Monday, April 1, 2013

Our Sexy Siren - Shallow Depth of Field

Since becoming addicted to shooting both photos and film, I obsess about many geeky things. For instance, I often think about depth of field (dof). Anyone working extensively with images must consider dof. It is a universal, apparently culture-free truth that shallow dof (where the subject of your shot is in focus and what surrounds it is blurred out) is captivating.  Truly captivating. Hard to look away. In a mind-bendingly paradoxical way, it’s the same idea famously expressed by Supreme Court Justice Potter Stewart to describe his threshold about what pornography is, and what separates it from art, “I know it when I see it”!

The same is true for a shallow depth of field. We know it when we see it! Most people, who aren’t visual image addicts like everyone reading this presumably is, don’t even know what crushed dof is and yet they instinctively love it. Humans respond in a visceral way. We can’t say why crushed dof is beautiful to behold, it just is! Camera lenses are coveted and priced for lower apertures which not only let in more light but crush the dof.

We seem instinctively know “beauty” when we see it. That response has got to be neurologically hard-wired. But why? What would the possible basis for this innate love of crushed dof be?

The other night as I was putting away laundry in my daughter’s room I glanced at an episode of CSI on her television. I noticed how virtually every shot was tailored to crush dof, and how I was correspondingly mesmerized. I couldn’t pull myself away from the screen and watched the whole dang show when I had far better things to do. Why waste my time like that? It wasn’t just the crime story (although that helps and the lighting was fantastic too), but I was almost hypnotized by the way it was shot. “Sexy dof got me again, I thought. Then it dawned on me why… the camera was doing the all the work for me! I didn’t even have to operate my eyes.

When we move through our environment, we have natural and frequent dof shifts. What we want to focus on we do, and the rest blurred out until we shift our focus point. What is out of our focus is always blurred. Selective focus is our natural state in a 3D world. The camera work on CSI both mimicked this natural state AND was saving me the work of choosing my focus points. In doing so, it was eliciting an almost trance or dream like state. This must be the hook! I could visually relax and let the selective focus offered by the crushed dof lead me.  In fully letting go, the visual images pulled me through in a way that felt entrancing, beautiful and soothing. Someone else was driving my eyes! 

In flat (i.e, deep) dof shots, like in common wide-angle shots or the majority of video work, everything on screen is largely in focus, and so we must work to pick our focal points. Framing directs us some, but we still have to sift through stimuli. Details either behind or in front of the intended subject still clamor for our attention; all equal on the flat plane of the screen. In some ways, watching flat video (like many reality shows) is draining. There are so many possible focal points on the screen competing for our attention. Not so with crushed dof footage. This control over dof is what the increasingly popular DSLRs and high-end film cameras/lenses offer. Even if we choose to focus on the blurry parts in these images, they are soft and lovely, not jarring and grabbing for our attention.

So lets consider frame rate too. When you compare the 30 frames per second rate used in most video work versus the 24 fps in most film, you have even more detail to clamor for your attention. Increasing the frame rate and the corresponding sharpness of movement it entails can be seen explicitly when using the 48 fps as in the Hobbit movie. It is jarring, unreal, in a non-soothing way. 24 fps offers the life-like blurring of movement, similar to our everyday visual perception that allows us to relax. Now, combine the crushed dof and the softer 24 frame rate, and most well shot movies make us physiologically relaxed and able to enter a more trance like open state for absorbing the story. 

What do you think? I suppose I should punt this to a neuropsychologist for commentary. Hope you are intrigued by today’s musings on sexy dof, which are arguably justification as to why I sink so much hard-earned money into Canon lenses and drag my DSLRs and multiple lenses on every shoot even though I know using my Panasonic camcorder would be oh so much easier. Oh and did I mention how much nicer the light on DSLRs is?