Sunday, 14 June 2020

Why - how it happened, and the wild connections of the wise old bird

Connections - Reaction times, Lyme Disease and the  photos.
I thought I might offer an explanation for the photos of the Barn Swallow

Was it luck? No, although I am still waiting to get the Osprey splashing in front of me. It comes with an idea. And so it was not luck but planning that enabled me to get the comet Hale-Bopp over the church in Odendorf on "Green Thursday"

or over the Effelsberg 100m radio telescope on Easter Sunday in 1997.

(These photos were on film and then digitized.)

Let me break the elements down.

1. Composition. I wanted the swallow scooping up water from the puddle. I saw it doing so several times and thought I should be able to manage a shot. But how?

2 Focal length. The bird flies very quickly so I estimated that I need a field of view comparable to the size of the puddle, about 7m long. Choose a lens or zoom focal length that includes about half the puddle. (Substitute your own noun for your shot.)

3 Focus. The event happens so quickly that the camera will not usually be able to follow the motion of such a tiny object - not necessarily always in the centre! You see the stone at the left edge of the puddle? I zoomed in on it and used the auto focus for it and then switched to manual and increased the focus to a  distance a meter or so beyond. Then I returned to the focal length covering half the puddle.

4. I didn't do the following but I would another time: set the ISO, shutter speed and aperture.

Now I must confess that the first image was a "frame grab" from a video.

However, I caught the bird in the first frame and then never again. That was on day 1. That was when I started thinking!

How fast is the bird flying? I don't know but let me pull a rabbit from the top of my head: 72kmh or 72000 meters in 3600 seconds (meters per hour). I get 20m per second, or a flyover the
puddle in circa .25 seconds.

An aside, I. At the European Southern Observatory, telescope domes were closed at wind velocities over 18m/s because dust was being picked up by the wind and was blown against  optic surfaces. I experienced such high winds in June 1972.

An aside, II. Human reaction time is approx 0.2seconds - the reason for fail starts in sprint events when the reaction of the sprinter is faster than that. Last year at Science North, Sudbury there was an experiment set up for visitors  - and staff! - to try out their times. I actually had mine measured in 2004 and that lead eventually to discovering I had Lyme Disease.
(The Lyme-related Borrelia species are collectively known as Borrelia burgdorferi sensu lato, and show a great deal of genetic diversity. )

 An electric shock was applied to my head and the time taken to reach my toes recorded. The speed ought to have been 50m/sec,  and hence the reaction time for a 2m tall person of 0.2 sec. - science!. In my case the speed was 15m per sec - so I would have been  a slow starter. (Actually in High School, Grade XII, I ran the 100m sprint in 13 sec, and the 200m in 24sec, faster over the 2nd 100m  because there was no 2nd start which would be "slow".)

Pan. Track your target through the camera lens and shoot when it is nearly at the composition centre - allow for reaction time and  camera shutter "delay" or inertia and your object will be very close to "spot on" as seen by the swallow, mouth open over the water. Panning is not obvious in this crop but in the next shot there is considerable motion blur in the background while the swallow is nearly sharp.

Here are the 2 cropped shots followed by the original, just resized:

Hope this has helped demystify the shots and not been a conceit?

Wise old bird

No comments:

Post a Comment