0.2 grams

2.0 grams for 30ft

Bulbs could only be used once

The could explode if the vacuum seal was damaged

They were as large as a household bulb

• term “strobe”

• term “speedlight”

• invented “shutterless” camera

• “The man who made time stand still” National Geographic

• photographed things we could not see

• “Papa Flash” Jacques Cousteau •

“Doc” Edgerton

The duration of the flash can be controlled accurately

High intensity of light

Can be powered by batteries, batteries in the camera, or a separate power pack

Life expectancy is very long. Can be fired 1000's of times

The burst of light is much faster than a bulb. It can stop motion

1.“Pop-up”

2.“Hot Shoe”

3. External

4. Studio

5. Self Contained

• fast, easy, small

• limited power

• not adjustable (tilt, zoom)

• “deer in the headlight” look

• doesn’t work well vertically

• good to add some “snap” on a cloudy day

• more power

• larger light source

• adjustable (tilt, bounce, soften, wide)

• external power

• PC sync

• wireless camera connection

• even more power

• larger light source

• adjustable (tilt, bounce, soften, wide)

• external power (more flashes)

• Quick recharge

• less sophisticated 

What are the characteristics of self-contained flash heads?

(Monolights)

• “studio” light (not portable)

• AC power with power pack built into head

• adjustable size with reflectors

• Powerful

• location kit

• power measured in watts 

•Typically very powerful, power pack can power and control more than one head.

•Flash head has no power source so it must plug into the power pack

•Power pack plugs into wall outlet

Manually

Automatically 

and Dedicated, TTL (Through the lens)

Simply fires when it receives a signal. Not syncable with your camera, either the camera or subject must move closer. Or adjust aperture

Flash fires, sends out a beam that measures the light on the subject and if necessary it will kill the flash before full discharge

Often produces overexposed images

There are extra pins on the bottom of the hot shoe that talks to the camera.

The camera feeds the flash information on how much light, when to fire and for how long.

Measures the ambient light as well as the light reflecting off a subject.

The flash can help the camera to focus because of the infrared beam.

The camera can tell the flash which lens is being used.

Then the flash can zoom on it’s own to match the zoom of the lens.

It directs the beam of the flash.

More even and accurate exposure

The flash helps the camera focus

The camera tells the flash what lens it is using

The camera tells the flash how much light is needed

The camera can measure flash and ambient

Hot-shoe

•Most cameras have a hot shoe that fits the “foot” of a flash

•This connection is required for the flash to know that the shutter had been released and the flash needs to fire

•For dedicated flashes, this is where the camera-to-flash communication will take place

The hot shoe communicates electronically with the flash and camera

The cold shoe only holds the flash. There is no electronic communications

The flash travelling through the lens and it hits the retina at the back of the eye and reflects back

By using red eye reduction mode

By removing the flash from the camera and holding it higher

Very bright AF-assist light fires before the main flash exposure

Flash fires repeatedly before exposure

Used if the flash does not mount to a hot shoe

•Also used when positioning a non-TTL flash away from the camera

•This cord connects to the PC terminal on the camera and the flash

•Some cameras do not have PC terminal, so they require a hot shoe adapter.

The adapter has a PC terminal built-in and it fits on the hot shoe so that the flashes sync cable can now connect to the camera

It has curtains 

 has 2 curtains ... one follows the other and at fast shutter speeds it is never fully open

[image]

A leaf shutter has “leaves” instead of curtains

Can be fully open at all its shutter speeds, therefore it does not have a sync speed.

It syncs at all speeds.

[image]

Loop lighting is probably one of the most common key lighting patterns.

Loop Light is a nice middle ground where most of the face is still in light but you still have enough shadows to bring in some definition.

The main or key light is primary and usually strongest.[image]

Fill light provides light to help fill in areas with lots of shadows.

The light should be even and non-directinal that adds little character or shadow of it's own.

It is almost always weaker than the main light.

[image]

They are also known as rim lights

They are usually low and behind or to the side of the subject

[image]

Similar placement a kicker but above the the subject instead of below.

