[Groseph_Dirt]

CMYK_HAX gfx begginer's knowledge reference
I made this for every good artist that needs a good reference.

Intro to Graphics

Lets start simple.

Graphics file formats differ in the way they represent image data (as pixels or as vectors) and in compression technique.
Image files are composed of either pixel or vector (geometric) data that are rasterized to pixels when displayed (with few exceptions)
in a vector graphic display. The pixels that compose an image are ordered as a grid (columns and rows); each pixel consists of
numbers representing magnitudes of brightness and color.
A few exceptions (for instance Large Document Format (PSB), Photoshop
Raw, and TIFF), most file formats
cannot support documents larger than
2 GB.

Image file sizes

• Are expressed as the number of bytes— increases with the number of pixels composing an image, and the color depth of the pixels. The greater the number of rows and columns, the greater the image resolution, and the larger the file.
•Each pixel of an image increases in size when its colour depth increases—an 8-bit pixel (1 byte) stores 256 colors, a 24-bit pixel
(3 bytes) stores 16 million colors, the latter known as truecolor.

The question now with so many possible answers very quickly becomes, which one should I use?

Issues to keep in mind when choosing format.

• size
• compatibility to OS's
• compatibility to image type

File Formats Defined

Spoiler (Click to View)

TIFF - Tag Image File
Format (.TIF files)

• format of choice for use for master copies scanned data
• developed by Aldus, before Adobe bought them out
• large file
• lossless compression
• most universal format
• there are many TIFF variations
• some TiFFs allow inclusion of metadata
• RGB - 24 or 48 bits

TIFF/IT-P1 - Prepress
Interchange Standard (.TIF/
ITP1)

• used to describe process color documents
• developed for use with high end color prepress systems
• large file
• lossless compression
• favored by magazine industry for electronic ad submissions

JPEG - Joint
Photographic Experts
Group (.JPG files)

• format for scanned photographs used on websites or for sending
your photographic images in email
• JPEG uses a lossy compression, that is, some quality is lost when the file is written (saved), and it cannot be recovered.
• NOT suitable for storing a master copy of your data.
• JPG is mathematically complex, very similar in process to digitizing sound, and requires considerable CPU processing power to decompress an image.
• good JPG compression values for routine use are 75-80%
Quality, or 20-25% compression.
• harmed most by compressionare sharp contrasty edges, like
text letters, graphic art, etc.
• RGB - 24 bits Compression-

ORIGINAL from which Histrograms were derived from:

JPEG Histrogram
(First save)

JPEG Histrogram
(Second save)

JPEG 2000

• supports optional lossless compression
• 16 bit color or grayscale files
• 8 bit transparency
• can retain alpha channels and spot channels
• supports Grayscale, RGB, CMYK, and Lab image modes
• can be used for both web and print publishing

GIF - Graphic
Interchange Format
(.GIF files)

• developed by CompuServe
• relatively small compressed file sizes
• limited to only displaying 256 colors, but can select from millions
• GIF is the smallest file for 16 or 256 color data like graphic art or
screen captures
• fewer colors, the smaller the GIF file. Size is important to web
pages. "
• lossless compression
• offers transparent backgrounds
• good for line art

Camera raw files (.dng)

• contains unprocessed picture data from a digital camera’s image sensor
• the image data is interpreted in Photoshop rather than having the
camera make the adjustments and conversions automatically
• contains the actual data captured by the sensor without any in-camera processing
• allows user maximum control
• allows setting the white balance, tonal range, contrast, color saturation, and sharpening
note: Think of camera raw files as a photo
negative. You can reprocess the file at any time to
achieve the results you want.
• only available on some proconsumer cameras and higher
• supported on Photoshop 7.0 and higher
• ultimate control over processing
• adjustments made using much more powerful and versatile software on a PC
• originals can be kept as RAW files, much like traditional negatives and archived, as newer software should bring nowunknown advantages to older RAW files
• proprietary format and frequently vary from model to model
• main disadvantage is the time required for post-processing
• requires long time to write to memory cards

Encapsulated PostScript
(EPS)

• can contain both vector and bitmap graphics
• widely supported
• used to transfer PostScript-language artwork between applications
• supports Lab, CMYK, RGB, Indexed Color, Duotone, Grayscale, and Bitmap color mode
• supports clipping paths

Desktop Color Separations
(DCS 1.0 and DCS 2.0)

• EPS file that supports up to five (DCS 1.0) or six (DCS 2.0) plates and a master image
• supports grayscale, RGB, spot colors and CMYK
• faster than standard EPS files
• can contain both vector and bitmap files

BMP (Windows Bitmap)

• A. large file size
• B. BMP is lossless like TIF.

