Week 4: Image Editing

Week 4: Digital Images & Image Editing

Vector Graphics Versus Raster Graphics

Vector graphics, known as object graphics in the text, are drawn mathematically in the computer with points, lines, curves and filled-in areas. These kinds of objects can be enlarged or reduced in size without losing quality, and they tend to be low in file size.
Vector drawing is usually best for logos, illustrations and other simple graphics. The drawings consist of outlines, filled-in areas, or both. The filled-in areas can contain solid colors, gradients, or patterns. In most cases, transparency and other effects can be used with vector graphics.
Raster graphics, known as pixel graphics in the text, are drawn pixel-by-pixel in the computer. This kind of drawing is ideal for photographs, in which neighboring pixels are usually different colors from each other. Most web graphics must be displayed in raster format (such as JPG, GIF, and PNG files.)
Below are two comparisons of the same image drawn pixel-by-pixel (raster) versus mathematically (vector.) The raster images are on the left and the vector on the right. The second set is zommed in to show detail.


Raster versus vector graphics, zoomed out and zoomed in.

Vector Graphics

Programs

• Adobe Illustrator
• Adobe Flash
• Adobe Fireworks
• CorelDRAW
• Others...

File Formats

• PDF (Portable Document Format)
• EPS (Encapsulated PostScript)
• AI (Adobe Illustrator)
• WMF (Windows Metafile) and EMF (Enhanced Metafile)
• SVG (Scalable Vector Graphics)
• Others...

Raster Graphics

Programs

• Adobe Photoshop
• Corel Painter
• iPhoto
• Microsoft Paint
• Others...

File Formats

• JPG (Joint Photographic Experts Group )
• PSD (Photoshop Document)
• GIF (Graphics Interchange File)
• TIFF (Tagged Image File Format)
• PNG (Portable Network Graphics)
• BMP (Bitmap)
• RAW (different file formats, depending on make of DSLR camera)
• Others...

Color Modes

Resolution

Compression

Dithering

On edges which are not perfectly straight up or down, raster programs such as Photoshop smooth out the jagged look of whole-pixel colors by using dithering. Dithering is a way of blending one color into another by using a small band of pixels between the two which provide a gentle transition.

Artifacting

Content for this week's lesson is not yet complete.
Sample of Artifacting
Logo saved as a JPG:


Same logo saved as a GIF:



Finally, saved as a PNG-24:

Assignment

Homework

Bring in 3 or 4 images on paper ready to scan. They can be photographs, orginal artwork, printed matter, etc.

Images Scanned and Edited

You'll want to be taking notes as you do steps 1 and 2 below, so that you are prepared to complete step 4.

1. Scan in 3 or 4 images.
2. Edit them in Photoshop and prepare them for the press.
3. Arrange them within an InDesign document on one or more pages.
4. Next to each image, describe:
• The nature of the original document
• The settings you used to scan it in
• The edits and adjustments you used in Photoshop to improve the image, in the order completed
5. Save the document as a PDF [Press-Ready] called images.pdf.

Portal

4

2/5/2016

Image Editing

Images Scanned and Edited

images.pdf

50

2/12/2016

 Student Showcase

We will take a look at any of your new work which is ready to share.
For the comparative poster project, we will discuss the following aspects:

• Overall strength of the design
• Degree to which:
  • the file is built correctly
  • the content is correct and comprehensive

Digital Photography

Digital Cameras

• Use the same optic techniques as film cameras, but the film is replaced by an image sensor which registers light reflected off the subject and read as RGB.
• Advantages of digital photography:
  • easy to determine right away how well the image turned out
  • easy to adjust the exposure to improve your results
  • no extra expense to take many exposures
  • saves resources because film and film developing are not needed
  • automatic digitizing of the image
  • some digital cameras take video as well
• Disdvantages of digital photography:
  • better digital cameras are more expensive than corresponding film cameras
  • the image sensor is smaller than the surface area of photo film, reducing the short-range depth of focus
  • greater risk of color refraction errors
  • poorer dynamic range (more difficulty reproducing tones in darker areas of the image, and more noise in tricky light situations)
  • less sensitive to color temperatures of light
  • the number of megapixels a camera can record does not tell us about the image quality to camera can attain