Adds highlights to hair and separation fro the background

Shouldn't be used on thinning hair or bald heads

[image]

It is used to illuminate the background. 

Separates the subject from the background

[image]

Butterfly Lighting (or Paramount Lighting) comes directly in front and above the subject’s face.

This creates shadows that are directly below the subject’s facial features.

The most notable shadow, and where this lighting pattern gets its name, is a butterfly shaped shadow just under the nose.

It is also called “Paramount Lighting” because this lighting pattern was used heavily in the Paramount movie studio of old Hollywood.

[image]

Rembrandt lighting can be distinguished by half of the subject’s face in shadow except for triangle-shaped light on the cheekbone and eye.

Named after the Dutch painter, Rembrandt, who painted in this style.

Best used in moody or character work[image]

Split lighting simply “splits” the subject’s face, lighting half of your subject’s face while leaving the other half in shadow. 

Light is placed to the side about 90-120 degrees

[image]

When lighting is illuminating the side of the head away from or not visible to the camera.

The most commonly used position

Great for narrowing a face

[image]

The light illuminates the subject on the same side as the camera is positioned.

Useful in casting a Rembrandt shadow

Makes a face appear fuller

Not always flattering and not as common as short lighting

[image]

When the light source, camera an subject are all along the same lateral axis

Illuminates the front of the face and the sides to some extent

Can create the butterfly shadow

[image]

GN = DxF

GN is a product of the lens aperture (F) and the flash-to-subject distance (D) required for a correct exposure 

F=GN÷D

f-stop (aperture) = Guide Number ÷ distance

This is the aperture calculation if the distance is 10ft and the Guide Number is 80...

f# = GN ÷ distance

 f# = 80 ÷ 10

 f# = 8

therefore, the aperture is f/8 when the subject is 10ft away.

What would the result be if the distance is 15ft?

f# = GN / distance

 f# = 80 / 15

 f# = 5.333

the aperture would be f/5.6 when the subject is 15ft away

(round to the nearest aperture)

 f# = GN / distance

 f# = 80 / 5

 f# = 16

the aperture would be f/16 when the subject is 5ft away

F = GN / D

F = 18 / 2

F = 9

the aperture would be F8

How do you find out the Guide Number of a flash?

For example your aperture is f/8 and your FLASH TO SUBJECT distance is 10ft..

GN = D x F

GN = 10 x 8

GN = 80

GN = F x D

GN = 11 x 10

GN = 110

1. Reflectors

2. Zoom Heads

3. Units (meters or feet)

4. ISO

If the distance is calculated by feet rather than meters it will have an effect on the GN.

The Canon 550EX has a GN of 55 when the flash is zoomed for 105mm coverage ... in METERS

 The Nikon SB 800 has a GN of 184 when the flash is zoomed for 105mm coverage ... in FEET

No.

The GN is ISO specific. 

If you change your ISO your GN will also change.

It is affected using the Inverse Square Law.

Instead of doubling or halving, it is 1.4 times.

Similar to apertures being 1.4 times between stops

    ISO             GN

     50              40

   100              56

   200              80

   400            110

   800            160

      1600            220     

        3200            320       

When the ISO is doubled the GN increased by 1.4 just like apertures. If the GN is changed then the ISO is doubled or halved to match.

If your GN started at 110 then was REDUCED 1 stop to 80

and your ISO remains the same, 100, then your aperture must increase 1 stop to maintain exposure.

Therefore 

GN 110 = ISO 100, f/16, @1/125 

is the same as 

GN 80 = ISO 100, f11, @1/125

Flashes that use external packs.

Monolights (all in ones)

Most flashes that typically are not hot shoe flashes

If you double or halve the watt/second you change the f/stop one full stop

(similar to ISO - halving or doubling the ISO also changes the f/stop one full stop)

Reflectors

Flash Tubes

Umbrellas

Softboxes

Imagine that you have an Elinchrom Ranger portable strobe system, set to 100 w/s.

You currently have your camera set to f/8 @ 1/200, ISO 200.

 What is your new aperture if you set your flash to 200 w/s?

