Simple answer: don’t follow the instructions in the books, on the Internet, or use the latest feature built into most cameras.
Someone has once again wrote images from a lens that had an appealing 3D-look to them. No need to call them out; they’re one in a long string of folk that have done so. But are they sure it is the optical design of the lens that produces the 3D effect?
I’ve written this before, but I find myself repeating it a lot these days as I fight through myths: our eye/brain connection has a built in cue for distance: detail.
If you can see every individual whisker, the lion is quite close to you! If all you see is a vague lump off in the grass, the lion is not close to you. Detail tells us something is close, fuzziness tells us something is far. This is true whether your eyesight is 20/20 or 20/100 or whatever.
The trend, partly because of smartphones and their small image sensors, is towards huge depth of field. I often get asked how to put everything up through infinity in focus with full frame cameras. Others ask me how to use focus stacking to put everything from one foot away through infinity in focus. I’m reluctant to answer either question because you basically take a 3D subject (reality) and make it even more into a very flat 2D construct (photo on wall). You’re erasing 3D cues if you keep trying to put everything in focus.
3D also works in other ways in our eye/brain. We focus, just like lenses, at only one distance. The difference is that we contract muscles around the cornea to change that focus distance constantly, and we do it unnoticed. Thus, we think we see near to far in focus, but that doesn’t happen in one moment of time, it happens over time. Our brain tricks us into thinking we’re seeing near/far in focus simultaneously, but we’re not.
While you’ll see different variations on the numbers—partly because our eyes also move up, down, left, and right, partly because everyone’s eyesight has variations—at any given moment your best acuity (detail) is in about a 20° arc at the center of your field of view. That’s because retinal cells are densest in the center. You distinctly recognize shapes at out to about a 60° arc. You can see color through perhaps a 120° degree arc, and motion—essentially peripheral vision—through around 180°. But it doesn’t really matter if these are exact numbers. If you hold your eyes steady on a point, your view is just like older lens designs: excellent in the center, not so good as you move towards the extremes.
What most people describe as “3D look” in photographs is really that: limited depth of field targeting a central subject with high acuity, but less acuity as you move outward. Hmm, just like our eye/brain works.
I’ve long been an advocate of not taking important visual cues out of my photos. I leave infinity out of focus (unless it’s the one thing I want you to concentrate on). I work the outer areas of images in lots of ways, including vignetting, to trigger our usual eye/brain response.
