Archived copy for reference only


Graphic Design / Interactive Design / Fine & Applied Arts / Parkland College

Graphic Design Exercises
Photoshop: Pixels & Resolution

(Archived from 2019)


To understand the relationship between pixel dimensions and file sizes of Photoshop files. To learn Photoshop production and colorizing techniques by example.

Download starter files


Scanned continuous tone images can take up a lot of hard drive space. But if your image doesn't have enough pixels (data), the result will be poor print quality. The ideal situation is an image that's just the right size for the intended print job. Here are some general guidelines:

  • Scanned images can NOT be blown up without losing quality. Scan large, then size down to the size you need. Overestimate if you're not sure of the final size.
  • You need about twice as many pixels as halftone dots. This means a halftone dot that is 150 lines per inch needs 300 pixels per inch.

Halftone dot size is determined by paper quality and the method of reproduction:

  • Photocopies will print fine at 60 lines/inch
  • Newspaper is 85 to 100 lines/inch
  • Business-quality offset printers use paper plates which require 100 lines/inch
  • Commercial printers use metal plates which can reproduce 133 to 175 lines/inch

In general, designers have standardized scanning to three resolutions:

  • 300 PPI for commerical print jobs
  • 150 PPI for newspaper, presentations (photocopies, laser printers)
  • 75 PPI for web and screens

open the file "original.jpg" and save it in native PSD format at the following sizes (use appropriate folders and file names):

  1. 300 PPI 13x8 inches
  2. 300 PPI 8x5 inches
  3. 150 PPI 8x5 inches
  4. 72 PPI 6x4 inches

open each PSD file and save it as JPEG (quality=maximum):

  1. 300 PPI 13x8 inches
  2. 300 PPI 8x5 inches
  3. 150 PPI 8x5 inches

open the 72 PPI PSD file and save it for web in the following formats:

  1. 72 PPI 6x4 inches in JPEG high
  2. 72 PPI 6x4 inches in JPEG medium
  3. 72 PPI 6x4 inches in JPEG low
  4. 72 PPI 6x4 inches in GIF 64
  5. 72 PPI 6x4 inches in GIF 32
  6. 72 PPI 6x4 inches in GIF 16

dupe the 150 PPI PSD file (opt+drag to "color" folder), then colorize it and save it in the following manner:

  1. image > image mode > duotone: make a monotone with PMS 280, save as EPS
  2. make a duotone with PMS 124, save as EPS
  3. add a yellow spot channel for PMS 109, copy and paste a reverse image of the building into the spot channel, save as DCS 2.0 format (single file with color composite)
  4. image > mode > RGB: add adjustment layer (hue/saturation, colorize=yes); save as layered PSD in RGB mode; save as flattened JPEG in CMYK mode
  5. import above files into InDesign: window > output > separations

in finder, examine file sizes, then make a screenshot of your "pixels" folder.

  1. submit b&w laser proof with your name and the exercise number on it for grading
  2. file your graded proof in your Process Book for individual review

Last updated: 5/7/21