"The photographs which the man brought showing bridges and cities, trains, boats, big buildings, were not impressive to us...Having had no experience with the diminished scale of things in a photograph, we gained no magnitude." Does this sentence say that the people were not impressed by the building because in the photograph they are small so they do not know what they really are like.

Yes.

yeah

oh ok thank-you

Yes, you have correctly understood the meaning of the sentence. The sentence suggests that the people were not impressed by the buildings because they were not familiar with the concept of a diminished scale in photographs. When the man showed them photographs of bridges, cities, trains, boats, and big buildings, they were not able to appreciate the magnitude or true scale of these structures. Since they didn't have any prior experience with viewing things in photographs, they couldn't comprehend the actual size or grandeur of the buildings and therefore were not impressed by them.