Taking Pictures for Print

• Avoid low light—it adds noise and increases the required exposure time
• Avoid slow shutter speeds—typically the camera or the subject move during the exposure
• Use a tripod when a longer exposure is needed
• Use a white or gray surface to help adjust brightness
• Avoid photographing in direct sunlight—it can reduce color range
• Plan ahead—since there is typically a lag time in turning on, focusing, setting the exposure, and saving to memory
• Store images in RAW or TIFF format within the camera, if possible
• Avoid "digital zoom"—it does not increase image detail
• Use a separate flash apparatus indoors

Scanning

Scanners

• A scanner reads an original image and converts it into a digital image for viewing and editing.
• Three main types:
  • flatbed scanner—original artwork is placed on a flat glass plate; light from a lamp is reflected on the artwork and passes to CCD (Charge-Coupled Device) cells
  • drum scanner—original artwork is mounted on a glass drum; light passes through the original film and through the rotating drum, then the light is led via mirrors to the CCD cells
  • film scanner—scans slides or film negatives; similar to a drum scanner but the film stays still rather than rotating
• What determines scanner quality:
  • quality of the CCD cells
  • optical precision and mechanical precision
  • tonal range, including tiny color changes
  • bits per color ("bit depth")—scanning with more tonal range than the final images means you have more image information to work with
  • scanner resolution, in pixels per inch
  • noise level (extra graininess can occur when the scanner and CCD cells heat up)
  • speed
  • image scanning software can give you advanced options

Scanning for Print

Original Images
The following aspects of the original image will determine how well your scan turns out:

• source (hand-drawn, printed, photocopy, etc.)
• size/resolution
• life span (e.g. Polaroid versus archival print)
• tonal range
• amount of detail
• graininess/noise
• location in the image of the greatest amount of detail (e.g. shadows rather than midtones)

Scanning Resolution

• The relationship between the size of the original image and the print is called the scaling factor.
• Your ability to enlarge an image is determined by
  • the final desired resolution
  • the maximum scan resolution of the scanner

Using a Scanning Application
Scanning requires the use of software which tells the scanner what settings to use.

• Remove dust and dirt thoroughly from the original and from the scanner glass.
• A preview of the image is taken quickly in order to see the placement of the original on the scanner bed.
• Select the area of the preview you want to be scanned.

The initial preview. Click the image above for a full-size version.

• Scan the image as closely to the desired result to facilitate any further editing and attain the highest possible image quality:
  • color correction
  • contrast and lighting
  • size and resolution
• Exception: do not sharpen the image during the scan. This should always be the last step after image editing, typically done in Photoshop.

Color, lighting, and resolution settings. Click the image above for a full-size version.
Resize settings and output data. Click the image above for a full-size version.
Avoiding Moiré Patterning
Use Descreen to help avoid moiré patterns which can occur when scanning an already-printed image and printing it again. Moiré is caused by the fact that the printing press prints patterns of dots.

Two overlapping patterns of printed dots causes moiré.
Click Descreen to avoid moiré patterns.

Example showing the interference or Moiré patterns on the left. On the right the Descreen filter cleans up the noise, but the image will be slightly blurry. You can sharpen it to some degree in Photoshop.
Batch Scanning
You can scan a number of images all at once, then crop them in an image editing program.
Four photographs are placed on the scanning bed at once and scanned into a single image.
In Photoshop, you can automatically divide the scan into individual images, using File > Automate > Crop and Straighten Photos.
Crop and Straighten Photos may not always result in perfectly cropped or straightened photos, but it does and admirable job of dividing the scan into individual images.

Evaluating Image Quality

Images of high quality:

• were photographed in an optimal way
• free of damage
• are of the highest possible resolution
• are adjusted and retouched carefully and correctly
• have colors whcih are natural and appropriate for the subject
• have good contrast and color range
• have low noice level/graininess
• have sufficient detail
• harmonize with other images within the same printed product

You should always keep a high-resolution, corrected but unresized Photoshop version of every usable image, so that they can be adapted for many uses without ruining your originals.

Image Adjustments

It requires one or more courses in image editing toobtain a thorough understanding of making images their very best for press. This will simply be an overview with a few tips specific to prepress.
The tasks listed below are in a specific order: the order in which you should complete them in your workflow. This pattern will assure the highest quality final product. If you edit images in a haphazard way, you can end up throwing away data (pixel information) in one task that you would have needed for best results in a task you complete later.

Rotation and Perspective

Use the Ruler tool to rotate a crooked photo.

