Framing your subject within a geometric frame adds another dimension to your images.
I take it for granted that photographers and painters look for frames within the frame (or canvas). I look for this type of image in the streets more than I'm aware of, subconsciously, based on the number of recent examples in my archive.
What's appealing about this for me is that it creates an exaggerated or virtual foreground that renders a subject as more interesting. You can bet I wouldn't have bothered photographing this woman (pictured above), same pose, on the street, had she not been siting in a car or otherwise positioned within another frame. Without an interesting background or for lack of a compelling foreground, people in and of themselves can be unworthy of capturing otherwise, at least within the framework of street photography.
And I don't even believe that a frame within a frame subject need be perfectly framed. Referring back to the woman in the car, I didn't choose to frame the entire natural framework provided by the window. I felt knowing she was in a car was good enough. Plus, I wanted to crop in closer to her to capture the essence of this candid moment better.
Contrast this method with the above, where in the camera frame everything is captured, including the subject's frame (window). What we choose to see utilizing both frames, is a compositional decision which should be made purposefully, every time. Had I cropped in on the above image, I think I would have lost the entire charm of the rickshawala in his auto. I didn't capture the entire vehicle - which was intentional of my part because I chose to ignore what I thought was not vital information to include visually. It's this kind of thing which ultimately sets we visual artists apart, I believe, among other seemingly small but vital decisions to be made in a given image.
The above image is another example of adding interest. Merely photographing someone from the shoulders up out on the streets isn't typically going to be interesting or insightful. But capturing this rickshawala not only (and hopefully!) adds more interest, but it's also informative, in that we know that the photographer was sitting behind the driver as passenger, that they're seemingly stuck in traffic. Which we were.
In the above image, there's a multitude of things in the foreground before we even arrive at the subject, the man in the midground. There are literally two frames within a frame in this image, the window where you see my reflection, and then the small window framing the man's head and shoulders.
A similar image to the previous example - two frames within a frame.
This doesn't only apply to street photography. A frame within a frame effect can be achieved within a studio. The subject's frame doesn't have to be made up of right angles either. A balloon could serve just as well.
Another example of multiple frames.
There are so many opportunities for images like these if you shoot street photography. I would think that even in small towns, where maybe there's not as much happening, shots like these could help add interest when subjects are limited in supply. That is, if you're fast enough, discreet enough, and at the same time, bold enough, to get shoot these type of images.
Ultimately, I think that shooting frames within frames adds a dimension of candidness and intimacy which may not have been achievable in other situations. Portraits are great. But thinking in terms of frame within a frame will help create images which stand apart. They should be sought out whenever the opportunity presents itself. Because what this achieves, almost as an unspoken afterthought, is a sense that the photographer took his or her time with the shot. It was more planned, regardless of actual shooting conditions. It could even lend a more artistic feel to the overall image. This is how I see it, anyway; framing up within a frame creates an artistic perspective where none could otherwise have not existed or been possible. Therefore, it's imperative to capture such moments before they vanish forever in the next blink of an eye.