Monday, November 28, 2011

Photographic Purity– (Beyond B&W: Color)

Black and White photography transitioned to color imaging before most people alive today can personally remember. Bill Watterson, in his Calvin and Hobbes creation (probably the high-water mark of daily cartoon strips), probed this technological shift with an amusing and thought-provoking perspective. Out of respect for Watterson's copyrights I won't provide a direct link here to this particular strip, but you can find it out there if you search for it.

When the ability to capture "true color" images arrived, this new tool was widely seen as nearly miraculous and bringing the viewer ever closer to a "true" recreation of the original scene. This shift from B/W to color was almost (but not quite) as profound as the shift from painted images to photographs had been most of a century earlier. Instead of recording only values (light/dark), this new capacity could acquire the various hues and saturation levels in a scene as well. For nearly the first century of photography, paintings always had the upper hand when it came to coloration– photographs just could not compete in this arena. Now, with color added to the mix, the sky was nearly the limit. In fact, the sky no longer had to suffer the dreary limit of endless stretches of gloomy gray, but could now burst forth with the beauty of its truly blue self.

EARTH AND WATER INTERWOVEN, I, © Bill Brockmeier, all rights reserved
Of course this ability to record the colors apparent in a scene has to be closer to the reality of the original...or does it? It would be instructive here to ask a simple question: "What is color, anyway?" It might come as a surprise to find out that color is not actually a physical parameter, but, in fact, is simply a human perception, a construct of the mind.

While one might say that color is just a matter of the wavelength of the light, this is stripping down the truth of color far too simplistically. There are actual, perceivable colors that don't even exist on the complete spectrum of "all the wavelengths" that are spread out from white light as it passes through a prism. And any specific, perceivable color can actually be created from an infinite number of possible combinations of different other colors. Even more amazing, it is possible for there to be two things that appear exactly the same color under one lighting condition, and yet appear to be dramatically different in color from each other in a different lighting condition (metamerism).

Here is a short list of conditions that can substantially affect the perceived color of an object:
  • color of the light illuminating the object
  • brightness of the illumination
  • color of the object's environment/surroundings
  • colors and intensity of light viewed previous to viewing the object
  • color characteristics of any transmitting medium between the object and viewer

Most probably know that it is in the retina, the light sensitive back surface of the eye, that color is initiated when photons are preferentially absorbed by the different cone (color) receptors. While this is true, this is only the beginning (the barest beginning) of color perception. This is no simple RGB (red/green/blue) modeling of the light that is intercepted, as in a camera. The neural network of the retina takes this simple color "information" and already begins massaging it and reacting to it, before it sends it on to various locations in the brain, which further process these signals into a whole host of responses and outputs, gaining even emotional and visceral components along the way.

While the truth of color perception is highly complex and cannot be quantified unambiguously, what about the "simple" RGB (trichromatic) model used by photography? It turns out that even if we restrict ourselves to discussing this stripped-down technological version of "colors" it is a complex issue. First, there is the camera that takes the complex mix of light and turns it into an array of values that represent the "original colors." Of course, these values are necessarily compared to some "reference white" (would that be an incandescent lamp? a fluorescent lamp? or maybe natural sunlight...and at what time of day?).

The numerical values that are produced by this method are also limited in various ways. First, there is the sensitivity/detection function of the three separate color channels of the camera (basically, the filter transmission curves of the camera's detectors). Then, there is the dynamic range of the values (lightest to darkest) and the size of the steps from one value to the very next. There is also the issue of color gamut– how much of the totally perceivable color "real estate" can be covered by these numerical representations?

Finally, when these numerical values representing the colors in an image have been determined, how will the image be reproduced so it can be seen? Here, the loop is closed by somehow converting the values back into color representations either emitted by the light of a digital monitor, or by the density of different colored ink droplets on paper media. In both these cases, the representations themselves convolve the dynamic range and color gamut limitations as mentioned previously for the camera. On top of that, there are now even more considerations that effect the final colors– things like color gamma in monitors; and for printed images, dot gain, media brightness and whitepoint, and illumination whitepoint, color rendering index, and brightness. And if that wasn't enough, high-end photographic printers now boast of as many as ten or twelve different ink colors to represent those three original RGB colors. As you can see this is a highly complicated issue, and it is an amazing thing that the whole system works as well as it does.

It's clear that there really is no such thing as photographic "purity" when it comes to color. Attempting the photographic reproduction of the "original colors" of a scene may (or may not) be a worthy goal to strive for, but it is simply not possible today (and really never will be). And that's OK. After all, this is an art, and van Gogh did not mix his colors like Gauguin did.

Sunday, November 13, 2011

Photographic Purity– (B&W vs Color)

In my previous post I mentioned that the basis for photography was producing "an analog of what the original subject 'looked like.'" That thought was a kind of off-the-cuff remark, but thinking about it again, I believe it now even more strongly. It is significant that a photograph is aimed not at simply reproducing a physical duplicate of the original, but, rather, in producing (or re-producing) a human perception ("...looked like"). The photographer may be interested in reproducing/conveying whatever her own human perception was of the subject at the time, or she may be interested in producing a particular and wholly new internal perception in the mind of the photograph's viewer (or both).

I believe this matter sets photography apart as an art, rather than as simply a science. There certainly is a place for photography's use as something closer to a science when it is used more simply as a documentary device. In my own work as an optical engineer, I sometimes use photography to purely document the external surface state of a material sample after it has been exposed to laser radiation. And its use in medical and forensic science to document both simple and complex systems and circumstances is invaluable. Even photo-journalism uses something of this documentary power of photography, but in this case, it is equally used to form a perception in the viewer and persuade.