Macintosh Quickdraw
(PICT)

• limited to 256 colors
• PICT is used in page layout and graphics programs

Windows Metafile (WMF)

• limited to 256 colors
• Windows equivalent to PICT

Photo CD

• proprietary format of Eastman Kodak
• can contain only raster information
• supports grayscale, RGB and CIELAB color models
• basically obsolete

Native- native to particular software

• normally compact
• normally openable only by software that created it
• contains special features of that software

Digital Print Order
format (DPOF)

• designed for digicam
• define which captured images on the storage card are to be printed
• usually consists of a set of text files in a special directory on the storage card which are accessed to print the desired

Exchangeable Image File
(EXIF)

• used by nearly all digital cameras to store extended camera information such as ISO-speed, shutter time and aperture
• stores the information in the header of each JPEG file
• uses sRGB as the default color space quantity

Portable Network
Graphics (PNG)

• can be 24-bit or 8-bit
• use a lossless compression scheme
• PNG images are interlaced
• support 8-bit transparency
• include the ability to correct for gamma information based on the
computer monitor on which they are

Spoiler (Click to View)

Typical file sizes produced by an 8-megapixel Camera

• RAW (12-bit NEF) 11MB
• HI (8-bit RGB TIFF) 23MB
• FINE (High-quality 8-bit RGB JPEG) 3.6MB
• NORMAL (Standard 8-bit RGB JPEG) 1.6MB
• BASIC (Highly compressed 8-bit RGB JPEG) 0.9MB

Take a look at the drop shadows in the graphics above and compare them to the ones i made before, the ones above were done on a different cpu and monitor. Now looking at both graphics on two different monitors and machines side by side they almost look identical. This problem arise's when you dont utilize a set of universal standards in house. If I had calibrated both monitors and machines to the same standards and imported my settings then they would match, but instead I did it by eye off of the other one. Avoid not taking the time to calibrate.

Explaining Resolution and Screen Ruling

Spoiler (Click to View)

Terminology

• Halftoning- process used to convert a continuous tone photograph into a patten of tiny dots
• Imagesetter- device that exposes film using a fixed grid of laser exposures.
• Raster Image Processor (RIP)- required of all Postscript printers to interpret information sent by computer to controlling marking engine of imagesetter.
• Dot Percent- way of describing the gray value of an area of dots. Shades of gray get darker as the dot area
increases.
• Screen Ruling- measure of the fineness of a screen - the higher the number, the finer the screen. A 150 line per inch
screen has 150 dots per inch in both the vertical and horizontal direction.
• Screen Angle- orientation of the screen. Normally a black and white halftone is oriented at 45 degrees.
• Number (or Level) of Grays- relationship between the resolution of the halftone ruling and the imagesetter resolution.
• Resolution(imagesetter)- the result of a combination of factors including addressability and laser spot size.
Addressability is a measure of how many laser spots an imagesetter can produce within a linear inch.

Halftone cells are created by clusters of laser spots. These spots are locked into the resolution capabilities of the
imagesetter.

Laser Spots are Fixed to Grid

• The lower the resolution,the less smooth the angle.
Laser Spots are Fixed to a Grid


Required Screen Angles
• 45 (Black)
• 75 or 135 degrees (Cyan)
• 15 or 105 degrees (Magenta)
• 90 degrees (Yellow)


Making Angles on Grids
• 45 (Black)
• 75 degrees (Cyan)
• 105 degrees (Magenta)
• 90 degrees (Yellow)

Trigonometry raises its ugly
head

• To ensure the dot fitting on the grid, its angle must be a rational number.

What’s rational about it?

• A rational number is one that can be defined as an integer or a ratio of two integers. An angle with a rational tangent is one where the opposite and adjacent legs of the triangle are integers.

What’s an integer?
• A positive or whole number, i.e., 1,2,3 or -1,-2,-3, or 0

Rational integers illustrated:
• The opposite side is one unit and the adjacent side is three units



Required Screen Angles
• 45 (Black)
• 75 or 135 degrees (Cyan)
• 15 or 105 degrees (Magenta)
• 90 degrees (Yellow)

What about 15 degrees ?