Front curtain sync - the flash fires as soon as the shutter opens or first curtain opens.

Rear curtain sync - the flash fires just before the shutter closes or rear curtain closes.

[image]

All the light is striking the subject from one position, or hitting it at the same angle

produce hard edged, well defined shadows

These can include bare light bulb mounted in the ceiling (no diffuser), spot light, camera flash

However, these lights are assumed to be a fair distance out from subject.

At a far distance, yes, the shadows will be hard edged for example the sun. 

It is far away but produces hard, well defined shadows 

Light from a large light source strike their subject from many different angles, produce soft edged, less defined shadows

These can include light bouncing off a wall or ceiling, large softbox or umbrella, light from a northfacing window. However, this also assumes that the large light source is reasonably close to the subject.

ie. Moving a softbox to an opposite side of a gymnasium, will make it act like a small light source

 Aiming the light so that the subject is lit by the “Penumbra” of the light while the “Umbra” is aimed beyond the subject.

[image]

Either of the edges.

The center of the softbox has the harshest or brightest light.

[image]

Shape

Separation

Depth

Texture

Front lighting is flat or 2D

Light from the side or back will reveal shapes

It makes the main subject stand out from the background

when you use a background light

When you make the background darker or lighter if creates demension or 3D

There is a foreground, midground and background

Lighting from the front or near the camera will obscure texture.

Lighting from the sides creates shadows and texture comes from shadows

Purpose of Light     Portrait Lighting

1.Shape                 1.Main Light

2.Separation           2.Fill Light  

             3.Depth                 3.Background Light  

   4.Texture                4.Accent Light

Main

Key

Form

Create the shadows that will reveal the shape of the face The name, “Form” light comes from the fact that it reveals the form of the subject

Usually it also illuminates both eyes

Split, Rembrandt, Loop and Butterfly

[image]

Broad and Short Lighting

[image]

there is one side that we see more of

tends to widen the face (so good for thin faces)

lit from the side closest to the photographer

there is one side that we see less of

Short tend to thin the face (so good for round faces)

lit on the side furthest from the photographer

Variation of Short Lighting

a triangle is formed by the shadow of the nose touching the shadow on the dark side of the face

Main light is directly in front of the face and high

Creates a symmetrical shadow under the nose

Caution: If main light is too high, the shadow will touch the lip and create dark eye sockets

Hides texture

Reduce shadows, hides flaws, wrinkles etc

Center lighting

Beauty lighting

Skylight lighting

High frontal lighting

Lasky lighting

Paramount lighting

Marlene Dietrich light

Symmetrical light

Usually it should be high enough that the shadow from the nose is cast downward

Approximately 45 degree angle downward toward the face

Illuminate the eyes (tilt of the head)

Main light is moved so far to one side or the other, that only one side of the face is illuminated

Opposite side is in shadow.

The face is split in half by the light

This can occur in both broad and short light set-ups

Reduces contrast

Fills shadows created by the main

Should not create shadows of it’s own

Behind or near the camera (reflector)

Provides separation

Adds the illusion of depth

Gives shape to the subject

A light that comes from behind and higher than the subject

Rakes across the hair

Usually a spot light, but not always

Adds sheen to the hair

Shows the texture

Helps with separation

A light that comes from behind the subject

Adds an edge of highlight along clothes, face, shoulder, arms etc.

Reveals some texture

Also helps with separation

Adds mood to a portrait

The catch lights created by the fill lights are usually removed in Photoshop.

The catch lights created by the Main light stays

1:1, 2:1, 3:1, 5:1, 9:1

The higher the ratio, the greater the contrast 

1 unit of light hitting the subject directly

or

1 unit of equal light on both sides of the subject 

A 1:1 ratio is even lighting, it has no ratio, and there is no difference in meter reading from one side of the face to the other.

This is very flat lighting  

[image]

The light on one side is twice as powerful as the other

No difference between Main and Fill lights, but… now one side of the face brighter than the other

2 units strike the one side compared to 1 unit striking the other side

[image]

There is now 3 units of light on one side of the face and only 1 on the other

There is one stop difference between the main and fill light

Therefore the fill equals one unit of light and the main equals 2 units of light as it is 1 stop different than the fill.

