Friday, July 3, 2009

Zoom! Zoom!

I used to love tossing questions out to my science classes when that was what I taught primarily - questions of the sort where the common sense answers aren't the right ones. An example: If a bird is flying 2 feet above the ground and another bird is flying 50 feet off the ground, which will cast the larger shadow? The "obvious" answer is that the bird 50 feet up will because it's closer to the light source. The correct answer, though, is that both shadows will be the same size (Without arguing millimicrons.) because the light source is 93 million miles away and the 48 feet of difference between the birds is insignificant.

I stumped myself with a similar "riddle" this morning after I took this photo on the deck and then decided that I'd do the same with the scooter - get a picture of the scooter in perfect focus with the background all fuzzy.

I pulled in a tight zoom on the little fountain, focused on it and voila! The camera did the rest all by itself as it did with the plants growing in the planters that sit on the deck rail. The background trees in both photos were about 50 feet away from the camera; the foregrounds were about 5 feet away.

I knew just the spot where I'd do the same thing with the scooter - the municipal park in Plains that I wrote about last year. It sits high atop a hill overlooking the cozy looking neighborhood below. I'd be able to tighten up the zoom on the scooter and the camera would do the same thing it did on the deck!

Here's the scene I started with...

I zoomed in on the bike, snapped, and groaned. It didn't work! The zoom flattened out the depth just as I expected it would, but the background wasn't fuzzy! I know this is somehow related to that light source being 93 million miles away, but I'd be darned before I could spell it out with the appropriate physics.

Now if I dig through the photography books collecting dust on my shelves (I buy them for the pictures.) I'll read how something about adjusting the aperture will change the depth of field, yada, yada, yada. I think I played with that in the past with the camera on manual settings, but I don't think I was ever able to get the shutter speed just right so that the resulting pictures weren't too dark or too bright.

Doing stuff like this gives me great respect for the "real" photographers who shot on film for most of their careers and couldn't see their shots until they went through all the trouble of developing and printing their photos. They had to carry all sorts of rules and charts around in their heads and if they screwed up somebody's wedding pictures, for example, there was no second chance. I'm often conscious of this when I'm watching a movie shot in dim light. How do they know there's enough illumination for them to get the scenes as they want them to be? I guess that's what the fancy title of cinematographer is for.

Yesterday I chased the train. Today the train chased me. I'd positioned the BV beneath the train trestle in front of some power grids to try to get the cycle in focus with the towers behind it blurred and then heard the telltale rumble of the train that would soon pass directly overhead. I ran back to the scooter and moved it in time to get this shot of the train rolling over the Susquehanna on the bridge that the trainmen who run it call "the gauntlet."

I've heard stories of conductors who had to walk the lengths of broken trains on winter nights over this bridge which has no handrails nor platforms alongside the tracks with the unforgiving river below. All in all, in spite of my romantic notions of running a train, if I had my druthers (or the choice druthers of somebody dear) I'd rather be curled up on a cold night with a photography book reading all sorts of things about apertures and shutter speeds that will escape me entirely when I need them.


Lance said...

Joe, nice post and great pictures. I probably just haven't noticed it before, but I like the milkcrate carrier you use on your Piaggio.

sixstring563 said...

I read somewhere where most point & shoot digital lenses have tremendous depth of field and I think if I remember correctly it said something about it being related to the fairly small size of the lens compared to larger cameras.

I'm betting your photo books suggested trying a wide aperature (small f#), fast shutter speed, and tight zoom.

Along with the scooter, I'm loving the train education. Speaking of trains over water... check out the mysterious circumstances of the death of baseball hall of famer Ed Delahanty in the early 20th century. Many believe he was tossed off a train bridge near Niagara Falls in the early 20th century after a drunken rowdy disturbance on the train. He was a distant relative.

Doug K. said...

If your camera has an "Aperture Priority" mode you can use that and then set a large aperture (smaller f-number). Most point-n-shoot cameras though will only go to about f4-5 which still gives you quite a bit of depth of field. Getting waaay back from your subject and using the zoom will force the camera to it's smaller aperture and probably give you the results you're after.

Of course further back and tighter zoom means there will be more problem with shaky hands and then a small tripod or monopod is handy. I carry a small tripod about 6" tall with velcro on one leg so it can be strapped to tree branches, hand rails, the bike, or whatever to create a stable platform.

At least with digital you can afford to experiment!