---

Digital Halftone Cell continued

Spoiler (Click to View)• A digital halftone cell is the imaginary boundary of a halftone dot

• Each cell is subdivided by the number of laser spots that create the image
• The more laser spots the more variations in tone available per cell
• A tradeoff occurs
• The more variation the bigger the dot and the coarser the halftone line ruling.

Supercells

• If the cell becomes large enough you can achieve the rational halftone angles at almost the 15 and 75 degree angles.
• For example an imagesetter that has a resolution of 2540 can produce a screen angle of 15.018 at a screen ruling of 42.45.
• By using this huge halftone cell and subdividing it into smaller halftone cells you get a useable halftone angle and
line ruling.
• You also create halftone cells of different shapes

Reproducing Density, Tone and contrast

Density- ability of a material to absorb or transmit light
• Densitometry is the science of measuring the different densities in the graphic arts industry.

Two Types of Density

• Reflection - is a measure of light reflected from an area of the copy.
• Reflectance =
R= Ir
Irw
• R = reflectance
• Ir= intensity of light reflected from copy
• Irw =intensity of light reflected from white paper

• Transmission - amount of light transmitted through the copy
• Transmittance =
T=It
Ii
• T = transmittance
• It= intensity of transmitted light
• Ii =intensity of incident light

• A density reading is nothing more than a logarithmic scale ranging from 0.0 to over 4.0 that equates a numeric value to the
relative ability of a material to absorb or transmit light

How to measure density?

Two broad categories of densitometers

How they work

– Visual densitometer
– Photoelectric densitometer

What they measure

– Reflection densitometer
– Transmission densitometer

Tone and Contrast

Line Copy

• a Line copy is high contrast.
– It is made up of areas that are either white or black

Photographs are reproduced by being converted into a “halftone.”

Halftone copy

• Black and white photographs are continuous tone having a continuum of white to black tones.
• These different densities give the copy contrast and detail.
• To recreate these different tones using conventional printing processes is impossible.
• To represent these tones, they need to be converted into different size dots. The resulting image is called a halftone.

• Four factors in every good halftone
– A. correct size dots
– B. correct number of dots
– C. correct contrast
– D. right screen angle
Each of these factors are dependent upon the printing process, substrate and viewing distance

• Three Main Tonal Areas of a Halftone
A. highlight
1. specular (reflection)
2. diffuse
B. shadow
C. midtone

• Two Additional Tonal Areas of a Halftone
– A. quartertone
– B. three-quartertone

Halftone Screens

Screen Rulings Explained

• Normal viewing distance
• Process of reproduction
• Type of substrate

Typical Screen Rulings
• 45
• 85
• 110
• 133
• 175
• 200
• 65
• 100
• 120
• 150
• 185
• And beyond

Dot Size and Shape

• Square Dot
• Elliptical Dot
• Circle Dot
• Special Shape
• Conventional Square Dot from 5-95%

Elliptical /Square Dot Shape Comparison


Measuring Dot Area

• Visual Inspection
• Dot area meter

How are Dots Created?

Theyre Created on a grid of fixed spots

Digital Dots

• Cell Size is related to levels of gray
• (cell size +1)=levels of gray
• Simple choice Levels of Gray Or Number of Dots
note: As levels of gray decrease, number of dots increases[/spoiler]

---

PART 2

Color Theory, Color management, Calibration

Heres some stuff you will want to know:

CMYK vs RGB

Spoiler (Click to View)CMYK
A CMYK workflow is based upon intended print characteristics.
-CMYK images are "committed" to that color space ensuring an accurate print.
-CMYK is subtractive color, Mixing the various percentages will yield about 1 million colors (100 x 100 x 100 = 1,000,000).
-So if CMYK is subtractive color, the color of the paper -- your starting point -- is a key component of achieving good color and that is the color of the paper.

