Substitute Teacher Guide • Grade 9 • Unit 2: Understanding Digital Images
Behind the Image: File Types, Resolution & Visual Hierarchy — Day 1 of 2
Today's focus: File Types & Resolution
✅ Before Students Arrive
- Materials needed today:
- File-format sorting cards (JPG/PNG/TIFF use-case scenarios)
- Printed posters/pages for hierarchy annotation
- Highlighters or colored pencils
- Most students keep their class notebook at its usual spot in the room and use it every day (see routine below) -- but it's each student's own notebook, so a few may bring theirs from home instead. Either way, everyone should have one out.
- Write today's Do Now on the board before the bell rings (see below).
📓 Daily Notebook Routine (students already know this)
Keep this going every day, in your class notebook: date today's entry, jot your Do Now response, add any new vocabulary word(s) from today's Key Vocabulary section (word + a quick picture + a simple definition in your own words), and take 60 seconds to sketch something connected to today's topic. This notebook is yours to study from, reference on projects, and pull evidence from later for your portfolio.
🗣️ Opening: Do Now
Write or project this, and have students start immediately:
“What image file types have you heard of before? List as many as you can in 60 seconds.”
📋 Class Plan (step by step)
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Step 1 — 10 min
🗣️ Say: "Today we're looking at ___." Then walk through the point(s) below at the front of the room.
📋 Mini-lesson (10 min): JPG vs. PNG vs. TIFF, and when a designer would pick each.
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Step 2 — 10 min
🗣️ Say: "Today we're looking at ___." Then walk through the point(s) below at the front of the room.
📋 Mini-lesson (10 min): why a poster needs more DPI than a phone screen -- the real numbers designers use are 72 PPI for web and 300 PPI for print.
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Step 3 — 15 min
🗣️ Say: "Here's what we're doing next." Then read the instructions below to the class.
📋 Sorting activity (15 min): match file-format cards to the correct use-case scenario.
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Step 4 — 5 min
🗣️ Say: "Let's hear from a few people before we move on."
📋 Quick share (5 min).
🔑 Vocabulary Introduced Today
- JPG
- A common, smaller image file that compresses (slightly loses quality) to save space -- most everyday photos.
- PNG
- An image file that supports transparent backgrounds and loses no quality; common for web graphics.
- TIFF
- A high-quality, uncompressed file format favored for print and professional photography.
- DPI (Dots Per Inch)
- A measure of print resolution -- higher DPI means a sharper printed image.
✅ Wrap-Up: Exit Ticket
A few minutes before the bell, say: "Time to finish your exit ticket."
“Pick one file format from today and explain, in one sentence, why a designer would choose it over the other two.”
Collect exit tickets (or have students leave them in the usual spot) for the regular teacher to review.
⏳ If You're Short on Time
Protect the Do Now and the Exit Ticket above all else -- those are how the regular teacher tracks daily progress. If a step above is optional/homework, or is a "share out"/discussion step, shorten or skip it first.
⏳ If Students Finish Early
Have them keep working in their notebook: add extra detail to today's vocabulary sketch, review previous vocabulary, or -- if this is a portfolio update week for this class -- work on their portfolio. Early finishers should never be idle or distracting to classmates still working.
📝 For the Regular Teacher (fill in ahead of time)
- Regular teacher's name / how to reach them: ______________________________
- Where finished work / exit tickets go: ______________________________
- Front office extension / emergency contact: ______________________________
- Anything else this class needs to know today: ______________________________