1. Click-and-drag along an edge that should be horizontal.
2. Select Image > Image Rotation > Arbitrary.
3. Click OK.

To fix perspective, use the Crop tool.

1. Arrange the crop around the image.
2. Make sure that Perspective checkbox is checked in the Control panel.
3. Click-and-drag the cropping box corners and move them to the corract corners in the image.
4. Press Enter to complete the crop. The image is stretched to the correct right angles.

Cropping

• The Crop tool can also be used to rotate. Move your mouse just past the crop box corners to access the rotation feature.
• Remember that if an image is to be used as a bleed, don't crop too tightly; give yourself a ¼" margin along bleed edges.
• If you don't want to permanently remove the pixel data for the cropped areas, hide them:
  • Convert the Background layer to a regular layer by dragging the little lock icon on the layer to the trash can at the bottom of the Layers panel.
  • Draw your crop box.
  • Choose Hide in the Control panel.
  • Press Enter to complete the crop.

• You can resample (resize) the resulting crop:
  • Select the Crop tool.
  • Select the desired height and width in the Control panel prior to drawing the crop box.
  • Draw your crop box.
  • Press Enter to complete the crop.

Changing Resolution

You can change image resolution using Image > Image Size.

Decreasing

• Decrease resolution to whole integers of the original resolution (reduce to half, a third, a fourth, etc.)
• Use Bicubic resampling.

Increasing

• When you increase an image's resolution, the computer must guess how the pixels that will be added will look. This is called interpolation and it involved complex algorithms.
• Plugins for Photoshop such as Perfect Resize specialize in quality results from interpolation.
• Sometimes you can achieve better results using stepwise interpolation: increase the resolution by a small percentage at a time.

Fixing Color Casts

• You can determine whether an image has a color cast (an unnatural tint in one region of the visual spectrum) using the following technique:
  1. Open the image in Photoshop.
  2. Window > Histogram
  3. From the panel menu, select All Channels View
  4. If all three colors fill out the whole tonal scale in a uniform way, the grays are balanced. If not, you may have a color cast.

• There are a number of ways to fix color casts, including:
  • Image > Auto Color
  • Image > Adjustments > Variations
  • Image > Adjustments > Levels, then adjust each channel's histogram individually

In the photo above, there are plenty of reds in the brighter areas, but no blues or greens. This results in a photo with a red color cast.
The result of using Auto Color alone. There are now few colors in the bright range.
The result of manually adjusting the image using Variations.
The result of adjusting the histogram for each channel in Levels.

Levels, Brightness and Contrast

Homogenizing Images

Sharpening

Image Retouching

Activity: Jigsaw Reading

Each student will be assigned read one of the following segments in the textbook in class. Then each will share the main idea and several keypoints with the rest of the class.
When sharing out, please summarize rather than reading directly from the text.

• Making Selections
• Quick Mask, Pixel and Vector Masks
• Clone Stamp and Healing Tools
• Blur, Sharpen and Smudge
• Dodge, Burn and Smudge
• Brush and Pencil
• Match Color

File Naming and Meta Data

Week 2: Chromatics

Week 2: Chromatics

Assignment

Complete the tutorials described within the lecture topics below.

Portal

Upload the following to Week 2 Lesson:

Week	Class Dates	Topic	Assignment Summary	File Name	Points	Due Date
2	10/11/2016	Chromatics	Duotone	duotone.psd	10	10/18/2016
				duotone.pdf	5
			Tritone	tritone.psd	10
				tritone.pdf	5
			Gamut Adjusted	gamut-adjusted.psd	10
			Spot Color	spot-colot.psd	10

Student Showcase

We will take a look at any of your new work which is ready to share.
For the business card project, we will discuss the following aspects:

• Overall strength of the design
• Degree to which:
  • the file is press-ready
  • the design meets the needs of the client

The Physiology of Color

Lesson 02: The Computer

Lesson 03: Color Management

chromatics

noun. the science of color

Color Terminology

Color Models

CMYK stands for Cyan, Magenta, Yellow and Key color (which is black). CMYK is the color model used for printing presses. It is based on the chemistry of mixing translucent printing inks rather than paint. It is called subtractive because if you mix the three primary colors (cyan, magenta and yellow) together, you get black rather than white (in theory; in reality you need to added pure black ink to get real black.)
RGB stands for Red, Green, Blue. It is based on the way the light mixes on a computer screen. It is called an additive color model because if you add the three primaries (red, green and blue) together, you get pure white light.

