Apply Photoimaging Techniques

CUVPHI04B Apply photoimaging lighting techniques

Acknowledgement to the teacher

Ibrahim Mehmet 2011

CUVPHI04B Apply photoimaging lighting techniques Completion of this unit should enable you to employ lighting techniques to a range of subjects in different work spaces and to select equipment for different lighting techniques.

Transmission through "Polaroid" plastic (for light), this is used commonly for calculator and laptop displays. Materials that show selective absorption are said to display dichroism. Metal gratings for microwaves. (Note that the grating direction is exactly opposite to the rope gratings in the animation below. For microwaves at least, horizontal gratings transmit VERTICALLY polarized e/m radiation and vice versa.) http://www.launc.tased.edu.au/online/sciences/physics/tutes1.html Week 1 - we learned that light travels in straight lines and that we needed to learn the electromagnetic spectrum Light travels in waves and the wider the frequency is in this diagram is equal to low frequency, whereas the closer together equals high frequency. Red is longer and blue is shorter and frequency is the cycles per second. in our notes it referred to “light is a form of energy. Energy is capable of being transformed from one form to another. If we put another log on the fire, it burns, and gives off heat and light. The chemical energy of burning is being transformed into heat and light. If we turn a light on electrical energy is being transformed into light and that Three examples of energy being transformed from one form to another in photography are: 1.

2.

3.

Latent image formation = Light to chemical or electrical.

Taking a lightmeter reading = Light to electrical.

Digital image capture. = Light to electrical / digital.

The electromagnetic spectrum covers a wide range of wavelengths and photon energies, the thing that separates the components of the EMS is their unique wavelengths

Newton made the discovery that light was compounded of different rays, this was published in 1704, he allowed a small beam of sunlight to pass through a prism and noticed that refraction was slightly different for each of the colours he saw. He noted that instead of the light remaining as a small beam it was broken into different colours and they continued to diverge, he measured the different angles and noticed that red was bent least and violet the most. All of these rays of different colour were in the sunlight from the beginning. All colour and vision research was based on this theories, light could be compound or simple.

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The electromagnetic spectrum includes • visible radiation, more commonly called light, • ultraviolet radiation, • and infrared radiation.

Bands of electromagnetic radiation may be described by wavelength and frequency, (or energy level.)

We learned that "Speed of light is constant in a vacuum, E = mc2" and that light is a form of energy made of particles (photons) and travels in waveform from one point to the next.

Light (photons) - Periodic waves

The most common measurement used by photographers is wavelength.

The highest energy is associated with bands that have short wavelengths and high frequencies.

Oscillation

Direction of vibration

Amplitude

Cycle all the way up

tion - Amplitud DirecWavelength e

Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system

Direction of travel

Frequency is in cycles per second are in hertz, 1 cycle is all the way up and all the way down from zero to zero.

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In a beam of un-polarised light all possible directions of vibration are present.

In a beam of polarised light there is only one direction of vibration present.

Radiant energy travels in straight lines.

If you increase the photons you increase the intensity, too much intensity all the subject become white or blown out.

Wavelength is the distance between any two identical points on a wave, for instance crest to crest or trough to trough. We see different wavelengths of light as different colours.

Amplitude is the height or depth of a wave. We see different amplitudes of light as different intensities or different levels of brightness.

Frequency is the number of cycles per second; think of this as the number of crests or troughs passing by a narrow slit in one second. The unit for frequency is the hertz.

Short wavelengths are associated with high frequencies and high energy- long wavelengths with low frequencies and low energy.

Members of the electro-magnetic spectrum which can affect photographic emulsions are: Cosmic rays used for X-rays - Gamma rays = ultraviolet radiation - Ultraviolet radiation = visible radiation Visible radiation, or light - Near infrared radiation The visible spectrum is that portion of the electromagnetic spectrum which we perceive as light.

