A grizzly sprinting at 35 miles an hour from hundred feet away will sink its teeth into your expedition cargo pants in less than two seconds, giving you just enough time to engage the autofocus, select burst mode, and press the shutter. Depending on your reaction time and camera model, your closest ones may inherit ten or twenty premortal frames that could be made into a very short viral video clip.
Reaction times for trained athletes vary from superfast 40 ms for Muhammad Ali’s fastest punches to 150 ms required to return a table tennis ball. Sprinters need 100-150 ms after registering the starting pistol to jump off the blocks.
There is a difference between the reaction time and the reflex. Reaction time is a measure how quickly an organism responds to a stimulus. In contrast, a reflex is involuntary, used to protect the body, and usually faster than a reaction. For example, the knee-jerk reflex, also called patellar reflex, is a sudden kicking movement of the lower leg in response to a sharp tap on the patellar tendon, which lies just below the kneecap, whereas the reaction time would be the time delay from noticing an obstacle on the road before the driver swerves or presses the brake, or in photography the time between noticing an object in the viewfinder and pressing the shutter.
The reflex action never needs the brain, whereas the reaction does, and it can be affected by factors, such as fatigue, drunkenness, and age. The average reaction time for humans is 0.25 seconds to a visual stimulus, 0.17 for an audio stimulus, and 0.15 seconds for a touch stimulus. As you might expect, the reaction time is not affected by sex or level of education.
As an action photographer, you might find it interesting that once an image hits the retina, it takes approximately 100 milliseconds before it consciously registers in the brain. Although the light travels much faster than sound, the human’s body visual system is actually slower than our audio system. When the light or an image hits our retina, the photons must be translated into a chemical signal that in turn must be converted into an electrical impulse that can be carried via the nerve fibres to visual cortex residing in the back portion of the brain. Visual cortex will process the input signal and split it into two entities – one processing the shape and identity of the object(s) we see, and the other decoding the location and motion of the object(s). These two streams are then combined into a final information block which is converted into conscious awareness. It’s a lot of complex data manipulation and linear processing.
Neuroscientists have discovered another problem with the real-time watching. A simple assumption is that our visual system continuously monitors the surroundings and records it in “video camera” style. In reality, we are continuously scanning the entire scene and taking a quick sample from each location. The seamless connection and stitching of the entire scene is handled by the brain that combines the individual segments into an equivalent wide-screen scene that appears like a movie or a panorama.
Speaking about panoramas, that’s why we usually can’t take a panorama in one quick look, but need to scan it thoroughly and methodically from one end to the other.
Typically, we perform about five such visual relocations per second with the minimum time of 200 milliseconds required to shift our viewpoint. Then you add 300-400 milliseconds required to execute a cognitive decision and another 50 milliseconds to engage a motor command to be communicated by nerves to the finger on the shutter. All these activities add up to 500-600 milliseconds or half a second, which may translate to several missed frames.
Case in point:
A few years ago, I was photographing a whitewater kayak race. I used a long zoom lens shooting at F8 in the single frame mode and using single-point autofocus. From my vantage point, I was able to follow the racers, focus on them, and fire off one or multiple shots in each gate. Except one tricky spot on the river with a fast and deep drop followed by a haystack. I took a number of shots before and after that spot, some better than others. When I examined images on my computer screen, I came across the following shot:
I like this image, and it was a sheer luck capturing it. Surely, I wasn’t composing and focusing for the hand with paddle. Most likely, I noticed the racer just coming down the chute, focused on him and pressed the shutter. Let’s assume that in that particular spot the water moves at 15mph (24km/h), kayak moves relatively to the water at 5 mph (8km/h), so the resulting speed is 20mph (33km/h). If the distance from the top to the bottom of that spot is 5 ft (1.5m), moving at the calculated speed, the kayak can cover 9m in a second, or 5 ft (1.5m) in 165 ms. This corresponds roughly with 100 ms required for a transmission of the image from the retina to the visual cortex, plus another 50 ms to press the shutter. And that explains the confluence of kayak being in the hole just with the hand and paddle visible behind the standing wave and click of the shutter in that very fortunate moment.
As the kayaker cleared the haystack, he was slowed down sufficiently, that I could easily focus on him in that position and make another exposure. If his speed in that moment was around 3-4 mph, he would cover in 165ms only 1 ft (30cm) which didn’t pose any problem for locking the focus or sufficient depth of field at that distance.
Back to the grizzlies:
On August 24th, 2012, in Denali National Park, a grizzly attacked and killed a lone backpacker who was photographing the bear from just over 40 yards away. He took 26 pictures of the bear with his camera over a span of seven minutes, but the bear seemed to take notice of him only for the last few seconds, according to National Park Service officials who based their assessment on satellite imagery and photo time stamps. The hiker took the first bear shots with a wide angle and then he zoomed in. The last five pictures, taken in a span of 13 seconds, show the bear lifting its head up, looking away from the camera, and then turning towards the photographer (did the hiker sneeze or yell at him?). The mauling probably occurred almost immediately after the last image.
“A bear could cover that distance before a person could react,” said the park ranger. The park service said that, based on “initial evidence,” authorities believe a bear attacked the backpacker by the river and dragged his body to a “food cache site” in a bushy area 100 to 150 yards from where the attack occurred. The bear was estimated at 600 lbs (270 kg), big for Denali. It was a mature boar, at least 5 years old.
Picture above taken by yours truly a few years ago in Denali from a safe distance, not far away from the fatal site.