Gamut

A gamut is a range of colors that a particular device can reproduce. For example, CMYK can produce fewer colors than can be found in the RGB color model. Any color in RGB that cannot be reproduced on a given device in CMYK is consider "out of gamut."

Hue, Chroma, and Value

• Hue (AKA color)
  Distinguishes colors by what we would typically mean by the word "color." For example, green, purple, orange.
• Saturation (AKA chroma, depth, intensity, purity)
  Distinguishes color by the richness or brightness. One one end, you have pure color; on the other, you have gray.
• Value (AKA tone, lightness, shade)
  Distinguishes color by the lightness or darkness. One one end, you have a color near white; on the other, you have that color near black.

Hue	Saturation	Value

Warm, Cool, and Neutral

• Warm
  Red, orange and yellow are warm and visually tend to jump forward into prominence in a piece of design.
• Cool
  The cooler hues — green, blue, and purple — tend to recede in a design.
• Neutral
  A neutral a pure gray or the combination of complementary colors. Complementary colors are those that sit opposite each other on the color wheel. Neutrals are more natural colors and tend to be brownish. Sometimes, neutras are described by how warm or cool they seem.

Warm	Cool	Neutral

Spot and Process Color

Process Color

Dot patterns of cyan, magenta, yellow, and black ink are overlaid to simulate the desired hues.

Spot Color

Spot color requires blending different inks into one ink resulting in the required hue. This method resembles blending paints for household use.

Building Color with Spot Colors

You can create the illusion of many different colors using only two colors of ink printed as various screen values and overlapping each other. Using two colors in a print run is less expensive than using four colors as in process color.
The most common combination is black plus one other color. This is often referred to as a duotone.
Duotone

original RGB image

Rubine Red plate

black plate

duotone with black and Rubine Red

Activity: Create a Duotone in Photoshop

Let's try creating an attractive duotone image in Photoshop which rivals the appeal of a full-color image.

1. Locate a full-color, high-resolution photograph online or from your own image files.
2. Open the image in Photoshop and save it in Photoshop format as duotone.psd.
   
3. Image > Mode > Grayscale (discard the color information)
   
4. Image > Mode > Duotone...
5. Type: Duotone
6. Click on the large white square for Ink 2.
7. Select a Pantone color and view the preview in the main image window.
   
8. Click on the Duotone Curve square (white square with diagonal line) for each color to adjust how the color affects the overall image.
   

Sample duotone settings

6. To send the file to press, you create a PDF which has a separate image for each ink plate. Here's how:
   1. File > Print
   2. Printer: Adobe PDF
   3. Color Handling: Separations
   4. If necessary, rotate the orientation and check "Scale to Fit Media".
   5. Click Print.
   6. Save the PDF as duotone.pdf.
   7. Open up the PDF when it is done and view the separations. They will be in the same order as your ink colors in the Duotone Options dialog box.
7. Now try a tritone for a different original image (Hint: select the tritone type from the Duotone Options dialog box.) Name the file tritone.psd.

original
grayscale
duotone based on previous settings
tritone

8. Make a PDF with separations for this file and save it as tritone.pdf.

Color Spaces

• We use color models to describe the colors of digital images. 
• Color models include RGB, CMYK, Lab, etc., and each of them uses a different way of describing colors.
• In the various color models, there are color options known as color spaces. For instance, RGB, contains sRGB, Adobe RGB, Apple RGB, etc.
• Each color space has a limited range of reproducible colors, known as gamut. 
• Various electronic devices work within their own limited color gamut. Not one of them can reproduce the total range of colors seen by the human eye.
• When using Photoshop (or other image-producing software), image color values are actually being adjusting numerically.
• These numerical values have a very localized color meaning in the color space (gamut) of the device that is reproducing the color.
• Whenever your image is moved from one device space to another device with a different color space (i.e., scanner -> monitor -> printer), which can only reproduce colors in its gamut, the image colors will change.
• For example, pretty blue on screen may end up as dark purple in print.
• The color change happens because each device has mathematically interpreted the RGB or CMYK values according to its own color space (gamut).
• Because each device has a different color space, it’s impossible for all the colors you see on your monitor (RGB color space) to match the output from your desktop printer (CMYK color space).
• While color monitors are only capable of displaying certain parts of the visible color spectrum, color dye pigments used in the printing process are capable of reproducing even fewer of those colors.
• Some of the colors produced by inks cannot be displayed on a monitor, and some colors displayed on a monitor are not reproducible using inks on paper.
• Different monitors can display the same image very differently.