[image]

When there is a 2 stop difference between the main light and the fill light the ratio is 5:1

I.E.

Main light f/8 fill light f/4...there is a 2 stop difference between the fill and the main so...

f/4 to f/5.6 = 1 stop or 2 units of light

then f/5.6 to f/8 = 2 stops or 4 units of light

Each units of light are doubled so 1 stop = 2 units

2 stops = 2 units x 2 or 4 units 

Then we add those 4 units to the 1 unit created by the main light for a ratio of 5:1

This is based on a 3 stop difference between the main and the fill lights.

The main light is f/8 and the fill light is f/2.8 

so....

f/2.8 to f/4 = 2 units of light

f/4 to f/5.6 = 4 units of light ([f/2.8 to f/4] 2 x [f/4 to f/5.6] 2 = 4)

f/5.6 to f/8 = 8 units of light ([f/2.8 to f/4] 2 x [f/4 to f/5.6] 2 x [f/5.6 to f/8] 2 = [f/2.8 to f/8] 8)

So then we have 8 units of light on one side plus the 1 unit from the fill to make a 9:1 ratio

Used when wide apertures are required in brightly lit outdoor settings

Portraiture

Fashion

Sports photography 

When light strikes a surface (usually metal), some electrons are ejected which can produce a charge and in turn produce a current.

Energy from the light is absorbed by the electrons in the metal which gives them enough energy to be emitted or knocked out of the metal.

1969

George Smith and Willard Boyle

It was used in 1974 to produce the first astronomical photo ever taken by a digital camera.

It consisted of an image of the Moon captured using a 20-centimetre telescope.

In December 1975

It was black and white

by Kodak engineer Steven Sasson

A silicon semiconductor that is composed of an array of photosensitive diodes (photodiodes) called photosites.

In other words it is essentially a grid of photodiodes.

These “photosites” receive photons (light) and converts them to an electric charge.

This in turn is converted to digital data as a picture element or ‘pixel’.

Specialized manufacturing process to create the ability to transport charge across the chip without distortion.

High-quality sensors in terms of fidelity and light sensitivity.

 Use more power, 100 times more than CMOS -therefor use up battery faster.

 More specialized manufacturing process, therefore much more expensive

Use traditional manufacturing processes to create the chip -- the same processes used to make microprocessors for computers.

Therefore, inexpensive to manufacture.

Use very little power.

Can be manufactured on same lines as other processors therefore very cheap to produce.

Photodiodes or pixels are monochrome

They can only measure brightness levels or luminance. They cannot distinguish Red, Green or Blue.

Three-Chip colour capture

Colour sequential Capture

Integral Colour Filter Arrays

 Uses optics to split the scene onto three separate image planes 

[image]

 Three successive exposures while switching in optical filters

[image]

 Coloured filters are placed on the chip

[image]

Pros: Color images can be created with one exposure. Also high resolution preserved.

Cons: Complex registration, Requires 3 CCD’s therefore expensive, increases the size of the camera

Pros: high resolution preserved

Cons: need three separate exposures, this is not practical. Ok for scanners, but you can’t photograph a moving subject

Pros: Single exposure required, less complex

Cons: each pixel can only be patterned as one primary color. Therefore lose some information and reduced resolution. Requires interpolation (processing)

-relies on colour interpolation

-reduced resolution

-prone to colour errors

Digital cameras use specialized demosaicing algorithms to convert the Bayer array of primary colors into a final image which contains full color information at each pixel. This is done by averaging the values from the closest surrounding pixels.

RAW converters do this also.

Named after Dr. Bryce Bayer 1976 working for Kodak

[image]

Each square on the sensor is picture element or what we normally call a pixel.

A pixel is what actually captures the light Pixels counted by the millions.

One megapixel = 1 million pixels

Approx size of a pixel is 5 microns.

The ADC classifies ("samples") the analog voltages of the pixels into a number of discrete levels of brightness and assigns each level a binary label consisting of zeros and ones. 

