LIGHT and VISION

 

LIGHT
There are two general theories to describe the nature of light.  One sees light as waves of energy, the other sees light as particles of matter.  Both of these viewpoints have been proven to be correct by scientific method, yet the two are incompatible.  Things are either waves or particles, energy or matter.  They cannot be both!  Physicists now call this the wave/particle duality of light.  This is one of the major dilemmas of particle physics today.  For the sake of photography it is more convenient to think about light as particles called photons.

REFLECTIVITY
What do you see?  You do not see things.  At least not directly.  Unless you are looking at a light source, what you do see is the light reflected off the surfaces of things.  Do you remember when they told you in third grade that you don't really see the moon, you see the sunlight being reflected off of it?  Gosh, I really thought I could see the moon.  They really like to destroy your beliefs in third grade don't they!

LUMINANCE
is one important term here.  It is the measure of how much light is being reflected. This is the amplitude of the light, more commonly called the brightness of an object.  The brighter an object appears the greater the number of photons being reflected off its surface.  Your black sweatshirt looks dark because it is absorbing most of the photons that are hitting it.  Conversely, a white shirt is reflecting most of the photons striking it. This is also why dark colored garments will keep you warmer and light colored clothing will keep you cooler.

CHROMINANCE
is the other major aspect of light.  Chrominance is the measure of the frequency of light that is being reflected.  This is more often called the color of an object.  The spread of colors that the human eye can see is called the spectrum of visible light.  Remember when they told you in third grade that white light is not really white, but a combination of all the colors?  White light sure looked white to me.  Your red shirt is reflecting the red end of the spectrum while absorbing most of the other frequencies, whereas your blue shirt is reflecting the blue frequencies and absorbing all the others.

Combining chrominance and luminance gives you light blue versus dark blue and so on.  An object can be reflecting a lot of the blue photons or just a few.  With black and white films luminance is the major factor determining how things will be recorded.  A bright red apple and a bright green pear will look more similar on black and white film than will a bright red apple and a dark red apple.

VISIBLE LIGHT
The spectrum of light that is visible to the human eye is actually only a very small range of the electromagnetic spectrum of energy.  This spectrum ranges from gamma rays to x-rays to ultraviolet light above us to infrared light, heat, radar and finally television and radio waves below.  Our eyes perceive frequencies from about 400 nanometers to 700 nanometers.  A nanometer is one billionth of a meter.  The shortest gamma rays (ultrahigh frequencies) are about 10 nanometers while the longest (low frequency) radio waves are 13 kilometers.  To make a musical analogy, the visible light spectrum is less than one octave of frequencies while human hearing is about ten octaves - from 20 hertz to 20 thousand hertz.  The electromagnetic spectrum is an outrageous 30 octaves.  It is worth noting that there are animals that have seeing and hearing ranges that are considerably different than those of human beings or even musicians.


COLOR THEORY

 

ADDITIVE COLOR
When looking at the world we use Additive Color Theory, where the three primary colors of Red, Green and Blue can be combined in an infinite manner to create all other colors. If three lights are shined on a piece of paper, one red, one green and one blue, where all three lights overlap there will be a white patch. When all three colors are added together, they produce white. Combinations of just two of these lights create the secondary colors in additive theory; Cyan, Magenta and Yellow. Where the green and blue overlap, we see cyan. Where the red and blue overlap, we see magenta. And where red and green overlap, we see yellow.

RGB Screens
A television screen and computer screen work in exactly the same way. They are both made up of small dots of red, green and blue phosphor or liquid crystal. When there is no electricity going to particular dot it appears black. When all three are turned all the way up their combined light is seen as white light.

Digital Camera Sensors
The sensor of a digital camera is similar. It consists of an array of small diodes that are each sensitive to a particular color - red, green or blue. All the sensor does is capture the color. It is up to the small screen on the back of the camera or a computer screen to produce an image from what is captured. And actually the picture on the screen is an illusion, because all you really see is a collection of red, green and blue dots. The brain is what renders the full-color image. “The picture is what is on the paper, the image is what is in your brain”



 

 

SUBTRACTIVE COLOR
When we are looking at printed photographs we are looking at inks or pigments on paper. The inks absorb some of the light that is hitting them and reflect the rest. The reflective light is best described using Subtractive Color Theory, where the primary colors of Cyan, Magenta and Yellow can be combined in an infinite manner to produce most other colors. Where all three inks overlap we see black. Combinations of just two of these ink colors create the secondary colors in additive theory; Red, Green and Blue. Where the magenta and yellow overlap, we see red. Where the yellow and cyan overlap, we see green. And where cyan and magenta overlap, we see blue.