Adjusting the Color Space in Photoshop

Even though it’s impossible to match all colors on all devices, using a color management system is one good way to help achieve something close to consistent and predictable color between devices.  Luckily Photoshop has a very good color management system built into it.
Changing Your Photoshop Work Space Color Settings

Gamut Warning

Photoshop automatically brings all colors into gamut when you convert an RGB image to CMYK. Some detail in the image may be lost when this happens, depending on your conversion options.
You can identify the out-of-gamut colors in an image and correct them manually before converting to CMYK. You can use the Gamut Warning command to highlight out-of-gamut colors (View > Gamut Warning).

original image

viewing Gamut Warning in Photoshop
Here's how to make a manual adjustment to the out-of-gamut colors so that you have control rather than leave it "in the hands" of Photoshop:

1. Find a high-resolution image with a wide range of colors. Open it in Photoshop as save it as gamut-adjusted.psd.
2. Turn on the Gamut Warning (View > Gamut Warning).
3. Take note of the hues in your image that are out of gamut. In the image above, they are mainly yellows, reds, and greens.
4. At the bottom of the Layers panel (Window > Layers), click on the Create new fill or adjustment layer icon and select Hue/Saturation.
5. In the Adjustments panel that appears, look for the dropdown that says Master. From this dropdown, select one of the color ranges that is out of gamut. I will start with the yellows.
6. The eyedropper tools appear in the Adjustments panel.

7. Select the Add to sample eyedropper (the one with the plus sign.) Click and drag over the problem areas for your chosen color range. Note how the color range at the bottom of window adjusts as you add more colors to the color range for adjustment. Be sure to stay on the gamut warning color, you do not want to desaturate other colors in the image.
8. Once you are have the problem colors selected, drag the Saturation slider to the left, a little at a time, to bring the color into gamut.  Watch the gamut warning color closely as it disappears. Use the smallest possible slider value. You do not want to over-desaturate the colors.

9. Repeat steps 6-8 for the other color ranges which are out-of-gamut.
10. Save your adjusted file.

Below, I have fixed the reds and greens as well.

Roll over the image below to see before-and-after:

Creating Spot-Color Images in Photoshop

We already looked at desaturating a full-color image and creating a duotone. Here's how to have greater control over where spot colors are placed. This technique works best with simple graphics like line art.

1. Find a high-resolution line-art image in Google Images (hint: when you see your search results, select Large and Line Art from the left-hand options menu.) Select something with enclosed spaces that can be filled with color, and keep it simple.
2. Open the file in Photoshop and save it as spot- color.psd.

3. Image > Mode > Grayscale
4. Open the Channels panel, where you will see a single Gray channel.
5. From the panel's menu (upper-right corner), select New Spot Channel...
6. Click on the color swatch to select a color.
7. In the Select Spot Color color picker, click on the Color Libraries button.
8. Select a Pantone color (remember what number it was!) and click okay.
9. Name the spot color channel according to the color you chose (e.g. Pantone 186 C).
10. Set your foreground color to black.
11. Select the Gray channel.
12. Using the Magic Wand tool, click in an enclosed area of the image.
13. Hold the Shift key down and click in each of the remaining enclosed areas.
14. Select > Modify > Expand...
15. Expand By: 2 Pixels, click OK.

16. Select the Pantone channel.
17. Alt+Backspace to fill the selection with black. It will appear in the image thumbnail in the Channels panel as black, but as your selected Pantone color in the image window.

18. Ctrl+D to deselect.
19. You may need to zoom in see tiny details that were missed. Just paint daubs of black with a small, 100% hardness paintbrush on the Pantone channel.

When you are done, you will have two channels, each of which can be printed as a separate plate. One would be a black plate and the other plate would be printed with the color ink of your choosing.

You can turn off the visibility of the Gray channel to see how the colored plate would look on its own.

To change the ink color, simply double-click on the image thumbnail for the Pantone channel. Then click on the color swatch to change the Pantone color and click OK. The channel name should automatically change to reflect the new color.