I think there are a lot of parallels between the world of photography and that of the world of painting.
I found this video today on YouTube which I felt has just as much validity in teaching us photographers something, as well as it's intended audience of painters.
The video deals with the art work of Winifred Nicholson. She was a beautiful painter of still life's that she painted from inside looking out. I've enjoyed her work for many years since I first found out about her while on the Isle of Eigg here in Scotland. Winifred visited the island several times and made many paintings whilst there.
Anyway, I digress a little. In this video we see that Winifred was very clever in allowing us to know that she was painting from inside a house looking out, but manages to avoid showing us the window. But more interestingly, as she developed her style, she started to incorporate the inside of the house into her paintings, but she did so by managing to make the inside feel 'related' to the outside. She did this by clever use of tonal relationships.
In her earlier work, the quality of light within the house is different from that of outside - thus creating a divide. As viewers, we do not feel so connected with the outside. Whereas in her later work, she was clever in making the quality of light and tonal responses inside and out similar, therefore relating the two, and ultimately bringing the outside into our viewing space.
I've been thinking about tonal relationships for a long while in my own work, and I find that when I make two objects in the same frame tonally similar - they become highly related. Conversely, when I make two objects in the same frame tonally dissimilar, they become less related.
Well, this video illustrates this point very neatly, particularly in the last image where we see that Winifred uses a couch inside the home as context - something for us to begin from, and then through the similarity of light and tone inside and out of the house, invites us to reach outside the house where the outside feels like an extension of the inside.
Although it's discussing paintings, I think there is always much to be learned about photography through the world of painting. I hope you get something from this short video.