Digital Printing in CMYK
Actually we only see something that is close to black, because inks are not pure enough to produce pure black tones. Black inks are often added to the mix to compensate for this shortcoming. The individual black inks also make printing text muck easier.

Production Consistency
The fact that our capture and processing systems are based in RGB technology and the production of photographic prints in CMYK technology, makes it difficult to get a print to look like what we see on our computer screen. In once case you are looking directly at a light source, and in the other we are viewing light (from various sources) reflecting off of pigment on paper. But we can get things close enough and predictable.

 

COLOR CHANNELS
Color film employs three layers of emulsion to make a photograph. One is sensitive to red light, another to green light and the third to blue light. What is produced initially is three black & white negatives, each of which contains the picture information of a specific range of color.

The red, green and blue pixels on a digital camera sensor capture the intensity of only one part of the spectrum The data from each group of pixels s stored separately in what are called channels. Since all the data does is indicate intensity (or luminance), they appear as a black & white picture. It is not until these three channels are displayed on top of each other, and each is converted to color that a full-spectrum photograph is seen. These channels can be opened and modified individually in Photoshop. The Channel Mixer uses this same information when converting color pictures to black & white.

 

COLOR SPACE
Color Space is the term used to describe the range of color that can be used by either a capture device or an output device. Gamut is the term used to measure the width of the color range. The two most common color spaces are sRGB and AdobeRGB(1998). sRGB has a very limited color range designed to meet the lowest common denominator of inexpensive color monitors and it not advisable for serious work. Photos shot in sRGB will look okay when imported from a camera and will make a reasonable color print but only good enough for a snapshot.

Set you camera to capture in the Adobe(RGB) 1998 color space. This has a wider gamut that is much closer to what a professional archival color printer can produce. This color space may appear flat when the photos are imported and require some tweaking to make a great looking print.  But sRGB will never produce anything that looks as good.

A comparison between sRGB (white), Adobe RGB (yellow), and CMYK (black)

Notice that photo paper has a wider gamut than sRGB but smaller than Adobe RGB. It is better to work with the larger space and then 'map' these colors to the paper that is being used. Digital cameras have a gamut slightly wider gamut than Adobce RGB.

You should also want to double-check that the copy of Photoshop that is being used has its color space set to Adobe RGB (1998). Use the Color Setting control in Bridge to synchronize the color settings for all applications in the Adobe suite. Turn on the 'ask when opening'

 

 

COLOR TEMPERATURE
The color of light can be measured in degrees using the Kelvin scale, in which 0ûK is absolute zero. The scale runs the same as Centigrade. Daylight is 5500ûK and color-balanced tungsten light is 3200ûK. In reality, daylight changes its temperature throughout the day. But Flash is also set to 5500ûK.

open shade : 7,000û - 8,000û K
cloudy or overscast : 6,000û - 7,000û K
flash : 5,500û - 6,000û K
midday sun : 5,400û K
early morning or late day : 3,500û - 4,000û K
studio photoflood bulbs : 3,200û K
household tuungsten bulb : 3,000û - 3,500û K
sunrise, sunset : 2,000û - 3,000û K
candlelight : 1,000û K

 

WHITE BALANCE
Most people run their camera on Auto White Balance. In this case the camera is always trying to guess at what ‘white light’ really is and varies the color balance for each shot. This is inadvisable. When shooting film, the entire roll is the same emulsion and the color will always be consistent, frame by frame. It is highly advisable to set your camera to a particular white balance so all shots of the same subject will be consistent. It is equivalent to selecting your favorite film and shooting with it because you like the color it renders. Yes, it is possible to reset the white balance in Camera Raw, but it is better and easier to get it right in the first place.

