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