The type of ADC will determine the bit depth that a camera can produce

ie. Canon 30D produces a 10 bit/channel RAW image.

256

A "one bit" ADC would classify the pixel values as either black (0) or white (1).

A "two bit" ADC would categorize them into four (22) groups: black (00), white (11), and two levels in between (01 and 10).

Most consumer digital cameras use 8 bit ADCs, allowing up to 256 (28) distinct values for the brightness of a single pixel.

[image]

256 red   x   256 green   x   256 blue

=

16,777,216 colors (16 Million Colours)

Professional level cameras have a 10 to 14 bit ADC. Capable of generating from 1024 to 16384 different brightness values at each photo site (pixel)

This is why we encourage photographers to use RAW format.

You are working with a 10-14 bit image instead of an 8 bit jpg image.

The dynamic range of a sensor is defined by the largest possible signal divided by the smallest possible signal it can generate.

The largest  possible signal is directly proportional to the full “well capacity” of the pixel.

The lowest signal is the noise level when the sensor is not exposed to any light, also called the "noise floor".

Sensors:

1. Fill Factor

2. Noise

3. Moiré Pattern

4. Low Pass Filter

Jpeg compression

Resizing

 The amount of a Pixel that is actually capturing light. Expressed as a percentage.

In an active pixel, both the photodiode and the amplifier take up "real estate" in the pixel.

The amplifier is not sensitive to light, so this part of the pixel area is lost when taking a picture.

CMOS sensors have small fill factor, (not a good thing)

The solution is an array of lenses called “microlenses” placed over the photodiode.

This can increase the fill factor by 2 - 3 times.

This is any unwanted electrical signal that interferes with the image being read and transferred by the imager. Noise is the presence of color speckles where there should be none.

There are different types of noise and different causes.

1. Heat: heat alone can cause electrons to become free (this is what the light is supposed to be doing). These electrons add to the voltage recorded for that photo-site. Heat is always present but is worse during long exposures. Sensors used in astronomy are refrigerated to prevent noise. Can be called dark current or thermal noise.
2. High ISO: a higher ISO is achieved by amplifying the signal we receive from the light photons. When we amplify the signal, we also amplify the background electrical noise that is present in any electrical system. In low light situations there maybe more noise then true signal.
3. Small sensor size: each photo-site itself generates electrical noise that can contaminate its neighbor. In a larger image sensor, the photo-sites can be physically further apart and thus be less affected by that contamination.
4. Small pixel size: In order to create higher mega pixel cameras, the pixel become smaller which in turn means small light gathering capacity. This causes a poor signal/noise ratio.

Lined pattern that appears when two regularly spaced sets of repeating lines are superimposed on the pixel array of a digital imaging device.

Moiré patterns occur when the geometric pattern of a photo subject changes at a narrower spatial frequency than that of the picture elements ("pixels") of a CCD or CMOS sensor.

(As explained by Canon website) Certain fabrics can have a very tight, regular weave. This can appear as a series of alternating stripes separated by dark shadows between the weave. When the pitch of this weave is close to a digital camera sensor's pixel pitch, light from the subject will only activate selected rows of pixels. The sensor will then produce false colours that appear as waves on the image, known as moiré. 

To combat the effects of moiré, camera manufacturers utilize a low pass filter to blur incoming light.

Usually spread out by one pixel in two opposite directions. Causes loss of sharpness, which is corrected by very complex algorithms.

This is handled by in-camera processors.

 -lossy compression

-using refined algorithms, it selectively discards image data

-results in smaller file sizes

-data is lost, each time a file is saved as a jpeg it is no longer identical to the original

-jpeg is designed to preserve detail at the expense of colour.

-Our eyes are more readily able to detect a change in brightness than a change in colour

-jpeg compression works by taking an RGB files and encoding them in a different color space called YCbCr. -YCbCr is made up of a Y(luma)(brightness) and Cb (blue chroma) and Cr (Red Chroma)

-most of the compression takes place in the Cb and Cr coordinates.

jpeg compression “preserve detail at the expense of colour”

-Once converted to YCbCr, then the images is divided into 8x8 blocks.