When photography began, it's aim was an image that was composed of light and dark areas, to represent the light and dark areas that were seen in the original subject. This light/dark nature lacked any reference to the original colors in the subject– it was what we now call B/W ("black and white") photography. In this infancy of photography there was not much thought given to what the original colors might have been. At that time the only pigment available on the photographic artist's pallet was a single, simple stick of charcoal. Colors were not what mattered; only values mattered. These early innovators of photography probably never even imagined that photography would someday capture colors as well as values.

Today, there are very few people alive who can remember a time when there were only B/W photographs. And the days of choosing between an inexpensive B/W television and an expensive color unit are decades in the past. In this day, B/W photography is seen as sort of an avant-garde artistic technique, rather than the primitive progenitor of modern photography. B/W is now seen more often than not for its substantial artistic possibilities rather than as an older and cheaper form of photography. This is a good thing.

EARTH AND WATER, INTERWOVEN I, © Bill Brockmeier, all rights reserved
The considerable benefits that monochrome photography brings to the art are wide in spectrum and deep in subtlety– far too great to exhaust in this short article. However, I must at least mention its unique ability to bring the form and structure of an image's composition into clear focus. In some respect, it can offer also distinct abstract qualities to an image, somewhat distancing the observer from the original scene, and thereby bringing them into a closer interaction with their own (or the photographer's) thoughts, impressions, and emotions about the image.

With only tonal values present in the image, color can no longer distract the viewer from the image's underlying structure. This monochromatic vision is a very foreign way of seeing, and usually only experienced under extremely low light level conditions. Perhaps it is this foreign nature of the experience that helps us to see in more than a simply natural and commonplace way. Geometric interplay between various forms and shapes in the image can become paramount. Light and dark, airiness and weight, levity and gravity sing and dance a duet.

It is strange to think that in limiting our ability to see– by removing all color information– we can see things that may have been invisible before.

Of course the final irony in the whole thing is that B/W photography is not truly monochromatic. The white in a B/W image is what a physicist would refer to as "broadband" or "full spectrum" light. This is light that is composed, not of a single wavelength (color) of light, but, rather, of all wavelengths/colors. And even in the original capture of the image, all colors (not just one) came together to produce the image. Truly, "less is more" and "more is less."

Saturday, November 12, 2011

Photographic Purity– (What is photography?)

As I show my work publicly, a frequent question I am asked is— "Do you digitally 'enhance' your photos, or are they 'straight' shots?" Although I think I know what they are generally asking, the real answer is not quite so simple as they might imagine.

What they probably want to know is whether or not I have intentionally used an image editor (like Adobe's PhotoShop) to "pump up" the photograph's color saturation, or contrast, or sharpness, or whatever. They want to know whether I am a photographic "purist" or not. Although I usually respond that "I try to keep the shot as 'straight' as possible," the answer to this question is still not clear cut. Maybe what we should begin asking is "What really is photography, anyway?"

TIME IS MONEY, OR IS IT AN ANGLE?, © Bill Brockmeier
Photography is the process of using the light energy that is coming from a subject to form some sort of physical image that is an analog of what the original subject "looked like." What I mean by "analog" is using one thing to represent another. For example, an "analog clock" uses the angular motion of the clock's hands to represent an amount of elapsed time. In this case, 30° of movement of the hour hand is used to represent one hour of elapsed time. Of course, that 30° is not the exact same thing as one hour, but it is a useful representation of it, since we can't actually see time.

In a similar way, photography aims to represent a view of an original subject by substituting some other "image" that is a function of, or is dependent on, the subject. The specific details of what this representative is, and how that transformation is made from the subject's light to an analog/photographic image, have varied greatly over the history of photographic technology. During most of this history, however, one particular transformation has been king: that of photosensitive silver salts.

From almost the beginning of photography, this process had as its goal the production of an "image" composed of analogous dark areas (due to microscopic particles of silver) that resulted from similar dark areas in the original subject (assuming a positive image). <<<The complexities of that process are far too deep to expound upon here.>>> And, conversely, the lighter areas in the image (resulting from light areas in the subject) were simply due to a lesser concentration of these silver grains, with the lighter substrate showing through to a greater degree. Images produced in this way were eminently recognizable as having a correspondence with the original subject.

It is important to keep in mind here that this "image" made up of silver particles is not actually reproducing the original subject at all. Although we can recognize a photograph of a railway steam locomotive, it is totally obvious that this photograph is NOT a steam locomotive! <<<see Rene Magritte's The Treachery of Images>>> Not only does the image totally lack the weight and substance of the original, it is only a two dimensional pattern, lacking the critical third dimension. At any angle of observance other than perfectly perpendicular, it quickly becomes obvious that the image is severely limited in realism (we won't approach holography in this discussion of photography).

On top of this, the brightness of each little area in the image cannot even begin to replicate the range of brightness exhibited by the real object. About the best the silver image can do is a ratio of brightness to darkness of about 100, while the eye can see a ratio of something more like 1,000,000, and the real object can have a ratio that is nearly unlimited.

These limitations are immense, nevertheless, the transformation of light energy into tiny silver crystals has been an eminently useful, and immensely successful, analogy. Eastman Kodak's billions of dollars, and probably hundreds of billions of photographs taken by the world's population over more than a century are a strong testimony to that success. And the creation of a whole new art-form, distinct and separate from painting, is credited to this transformation of light energy to a pattern of matter.

Then, we have the issue of light frequency/wavelength, or color, which we'll look at in my next post on Photographic Purity.