Posts Tagged ‘DOF’
The human eye is a fascinating instrument. It is a fast, superbly versatile light machine we have at our disposal from birth and although it only sees in visible light, its design remains an unequalled achievement many an optical instrument designer would like to come close to
A camera is an incredible toy that can force limitations that the human eye can’t generate, mostly because the brain takes over. The human eye and brain are designed to provide the best vision for us to survive. Also, it has an incredible depth of field: we see things in focus, whether close or far. This is partly due to the fact that the eye “refocuses” extremely fast, but also because it has a good aperture and f numbers varying between f/8.3 and f/2.1 (although a lots of research is going into that too!) This is to not lose sight of the far if we’re focused on the close. Again, a very effective survival strategy.
But when it comes to photography (or aesthetics, or eye-candy, however you want to call it), a shallow depth of field can be a delight. It can focus your attention on something simply by putting everything else out of focus. This is great for portraits, or macros. You can play a game of tones and impressions. You can become a modern-day impressionist.
The brain is also trained to interpret photography. This is why tilt-shift photography is so much fun. If it has a shallow depth of field, i.e. a shallow slice of sharp, in-focus subjects, it gets interpreted as macro, which is why a landscape manipulated to look like it has a shallow DOF, we see as a miniature of the landscape, like being in Legoland or Madurodam.
Leiden, the Netherlands
My friend Doug and I played a little game at the week-end. We were walking through the botanical garden (a heaven for photographers) and I was shooting about 3 photos a second like I always do. I was showing Doug where I like to hang out with my camera and play with lights, plants and waters, and he spotted a really cool reflection of the striped ceiling against the water. Something to take a picture of.
At first I tried with whatever settings I had on the camera (shallow DOF!) and could not get anything at all. I could focus on the plant but wouldn’t see the cool reflections:
Then I focused on the reflections and couldn’t see the plant. Nor could I see the distortion in the reflected stripes.
I figured that the reflection was at a comparable distance to the ceiling, and that the plant being that close to the camera, I had to increase my DOF as much as I could to get both, and that’s when I finally got what we could see:
What a relief! I could capture what the eye could see.
But beyond that photographic game, I wonder why the shallow DOF shot of the reflected stripey roof kept looking straight. No distortion, nor a loss of the lines. I would have expected to see the lines blur where the distortion occurs because the lines would get out of the focal plane, but no. The lines just continue straight.
I guess I’ve got to think a little more about this whole thing to understand exactly what’s going on. I believe it has to do with the eye extrapolating the origin of light in straight lines but I’m not sure exactly how it happens in this case. Anyone who has a suggestion, feel free to drop me a comment, thanks!