Each block is treated as its own unit and the compression algorithms are applied.

-look at your print closely or view your file at 300 percent and you may see some of the 8x8 blocks.

-You should not save a file as a jpeg, multiple times, since “compression artifacts” may accumulate and progressively degrade the image.

-As colours are dropped, posterization begins to occur.

This occurs when pixels are added or taken away. The file size actually changes.

Image editing software (and cameras) achieve this by interpolation.

Interpolation is a method of using known data to determine unknown data.

Resizing up from a small file (low res) to a larger file (high res) …. like taking an 8X10 to a 16X20

Essentially neighboring pixels are used to determine colour and brightness of newly generated pixel.

Interpolation also occurs when rotating an image or a selection within a file

1. Aliasing

2. Blurring

3. Edge halo

-Munsell

-RGB

-CMYK

-HSB

-CIE colour model (colour space)

 (1858-1918)

Developed one of the first successful and widely used colour models.

Colour Atlas

[image]

 By three values

Hue - color,

Value - Brightness of colour/or darkness

and Chroma

 Appearance.

More of a perceptual or psychological measure.

Simple, easy to understand -easy to communicate or visualize the colour

Similar to how our eyes define colour, but cannot create the full visible spectrum.

Usually only applicable to electronic devices which display colors.

For example, Televisions, and computer displays.

Also applicable to web designers and photographers.

Colour by numbers

Red, Green and Blue values

Each number value indicates how much of the primary is included.

The values range from 0 to 255

0 = black (minimum)

255 = white (maximum)[image]

Chromaticity Map

-a different way to specify colour

Also known as CIE 1931 XYZ

Commission internationale de l'éclairage

or

The International Commission on Illumination

Experiments using “standard observers”.[image]

A collection of random observers were asked to match various colours by mixing three coloured lights.

JND (Just Noticeable Difference)

This color space represents all the colors that are perceivable by the human eye.

Describes 2 attributes, hue and chroma (dominant wavelength and purity)

Outer edges are the wavelengths of light

 Purple band along bottom, are colours that do not have a correlating wavelength

Non-Uniform Colour Space

 While it is accurate and a convenient map of visible spectrum it has some issues

 The distribution is not uniform (more green)

 JND (Just Noticeable Difference)

[image]

Often referred to as CIELAB

Developed to address the “non uniform” colour difference in the Chromaticity map.

Based on simple colour vision model

Accounts for...

a) changes in colour,

b) amount of illumination,

c)compression

d) opponent signal processing.

Rendered as a 3D model.

(see coloursync utility)[image]

L* value = luminance Range of 0 (black) to 100 (White)

a* value = redness compared to greenness

b* value = yellowness compared to blueness 

Process of translating colour characteristics from one device to another.

In our case camera/scanner to monitor to printer/photo lab.

A system that transforms colour data encoded for one device into colour data for another device, so that the colours in each device match.

 Because different applications or mediums have different capabilities and different restrictions or limitations when it comes to reproducing colours.

A scanner will produce RGB values, and so does a camera...

but an R value of 150 from the scanner may not match R value of 150 from the camera. 

When we talk about colour management system we usually refer to those systems that use the internationally accepted CIE system of colour measurement as a reference and

...

make use of ICC profiles.

International Color Consortium

Essentially an association of over 70 businesses or vendors.

Goal: Create a vendor-neutral, cross-platform colour management system.

Created a profile system of colour management. Essentially a “device to standard” and “standard to device” transformation model.

Members include: Apple, Microsoft, Adobe, Kodak, Agfa, Silicon Graphic Inc. etc...

When you calibrate your monitor

Colour Space: a geometric and 3D map of the colours that a device can produce.

[image]

Device Dependent

and

Device Independent

Is a colour mgt system that depends on the user manually making uniques adjustments to equipment and to produce correct colour.

Does not use ICC profiles.

-unique adjustments (corrections) between each device.

