Christmas lights, or the little red numerals on an old calculator, right?  So is that what makes the picture on these LED sets?  Millions and millions of little diode lights?

In a word, no.  Every LCD television requires a backlighting system which is on at full brightness all the time.  The millions of LCD semiconductors in a flat panel set act as “light valves” to that backlight, allowing anything from no light (black) to colors of various brightness (256 levels of brightness per color) to being completely “open” (bright white) on the screen (a bit of a simplification, but bear with me).  For most LCD televisions, the “backlight” source is a full color spectrum fluorescent lamp array running at full brightness.

What is different in an “LED” HDTV is that the backlighting system is made up of a large (white light) LED array rather than the fluorescent lamp array found in a more conventional design.  This approach has several advantages:

1) LED backlight requires much less energy to operate at full brightness–less than half the energy in most applications.

2) LED can be designed to provide a much wider spectrum of color in the source light they provide than a fluorescent light.  (Ever notice that a diamond doesn’t sparkle much under a fluorescent office lamp?  Same principle–a TV needs a “broad spectrum” white light to produce a full range of natural colors.)

3) Sets can be made much thinner and lighter vis a vis a conventional backlight technology.  Some LED driven LCD sets are just over an inch thick while most conventional LCD sets run 2.5″ to 4″ in thickness.

4) Unlike a fluorescent display, some designs of LED array can be selectively “brightness controlled” by circuitry especially designed to enhance the picture.  Remember our discussion a few months ago on contrast ratio? The tiny semiconductor “valves” of the LCD have some limitation on how black the blacks can be (with a highly energized white backlight behind them) compared with the bright areas of the picture.  Because an LED array is, in most designs, many small light devices either behind or at the edge of the LCD matrix, selective areas of the picture can be brightened or dimmed to help the LCD matrix do its job.  When properly implemented, this technique results in enhanced contrast ratio, and  in certain ambient light conditions, a visible enhancement to the picture.

These sets are higher end designs, and the price is commensurate with the high end label.  But some of these sets I have auditioned have truly stunning video quality, and bear investigation if you are in the market.

Until next time….