Scale

The lightness or darkness of a color or a tonal value is relative to another. Big is relative to small, but also relative to the environment. Scale is used in plans and maps to represent measurements in proportion, but is not absolutely necessary. What is most important is the juxtaposition, what is next to the object that we can recognize its size often relative to us, relative to our body.

For that reason, the designer must be aware of the relationships between parts when communicating information through an image. What is the scale, what should the user recognize as the real size of a shape or object? Often this aspect is overlooked and many designers use several variables in the same image giving redundant information. The following examples will clarify the point:

OpenDX: Earth's Terrain
This map records land height and ocean depth. The scale-bar gives us information on colors assigned to a specific height, we see different values of blue in which darker is deeper, a high saturated blue is sea level but lighter blue has not been assigned to the scale, it is present in the map and it doesn't have a value. The lighter blue is used to enhance the look of the image, but the its presence affects the scale. Aside from color we have a three dimensional representation of the same information. Although is an attractive image, is very difficult to read. The height and depth of the earth is out of scale in relationship to the area and size of the globe.

British Museum
This is an orientation diagram of the British Library in King Cross. The diagram simplifies complex spaces to help the reader create a mental model of the building and to recognize the areas accessible to them. The low saturation of the colors help the user understand the information. The position size and proportion of the areas also clarify their location relative to each other. The only problematic issue is the use of the human diagram to indicate where the bathrooms are. When a comparison is made between the human figure and the diagram of the stairs, the understanding of the image comes into question.