Image comparison
Lay two pictures of the same scene on top of each other with a divider students drag across, so the difference shows up exactly where it is.
When to use it
Image comparison suits any pair of pictures of the same place or object: before and after, then and now, a diagram with and without its labels, or two proposals for the same street. Moving the divider back and forth shows differences that are easy to miss when the pictures sit side by side.
Setting it up
In a worksheet, use the + between two items and choose Image comparison.
Click the pencil. Add the first picture: drop a file onto the slot, browse for one, or add it from an image URL. The second slot opens once the first has a picture.
Under each picture, write a short Label. It is shown on that side of the comparison.
Choose the Divider direction. Horizontal puts the pictures left and right; Vertical puts them top and bottom.
Set the Starting position, in per cent, to decide where the divider stands when students first see it.
Click the tick.
Only the first two pictures are used. If the pictures have different shapes, the second is cropped to fit the first.
What students do
Students drag the divider, or click anywhere on the picture to move it there, and stop at whatever detail they want to look at. With the keyboard, the arrow keys move the divider in small steps, and Home and End take it to either edge.
There is nothing to answer, and nothing is recorded.
Tips
Use pictures with the same framing and size. The comparison works only if the same point sits in the same place in both.
Set the starting position so that students first see the side you want them to start from.
Give students something to look for, for example who has room on the street in each version.
Keep labels short, such as "1990" and "2020" or "Before" and "After".