-one adjustment when going from one computer to a printer, and then another adjustment when going from a different computer to the same printer. etc...

-time consuming, inefficient.

Is a colour mgt method that uses a constant reference called a Profile Connection Space (ie. CIELAB colour space, 1931 CIE Colour Space) to map the colour space (profile) of one device and use that information to correctly translate that colour information to another colour space.

-each device has its own unique profile.

-this profile is like a map within the CIELAB colour space.

-CIELAB is like a universal/independent translator 

Used as a reference between devices.

Holds the coordinates of 2 device profiles for “gamut mapping”

This reference space or PCS is larger than the colour space of either of the two devices.

CIELAB: Developed in 1976

-Used as a device-independent reference colour space

-allows for different colour systems to “speak” to one another.

-does not matter if Mac or Pc, if monitor, scanner or printer

-Used in many colour mgt systems.

A rendering intent defines how the gamut of colours which can be achieved on one media is modified when reproduced on a media with a different colour gamut.

It defines the method used to convert between colour spaces.

Defines how to deal with “out-of-gamut” colours

1) gamut clipping

2) gamut compression

What is Gamut Clipping?

Each out-of-gamut colour is is mapped to the closest colour that is “in” gamut (Image on the left)

-Several “input” colours can be mapped to the same “output”colours.

-This can cause a loss of tonal variation in some areas

[image]

The larger “input” gamut is compressed to fit inside the smaller “output” gamut

-the smaller gamut is first compressed in order to create space for the incoming gamut.

-this will change all the colours in the image

(Perceptual : Image on the left)

[image]

Compresses all colours into the destination space.

-Most often used when going from large gamut to a smaller gamut.

-Preserves the visual relationship between colours. (Gamut compression)

-Preserve luminance and brightness over saturation and hue (Image on the right : Perceptual) 

-Used mainly for pictorial images. Photography

[image]

Near 1 to 1 matching of in-gamut colours while out-of-gamut colours are clipped to the nearest reproducible hue. Used when going from large gamut to large or similar gamut size.

-Also common with photographic images

[image]

Primarily used with graphics, illustrations etc.

-tries to map out-of-gamut colours to other highly saturated colours.

-results in colour shift, but this is rarely a concern

Strict colour conversion

-Used for creating proofs

-primarily concerned with matching the “whites” of output device or media.

Colours are shifted accordingly.

When one combines complimentary colours in the correct proportions, neutral colours are produced.

Combine Red with Cyan

Green with Magenta

Blue with Yellow

Have no hue or saturation and are sometimes called achromatic colours.

They can vary in brightness levels from black to white. (greyscale)

Not really an absence of colour.

Greys appear neutral because they do not alter the colour balance of incident light.

In other words equal amount of all the colours reflects and reaches the eye. 

One of the critical tests of a photographic system, (printer, display, camera sensor, etc) is how well it reproduces neutral colours.

Small variations in colour balance can be detected more easily with neutral colours.

To our eyes something is either neutral or not

Perfect colour matching is not possible but the result should be a pleasing approximation to the original colours. In general the term colour management system is usually reserved for those systems that use the internationally accepted CIE system of colour measurement as a reference.

Set of practices that insures a predictable output from digital files.

Defines colour in terms of the three subtractive primaries. Cyan, Magenta, Yellow.

Essentially used in colour printing CMY values often indicated as a percentage of that ink colour used.

Non-impact Printer … compared to the Type Writer

Also known as “Drop on Demand” or DOD

This means ink is squirted onto paper.

Essentially an array of tiny nozzles to create millions of ink droplets, placing them in precise combinations onto the paper.

Invented by Canon and Hewlett-Packard (HP) almost at the same time:

Canon … an engineer noticed ink squirting from the neck of a syringe when a hot soldering iron touched it

Hewlett-Packard … a researcher borrowed the mechanism of the coffee percolator

Use heat to project ink through a nozzle and onto the page.

1. An element in the print head heats up ink

2. The hot ink forms a bubble, it expands until it bursts in the chamber, “splashes” onto the paper.

3. The element and the chamber cool, create a vacuum and draw ink back into the chamber

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Piezein is a Greek word for squeeze or press.