Some cameras have an extensive collection of White Balances, including daylight, cloudy, shade, flash, incandescent, fluorescent. Manual White Balance can also beused to alter the color rendition. (more below)

 

RELATIVE COLOR PERCEPTION
Adjacent color can change the appearance of color and its intensity. Joseph Albers wrote a breakthrough book on color entitled “Interaction of Color” in the early 1960’s. It is now available in paperback for about $10.

Both blue squares are the same color.
They appear different because of the surrounding color.

 

RAW FILES
RAW files make it possible to use the numerical data from the capture before it has been manipulated by the camera’s processing engine. This processing makes it possible for non-professionals who do not want to deal with technology to make nice photographs without the work. The fact that you are in this class means that you want more quality and better quality photos. To do this you will have to take control and make decisions. But you can always go back to the Raw files and manipulate how the camera will process the files, if at all. More on how to use this later.

It may be necessary to convert native camera files that use proprietary formats into the DNG format, the generic Digital Negative format created by Adobe for universal access. Converters are usually available for free from the individual camera manufacturers. The TUCC Lab will probably not have all of these specific applications on hand.

 

ISO
The ISO rating also affects the color of the captured color. ISO does not vary the sensitivity of the chip. That is constant. What happens is the signal is amplified to produce more information form less light. This is the source of the noise in photos shot at high ISO. Use the lowest ISO setting you can get away with given the circumstances in which you are shooting. note: some of the newer cameras have made great leaps in reducing noise at higher ISO settings.


 

WORKING COLOR MODES

 

LIMITED COLOR PALETTES

 

NONOCHROME
Neutral color palette can produce photos that look like black & white but have a subtle tinge of color.

 

MONOCHROME
Subjects with a primarily cool or warm color sense…

 

HARMONIOUS COLOR
Color of similar hues work well with less contrasty compositions.

 

COMPLIMENTARY COLOR
Use the color wheel to see what colors are opposites. Simple bold compositions work well.

   

 

TERTIARY COLOR
Colors that are one-third of the way across the color wheel can also make interesting color studies.


COLOR BALANCE to EVOKE a MOOD

 

COLOR SHIFT with CREATIVE WHITE BALANCE
Simply by shifting the white balance from warm to cool while shooting a subject that has a different white balance, interesting shifts in color can be generated. This requires knowledge of the range of color temperatures and the light sources that create them.

cool neutral warm

People have also used a manual white balance on an object that is far from white. The shots came out crazy but nice, and actually not as off as you might think. This is another strategy for creative control.

 

OVER the TOP COLOR
Some subjects can shot more or less as is if their color itself is over the top.

 

 

EXTERIOR AMBIENCE
Particular light with a minimal subject works to create an almost surreal sense.

 

 

INTERIOR AMBIENCE
Capturing the ambient light in an interior space can evoke emotional impact.

 

 

EXTREME TIME OR WEATHER
Sunlight or the lack thereof creates ambience or ‘feel’.

 
fog at 3 AM    sunset walk

 

EXTREME NATURE
Arctic sun and fire in the desert may be hard to find in an unban environment, but…

 

 

ABSTRACT FORM through CLOSE FOCUS and/or SUBDUED COLOR
Eliminating much of the peripheral space and reducing the information in a piece, added to a reduction in color range is an example of ‘Form Supporting Content’.

 

 

RESTRICTED VIEWPOINT / RESTRICTED VISION
Forcing the viewers view combined with restricted color creates interaction between artist and audience.

 

 

REFLECTED LIGHT / LUMINANCE
A key point in dynamic photos is Luminance - making it look like the light is coming from the objects in the print, not just falling on them. A classic tool to achieve luminance in a print is to include reflective surfaces, most notably water.

 

 

COLOR BALANCE changes HOUR by HOUR
The color of the sunlight changes continually with the time of day. The most extreme tonalities are at dawn and dusk. One can shoot at these times, or digitally manipulate the tonality of a photo to mimic these shooting conditions. One can also study the changes in color with the seasons and use these to convey feeling.

 

COLOR SHIFT in NATURE / VARIATIONS on a THEME
Varying the angle of view, or time of day, or even change in season can produce interesting variations in what might othewise appera very similar if not the same.

 

MULTIPLE IMAGING / COLLECTIONS
While these pictures may be too simple to stand on their own, they gain power by being placed in a group.