I'll open with this image, obtained while I was doing a study on the water-air interface and its geometry. This was conducted in order to get a better understanding of what is known as "flashing" in underwater light measurements. The "flashing" itself is rapid oscillations of high- vs low-intensity light, the intensity of which can surpass that of the incident sunlight several times. The casual observer can observe it as a pattern of bright ripples across the bottom of a swimming-pool or floor of a shall lake.
I did this by using the water film itself as a refractive interface and placed a light-sensitive paper 10 cm below the surface. In practice I went to the nearby river, unfortunately at that time in violent spate, at the darkest time of the night, around 0230 (late summer), bravely waded the river until I had water chest high, then exposed in sequence the sheets of paper in my 8x10" film holder using a SB-24 flash as light source. Had to hold the flash in my mouth because the hands were occupied with the film holder and the photosensitive medium. Then, after exposing my two sheets, back to my home where I temporarily arranged my bath to become a dark-room. Took me a couple of nights to get acceptable quality and overall it was a very cold and wet experience. Which I wouldn't have been without.
The photo paper was b/w, but I found the images were easier to interpret if they were tinted, so added a "water blue" to them.
By the way, the interface pattern is fractal and in the processing, I ended up with a jpg that grew exponentially lest I added some blur to the original scan.