RGB
RGB files have three channels and are therefore smaller.
• More filters work in RGB in Photoshop
• RGB files are not committed to any reproduction method
• RGB reduces the number of color conversions
- RGB is additive color, this is because you’re starting off with no color, a black screen, and adding color.
a.Unlike the shades of colors in CMYK, which are varied using dots, RGB color shades are varied by using levels of brightness from the electronic source: a cathode ray tube (CRT), a liquid crystal diode (LCD), or from another electronic methods. Also, unlike the percentage of dots in print that comprise 100% offering 100 variations, there are 256 (0 to 255) shades or levels of brightness for on-screen color that generate 16,777,216 (256 x 256 x 256) color possibilities

So basically on-screen color is RGB and print is CMYK. In effect, the two are opposites since again, one is subtractive
color and the other is additive color. When you manipulate and create images in the digital environment, it’s all RGB -- although
programs like Adobe Photoshop allow you to convert to CMYK and effectively simulate the CMYK color space on-screen. (Photoshop is
actually working behind the scenes in another color space but let’s not get into that.) The key point is that since on-screen is RGB,
you have to convert to CMYK to print.

RGB Gamut

Cmyk Gamut

Color Theory

Spoiler (Click to View)CIE 1931 Chromacity Diagram

There are two types of data when speaking in reference to color theory.
SPECTRAL DATA
• Spectral data describes the surface properties of the colored object by demonstrating how the surface affects (reflects, transmits, or emits) light.
• Conditions such as lighting changes, the uniqueness of each human viewer, and different rendering methods have no effect on these surface properties measured as spectral data.

The second kind is TRISTIMULUS DATA
• Tristimulus data describes how the color of the object appears to a viewer or sensor, or how the color would be reproduced on a device such as a monitor or printer, in terms of three coordinates or values.
• CIE systems such as XYZ and L*a*b* locate a color in a color space using three-dimensional coordinates.
This differs from a color reproduction system.
• Color reproduction systems such as RGB and CMYK describe a color in terms of values that can are mixed to generate the color.

So what do x,y,z and L*A*B* values mean?
• High X= Red
• High Y= Green
• High Z= Blue

L*A*B* Diagram
img
• An important difference between the x,y, chromacity diagram and the LAB diagram is that the LAB diagram has better perceptual uniformity

• L= lightness
• A= Red (positive) Green (negative)
• B= Yellow(positive) Blue (negative)

Telling the Difference in Colors

Delta-E is used to describe (mathmatically) the distance between two colors.
• To calculate the delta-E of any two colors, you need to know their LAB values.
• The average, casual viewer can notice the difference between two colors that are 5-6 delta-E apart.
• A trained eye is capable of differentiating two colors that are closer to 3-4 delta-E apart.
• However, the human eye is very sensitive to changes away from achromatic tones (a and b values near
0)--in this case, you can often notice a difference between two 'shifted' grays that are as close as .5 delta-E apart.
• To calculate Delta E, use the following formula

• Tolerances of less than 2 delta units are typically unachievable given normal process variation.

Color Management

Spoiler (Click to View)

Why is color management important to you?

It ensures that all aspects of your color images integrate seamlessly with production partners and reproduction devices.
-The value of color management increases when you have more variables in your production process.
Goals of Color management:
- make color reproduction easier
• makes color reproduction more accurate
• remove frustrations and unknowns in the reproduction cycle

Color Profiles - color profiles are a set of standards embedded in your image ensuring consistent reproduction on multiple
devices.
The use of profiles offers:
• accurate and consistent reproduction between devices
• ability to use monitor as soft proofing device
• device simulation
• gamut checking and mapping
• profile embedding

Focus on your rendering intent when choosing a color profile.
Rendering Intents are specifications useful in choosing a color profile.

Relative Colorimetric Rendering Intent
• Clips colors outside the gamut
• Colors within gamut not changed
• Uses white point of destination and adjusts to it
• Reproduces colors relative to the white points of the respective substrates of the original
and reproduction

Absolute Colorimetric Rendering Intent
• Great for logo colors tat must be reproduced accurately
• Creates exactly colors of the original
• Matches white point of both original in the reproduction

Saturation Rendering Intent
• Moves in gamut colors toward edge of destination gamut for maximum
saturation and impact

Popular color profiles:
sRGB-monitors
SNAP-newsprint
SWOP-webfed offset such as magazines

Calibration

Spoiler (Click to View)How to go about producing Consistent Color?
Calibrate your monitor
• When you calibrate your monitor, you are adjusting it so it conforms to a known specification.
• This is a color profile.
• Profile describes:
a. what colors can or cannot be displayed on the monitor
b. how the numeric color values in an image must be
converted so that colors are displayed accurately.
• Make sure your monitor has been turned on for at
least a half hour.
• This gives it sufficient time to warm up and produce
more consistent output
• Make sure your monitor is displaying thousands of colors or more.
• Ideally, make sure it is displaying millions of colors or 24‑bit or higher.
• Remove color background patterns on your monitor desktop and set your desktop to display neutral grays.
• Busy patterns or bright colors surrounding a document interfere with accurate color perception.
• Do one of the following to calibrate and
profile your monitor:
• In Windows, install and use a monitor calibration utility.
• In Mac OS, use the Calibrate utility, located on the System.

