July 14th, 2015

Students will learn to use the calipers, virtual props, and ratio tools in the Size Wise app to create forced perspective photographs while noticing and using ratios in the process.

Activity 1: Quick Intro: Virtual Giraffe Challenge

Image Size Ratios


Expected Activity Time

Intro to Topic and App (10 minutes)

Virtual Giraffe Challenge (20 minutes)

Sharing and Discussion (10 minutes)

Materials and Prep

  • Size Wise Quick Intro: Virtual Giraffe Student Sheets
  • 1 iPad with Size Wise app
  • Wifi access to send work to other iPads or to online project space
  • Measuring tapes
  • Prep: Give yourself ample space for students to move along distances. Taking turns in the hallways can work or going outside can work nicely.


Activity Prompt

Intro: Have you ever seen those funny photographs where things look wildly larger or smaller than they really are?  Display examples like those found on the blog: www.hongkiat.com/blog/force-perspective-photos

In this activity, you will create some forced perspective photographs by taking pictures of you and your friends posing with a virtual giraffe in the Size Wise app.

The Giraffe Challenge: Pose with the giraffe in three photos so you are:

  • As big as the giraffe and can tickle his chin,
  • Three-fourths the size of the giraffe,
  • One-third the size of the giraffe.

Which picture is the funniest? Use ratio language to describe the composition of your shots.

To Do:


Virtual Giraffe Challenge (20 minutes):

Have students:

  • Open the app, and select “Take Some Pics.”
  • Create an image size caliper by tapping on “Calipers” and then tapping “Image Size Caliper”
  • Measure friend with the Caliper from head to toe.
  • Browse “Virtual Props” and select the giraffe.
  • Start taking your photos with the Giraffe.
  • Work together to take a picture with the subject appearing to be the same height as the Giraffe (1:1 ratio).
  • Tap the “Ratio” tool and examine the data. Ask:  What is the ratio?  What does this mean?
  • Take two more pictures where the subject is:
    • 3/4 the size of the giraffe
    • 1/2 the size of the giraffe
  • Use the Ratio and Data tools to look at the data. Ask: Do you see any patterns?


Prompt students to describe the photos that they took and what they had to do to achieve certain shots. Encourage students to think about how many times larger or smaller an object is in relation to another.  Have students discuss which ratios get the best or most satisfying effects (e.g., why does setting up your subject in a 1:1 ratio with the giraffe look funny)?

Ask students:

  • How many times larger/smaller is one object than another?
  • How would you describe this as a ratio?

Language and discourse to listen for:

  • 25% the size of ________
  • Three times larger than ________
  • It is in a ____ to _____ ratio

Extensions and Inquiring Further

Giraffes on average are 15 to 18 feet tall.  You can extend this activity by having students compose a realistic shot of themselves standing next to an average height giraffe.  They will need the ratio and caliper tools and real-world data about giraffe heights.  If they were standing next to a real giraffe, what would the ratio of the student’s height to the giraffe’s height be? What would they look like standing next to one another?  For example, if a student is 5 feet tall, a 15-foot giraffe is 3 times as tall as she is.  The image size ratio of student to giraffe is 1:3.  A link to other interesting “Size” issues with giraffes can be found here:


This can also be done with other virtual props with known sizes in our prop library.

Virtual Giraffe Challenge

Move back in forth in space to pose with a virtual giraffe so that you appear to be different heights.

  1. Add a new caliper with your actual height.
  2. Go to “Virtual Props “and choose the giraffe
  3. Tap the “Distance” tool as well as “Ratios ” and snap the following three pictures:
  • Your image size is in a 1:1 ratio with the giraffe
  • Your image size is in a 3:4 ratio with the giraffe
  • Your image size is in a 1:2 with the giraffe
  1.  In the Gallery, tap “Data” and drag in the three pictures you took and compare.

Size Wise Quick Intro Activity: Virtual Giraffe

Reflection Questions:

  1. Try this challenge again with another virtual object such as the soda can, statue of liberty, etc. (NOTE: If you choose a SMALL virtual object, shoot for ratios of: 1:1, 2:1 and 4:1.) Which ratios produced the most amusing effects?  The most realistic effects?  Why do you think that is?
  1. In the Gallery, tap “Data” and look across the data of your pictures. Observe the way your image changed sizes between the photos. Think about and express the mathematical relationships you see.
In Camera Mode, you will use:
 SW1.2 To enter and calibrate the height of themselves and their friends
 SW1.3 To see how the image size of their subject relates to the image size of the virtual
 SW1.4 To reflect on the things they notice about the pictures they take. They can email
these notes to themselves.
In Gallery Mode, you can use:
 SW1.5 Compare data across 4 photos (e.g., note the image size in each of the photos)
 SW1.6 Write ratios that they see on the photos they took.

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Big Idea

In this activity, students learn about some of Size Wise’s core tools while exploring how ratios can describe the relative image sizes of their subjects in a photograph and how that affects the composition of their shots. Using the ratio tool, students can use ratios to make some deliberate choices of how things appear on the screen.
Students will also begin to play with creating forced perspective photography- where things seem wildly larger or smaller than they are in real life. By deliberately manipulating their distance from the camera to change how large or small they appear next to a virtual giraffe, students should notice that there is a relationship between image size and distance from the camera. This activity lays the groundwork for the proportional relationships they will explore in more complex projects later on.
NOTE: The core concept is that of ratios between the onscreen images of the giraffe and the student.  In this activity, the goal is simply for the students to notice that they can manipulate their image size by moving back and forth in front of the camera.

Learning Objectives

Students will use ratios to solve real problems that pertain to ratios and proportions in the field of digital photography.

From this activity, students will be able to:

  • Use ratios to represent the relationship between two quantities.
  • Follow a multi-step procedure when performing technical tasks.

Standards Addressed

Common Core State Standards-Math  

Ratios and Proportional Relationships

6.RP.A.1. Understand the concept of a ratio and use ratio language to describe a ratio relationship between two quantities.

Common Core State Standards-Math  

Mathematical Practices

MP2 Reason abstractly and quantitatively.

MP4 Model with mathematics.

Common Core State Standards-ELA  


RST.6-8.3. Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.



  • Image Size Ratios
  • Calipers
  • Object Distance
  • Forced Perspective Photography

Device Strategies

Single-Device implementation

Take various volunteers to the front of your classroom to pose with the giraffe.  Direct a student to stand where the size of her image is in a 1:1 ratio with the size of the giraffe’s image. Have students speculate where they think she would have to stand to be in a 1:2 or 1:3 ratio.  Have students discuss how they might figure out height of the objects. Share examples via your smart board or projector and discuss what children can notice about how knowing one quantity helps you solve for another.


Multiple-Device implementation

Because this activity requires collaboration, this is a perfect activity for 2-4 students.  Have students take turns being the model and the photographer.  This can lead to interesting data investigations that have to do with the differing heights of the students in the group.

Tips & Ideas

Discussions of why certain shots are funny allow students to share their underlying understandings of scale and proportion in the real world.  Making these connections can help reinforce some of the proportional reasoning introduced in this activity.