Sight Size is an app for the visual comparison of images. The app makes it possible to transparently view two images at the same time, and also to adjust the images so that they can be seen in the same scale. This is similar to viewing the images on a traditional light table.
The app is intended as a learning tool when drawing or painting. Then the first image would be an image of the object being drawn (for example, a face or a landscape), and the second image would be an image of the drawing (drawn with pen and paper). By seeing both images transparently over each other and at the same scale, one can see where the drawing is off, and which parts need to be corrected. This is not always easy to see otherwise.
The name Sight Size comes from a classical method of drawing where the subject and the drawing are placed so that from a fixed vantage point, they the can be compared at the same scale.
After a image has been selected in both the subject and overlay tabs, the images can compared after tapping the image in the overlay screen. Then the following controls are available:
Slider: Adjust transparency of images.
Lock/Unlock: Locks images so they can be panned and zoomed either independently or locked together.