For photographic purposes the visible spectrum can be thought of as three wavebands consisting of blue green and red 400 to 500 nm blue

500 to 600 nm green

600 to 700 nm red

The slower the wavelength the higher the number Above 400= U.V. and above 700 = near infrared 1 nanometer = 1 billionth of a metre Orthochromatic film - 350-500 so red light wont affect it. It is good for copy work. A latent image is one which is exposed but not yet developed.

The seven colours of the spectrum, red, orange, yellow, green, blue, indigo and violet

CUVPHI04B Apply photoimaging lighting techniques (UM11)

White light is dispersed by a prism into the colors of the optical spectrum

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EMS Member

Cosmic rays

Wavelength Short

Frequency

Energy

High

High

Low

Low

Gamma rays X-rays Ultraviolet radiation Visible radiation Infrared radiation Microwave Radiation Radio and TV waves

Long

Wavelength, frequency and energy relationships between members of the electromagnetic spectrum.

The sun is behaves as a point source of light. A point source of light radiates energy equally and uniformly in all directions.

The diagram illustrates that light waves are not uni-directional, think of 3D movement!

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Periodic vibrations generate waves (photons travelling) how long it takes to reach peaks and troughs and back to zero point Cycle: Periodic, how long it takes to go up down and back again to zero (green section)

Wavelength

Direction of vibration

Amplitude

Direction of travel

Amplitude: is the height or depth of a wave. We see different amplitudes of light as different intensities or different levels of brightness.

Wavelength is the distance between any two identical points on a wave, for instance crest to crest or trough to trough. We see different wavelengths of light as different colours. Â Dire ction of vibration

Wave le ngth

Amplitude

Dire ction of trave l

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Light energy particles (photons), affect light sensitive materials such as film or triggers an electrical pulse in a digital camera sensor. Increase in photon quantity = increase light intensity. a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force.

Luminous

(brightness and darkness) effects

saturation of

an object

Here is a video on Creating and Lighting a Scene on a Budget http://www.slrlounge.com/lighting-on-a-budget-behind-thescenes-lighting-tutorial

diagrams of how the equipment has been set up and the resultant image

http://cyclamenclose2.blogspot.com/2011/02/assignment-205-photo-imag-

http://www.youtube.com/watch?v=mAwTFLi7Tmo&feature=player_embedded CUVPHI04B Apply photoimaging lighting techniques (UM11)

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Determining where to place your subject in relation to the light source, try this exercise to help you see where the light is falling. Position your subject in the area where you want to photograph them.

Stand as far away from them as you plan to be when you take the picture. Now walk completely around your subject noticing the light from all angles. Once you’ve walked around them once, walk a circle around them again slowly. This time have your subject turn with you so they are facing you the entire time. Look at their face closely and notice the changes in light as they face different directions. Notice how the light touches their features and where the shadows land. Notice how the light catches their eyes in each position. Once you find the best direction for your subject to face, take your pictures.

Read more: http://www.digital-photography-school.com/understanding-natural-light-portrait-photography-a-guide-to-learning-to-see-light#ixzz1WARUOClG

Photography Lighting Tips for Positioning the Lights If you're using a 1 light setup, you can position the light about 6 feet from your subject. The light should be at a 45 degree angle from them and pointing down on them. This light is called the key light and is meant to mimic natural light or sunlight. Positioning the light like this will give you strong shadows on the side of the subject that the light isn't on. In order to minimize these shadows you can use a reflector. Postition the reflector on the other side of your model to bounce the light from the key light on the opposite side of the models face. This won't get rid of the shadow completely but it will make it less harsh.

Read more: http://www.digital-photography-advisor.com/photography-lighting-tips.html#ixzz1WATyDm6m If you have a 2 light setup you can replace the reflector with a fill light. The fill light should be dimmer then the key light. Studio lights usually have a switch on the back that you can use to control the power of a light.

If your light doesn't have that you can contol the brightness of it by putting it farther away from the subject than the key light.

