One of the last principles of design to write about is scale. Scale is closely related to proportion except that scale is primarily viewed as a relative standard or measure outside of an object related to some constant unit.
In interior design, scale is sued as a way to compare the size of an object or an interior. The photo is a great example of of how the little girl shows you how large the door really is. If she was not there you might not be able to tell how large of a door that really is.
I just finished building my house and I noticed while in 2D the kitchen and family rooms felt good sized but I was concerned they would be too small.
Until the house was complete and we moved physical items into the house to give the rooms scale, it allowed me to see that the rooms were large enough and maybe could have been designed a little smaller.
Scale is a balancing act and hard to grasp it until the space is in 3D.
Scale can refer to small or diminutive as well as to large /grand size. Models of interiors are made smaller to help designers get a better idea of how the space will look in three dimension before it is built. We use computer modeling tools today which are all drawn is a scale (typically 1/8") to help with the design process.
- Kilmer, Rosemary & Kilmer W. Otie (1992). Designing Interiors. Orlando, FL. Harcourt Brace Jovanovich College Publishers. pp 120