PHLEARN PROCESSING TECHNIQUE SUBMISSION
This is a technique I sometimes use for lighting dark environments using a single static light source across multiple exposures and then using layers and blending techniques in PhotoShop to create a single well lit final image from these multiple exposures. In this instance I was shooting the pitch black interior of an early jet engine testing tunnel. The final image is shown here but when I first tried to shoot it (second image) I encountered several issues I wanted to overcome. I like to back-light subjects like this as it brings out the textures in the tunnels walls but having the light source in the image and facing the camera was creating a star burst effect that didn't really want in the final image. Secondly I didn't like the fact that walls closest to the light were too bright and the walls furthest from the light (by the camera) were almost totally black.
You can see my first attempt below. The fall off in light is caused by the Inverse Square Law of Light. Which states 'The intensity of a point light source is inversely proportional to the square of the distance between the light and the surface. Meaning at 1m the intensity of the light would be X, at 2m the intensity would be 4 times less intense than at 1m because 2 squared is 4, at 3m the light would be 9 times less intense and so on.
I wanted to think of a way I could re-shoot the tunnel using back-lighting whilst overcoming the inverse square law of light but also hiding the light source from the camera.
When I returned I found a section of pipe outside the tunnel and brought it inside and used it to lift the light source off of the floor (although I could have used a second tripod for this too). I placed the camera on a tripod in a slightly different off centred position and placed the light on the pipe close to the camera (top left of the below images), after capturing a shot of this light position I walked the pipe six paces further back along the tunnel (top middle image), I repeated this technique until the light source was placed on the jet nozzle at the far end of the tunnel where it was in my first unsuccessful attempt. But, the star burst effect from the light was still visible in each of these first 4 shots. So I captured one more image where I turned the light source around to face down the tunnel illuminating the jet nozzle at the far end. When I got back home I stacked the 5 shots in layers, with the closest light position at the top of the stack to the shot where the light was illuminating the end of the tunnel at the bottom. It was then a simple task to remove the dark area behind the light flare from each layer and to allow the detail from the next layer down to show through. Blending in the final where the light flare wasn't present removed any trace of the light source. The final image also does not suffer from the excessive light fall off experienced in my first attempt. It's actually a fairly easy technique to do with only a basic knowledge of using layers in Photoshop required.
Hope you have enjoyed this technique and will maybe give it a go too.