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Diffraction refers to various phenomena which occur when a wave encounters an obstacle. In classical physics, the diffraction phenomenon is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. Similar effects occur when light waves travel through a medium with a varying refractive index . Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves

Defracted f5.6

such as visible light, x-rays and radio waves.

Every photographer wants both maximum resolution and maximum depth of field. unfortunately these two demands can be mutually exclusive. As you stop down the aperture on a lens the light passing through tends to diffract, reducing sharpness, though DOF is increased. The reason for this is that the edges of the diaphragm blades in the lens tend to disperse the light. At larger apertures this diffracted light is only a small percentage of the total amount of light hitting the sensor or film, but as the

Defracted f/45

aperture is stopped down the amount of diffracted light becomes a larger percentage of the total amount of light being recorded. Optical theory says that a perfect lens will

be perfect wide open, and that diffraction will start to take its toll as the lens is stopped down.

A soft box far enough away, becomes a point source of light.

Moving the lights even 50cm requires changes to the stops on the camera. The Inverse Square Law in simple terms say twice the distance receives a Âź of the light. As the fraction gets smaller, it means less light. For the test learn the Rectillinear + Transverse learn the names + their meanings. In photography, a rectilinear lens is a photographic lens that yields images where straight features, such as the walls of buildings, appear with straight lines, as opposed to being curved. In other words, it is a lens with little or no barrel or pincushion distortion.

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Above is a picture of a transverse wave. The amplitude of the wave is measured from the peak (or trough) to the mid-point. Amplitude can be defined as "the maximum displacement from the average position". Amplitude is a measure of how much energy the wave has. The wavelength is the distance between two peaks or the distance between two troughs. Wavelength can be defined as "the distance the wave has traveled during one complete cycle". Wavelength is given the symbol l (Greek lambda, pronounced lam-der), and is measured in metres because it is a distance.

Frequency is defined as "the number of complete cycles (complete waves) in one second". Hertz is the unit of frequency (symbol Hz). 1 Hertz = 1 cycle per second.

The period of a wave is defined as "the time taken for one complete cycle". The period = 1 ÷ frequency.

This can be rearranged to give Frequency = 1 ÷ period. Learn for the test that Wavelength is the colour or colour sensitivity + actual colour.

Learn that Orthochromatic is Blue Green sensitive, but not sensitive to red, + the film speed is 80 Orthochromatic photography refers to a photographic emulsion that is sensitive to only blue and green light, and thus can be processed with a red safelight. The increased blue sensitivity causes blue objects to appear lighter and red ones darker. A cyan lens filter—which removes red light—can be used with standard panchromatic film to produce a similar effect.[1] Orthochromatic films were first produced by Hermann Wilhelm Vogel in 1873 by adding small amounts of certain aniline-based dyes to photographic emulsions.

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The reason why the power of the light diminishes so rapidly is not because it 'runs out of energy' or anything like that, but because it spreads and so a smaller and smaller proportion of the light hits the object.

Here's a little diagram to illustrate the point.

1 x unit

P

A

B

2 x units

Surface B is at twice the distance as surface A is from point source P and receives ¼ the amount of illumination As you can see from the diagram the beam of light fans out quite quickly and the object furthest from the light receives only a small proportion of the light, most of the beam misses the target.

The more the beam is focused the higher proportion of the light will fall on the object. With a theatrical spotlight for instance which has a very narrow beam, much more light will fall on the object.

In photography though we don't tend to use highly focused beams as they produce a very harsh light, too contrasty for our purposes. So the inverse square law, as a rule of thumb, works very well for us.

For the test learn Absorption - Light doesn’t go through the object Transmission – Goes through – e.g. clear glass Reflection – Mirror Modern lens transmit 99.5% of light striking it.

Learn Direct transmission, mixed transmission, and diffuse, which are different from the transmission talked about above.

Learn the red + green balls in the powerpoint notes, which colour absorbs which.

We used the red head light in class,(a) which is about 1000 watts, we also have(b) the blondie which is about 2000 watts.

It was said in class that the closer to the centre of of light source the more erratic it becomes.

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(c)

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