1. An electric current makes a Piezo crystal change shape. 2. This squeezes the ink out of the nozzle onto the paper. 3. As the Piezo crystal returns to its normal, shape, a vacuum is created and the chamber is filled with ink again.

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 Print Head contains 112 nozzles:

64 nozzles for black 48 nozzles for colour

(16 for each colour)

Refers to a dot on the paper.

A dot can be made up of several droplets.

Factors that affect “printed dot” size:

-paper surface, and absorption.

-half-toning method

-variable size of droplets

(if printer supports this)

"Dots Per Inch" has been the traditional measurement and indicator of a printer's output quality and refers to how many dots of ink are placed on each inch of a piece of paper or other media by a printer.

Resolution is a measurement of a printer's quality and is traditionally measured in dots per inch (DPI)

ie. Epson printer can pump out 180 droplets of one colour per inch.

(7 droplets per mm).

If the printer uses 8 colours...

(Blck, LBlck, LLBlck, Mag, LMag, Cyan, LCyan, Yell)

Then 180 x 8 = 1440 DPI

(2 passes, means 2880)

1. Carrier Fluid: keeps ink liquid and carries the colorant. This is what evaporates when it strikes the paper, leaving the colour behind. ie Water

2. Additives: affect drying time, viscosity, fade resistance, brighteners. etc.

3. The colorant: either Dye or Pigment.

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Dye:

-True solution.

-dissolves fully into the carrier fluid.

-should never separate

(Think of food colouring mixed into water)

Pigment:

-Fine powder dispersed throughout carrier fluid

-never really dissolved, always a “powder”

-May separate over time.

-There is a shelf life.

(Think of orange juice mixed from frozen concentrate)

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When two colours look the same in one light source but different in a different light source

All look the same in daylight

Colours different in tungsten 

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 Dye is stored in a Ribbon the size of the paper being used Ribbon and paper will move through rollers and heating elements that change temp. rapidly.

Some of the dye “diffuses onto paper

Produces true “continuous tone” much like a “chemical” photograph

Used at events because they are fast

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Brightness refers to the percentage of light a paper reflects.

It’s one of the most important parameters used to judge a paper’s value and suitability.

 Even casual users of paper can perceive differences in brightness, and will find a whiter sheet generally more appealing.

1. TAPPI Brightness

(Technical Association for Pulp & Paper Industry)

(also GE scale)

2. ISO Brightness

(European)

Newsprint ranges from 55-75 ISO brightness.

Writing and printer paper would typically be as bright as 104 ISO.

The Dmin value of a film, scanner or printer describes the brightest white it can reproduce, measured as an optical density.

For a printer, Dmin refers to the optical density of the paper stock

The Dmax value of a film, scanner or printer, describes the darkest black it can reproduce, measured as an optical density.

For a printer, Dmax refers to the optical density of the darkest black it can output

Because it expresses the quality of the printer and paper combination.

Manufacturers continually strive to increase the dynamic range of their printers.

In other words increase the tonal range.

They can’t change the “white” of the paper, but they can make the blacks “blacker” so Dmax is often an key indicator of quality.

 Matte paper has a Dmax of approx 1.4

Glossy paper has a Dmax of approx 2.1

4 is considered maximum.

This means that nothing reflects back.

However, some light always does, so this is impossible.

Gloss differential is a phenomenon that is exhibited when the shine and thickness of the applied ink is greater than the shine of the plain paper where no ink is applied.

(white areas)

Only occurs with glossy and some luster or other “shiny” papers.

Does not happen with matte surface paper

Sometimes called "Differential of Sheen" is when dark areas appear to be less reflective than other areas in the print.

Glossy prints are especially prone to this problem.

Newer printers and newer inks have minimized this problem

What is Giclee Printing?

(Zhee-klay)

This process uses pigment inks (8 to 12) and archival papers to produce prints that are estimated to last 80 to 120 years before there will be any detectible colour shift in your image.

Usually reproduction prints of artists original. Colour accuracy and stability is a priority