That is why we include few scaling elements like cars, people, etc. in the corner of the frame as a part of the main subject while shooting huge architecture, buildings, landscapes, machinery etc. Again that is the reason why tiny objects are shown on the tip of a finger for comparative sizes. In any case, a photograph mostly cannot tell you about the ‘real size’ of any subject.
The size of the subject as shown in a photograph is always a point of importance. The size of the subject in photography means its ‘visual size!’ Well, the visual size of the subject in an image can be modified by several ways. The easiest being, moving closer to make it look big and moving away to make it look small. I have always wondered how a huge ‘Boeing 747 Air Bus’ diminishes in size and vanishes in to the sky as it flies high.
When I was in my primary school, I used to wonder as how the entire football ground with our high school players disappeared as I bring my little finger closer to my eye. The small finger which is closer to my eye grows bigger in size than the foot ball ground which is away from my eye. Here the visual size has something to do with the distance.
In photography the relative subject sizes (visual size) in an image can easily be changed by using lenses with different focal lengths and shooting from different distances.
In all the cases, the subjects’ size as shown is not true to life. In the sense they always confuse the real size! Surprisingly, hardly we could guess the actual size of any subject from a photograph…!
“There are no rules for good photographs, there are only good photographs.”- Ansel Adams