For the best results, use third-party software and measuring devices.(I use a spyder 3 its like $300 but thats pretty cheap for one)
In general, using a measuring device such as a colorimeter or spectrophotometer along with software can create more accurate profiles because an instrument can measure the colors displayed on a monitor far more accurately than the human eye.

Note: Monitor performance changes and declines
over time; recalibrate and profile your monitor
every month or so. If you find it difficult or
impossible to calibrate your monitor to a
standard, it may be too old and faded.

Next i would recommend you import profiles from all of your reproduction devices.
(any input and output devices you plan to use, such as scanners and printers.)
-If your document will be commercially printed, contact your service provider to determine the profile
for the printing device or press condition.

IT IS IMPORTANT TO Choose a standard color management configuration and synchronize color
settings across applications before working with documents.
How?
• Either choose Edit > Color Settings or Preferences>Color Management
• Select a color setting from the Settings menu, and click OK.
The setting you select determines which color working spaces are used by an application, this is what happens when you open and import files with embedded profiles, and how the color management system converts colors.

If your doing work for a client over the web being able to accurately preview colors how they'll be reproduced will save you alot of time and effort.
• In a color-managed workflow, you can use the precision of color profiles to soft-proof your
document directly on the monitor.
Keep in mind that the reliability of the soft proof depends upon the quality of your monitor, the
profiles of your monitor and output devices, and the ambient lighting conditions of your work environment.

[muzzy.]

HQ thread! Deserves more love, no idea why it's been ignored.

[Groseph_Dirt]

ty
i wish it had more feedback on possible mistakes.
if theres anything you think i should add let me know.

[Nick]

Amazing thread! Deserves to be viewed a lot more then it is right now! Thanks for this too!

[Cyarkia]

Thanks for this, I learnt quite a few things from it :)

[Judecca]

For a beta, not bad kid. Seems like you put some nice effort into this.
Professionally presented, I liked this.

Well done indeed...

[Groseph_Dirt]

For a beta, not bad kid. Seems like you put some nice effort into this.
Professionally presented, I liked this.

Well done indeed...

Beta/rep/money dont matter.
Only the quality and consistency. This place helped me out alot when i really needed it, I dont post unless its an answer, tutorial, or feedback (a few exceptions to be funny).
I wouldnt waste anyones time with anything else but I do sincerely enjoy the feed back.

I've tried posting several times in the Gfx section but it seems pretty dead in there normally.

(Btw i'm no kid, I just wasnt aware of this place's existence. This should have been my home long ago.)

[Judecca]

That's it. Keep up like that, and you'll go even further.
I've seen your posts and you seem to be very HQ.

It pleases me to see that attitude in your posts.

I expect to see alot from you. We'll keep in touch.

[Conch]

Very HQ Tutorial.
I'm going to read through it now, I just started Image editing, Illustration and Flash.
This will really help.
Thank you!

[Eminent]

Although the thread graphics used here could be a lot better considering it's a graphics tutorial, the content was great, technically, and very informative. Nice job

[Groseph_Dirt]

Although the thread graphics used here could be a lot better considering it's a graphics tutorial, the content was great, technically, and very informative. Nice job

i know i made funky headers but there was a point to that.
I intially had better ones like the first graphic, but i scraped them to make a point(the paragraph below halftones and resolution). That example tells you exactly why color calibration is important between machines in your your workflow.

If i could edit the post i would church it up a bit, but sadly i am unable.

[KrashOPS]

Been using Photoshop without most of this knowledge for years. This is not so basic... This is like the entire Photoshop science. Big ups for the tutorial, was really usefull and informative.
Keep up the good work!

[Unrep]

Well, after skimming over this it seems quite fine, although the title images you used are somewhat ironic.