A quick primer on photos

By Armond Noble
This item appears on page 85 of the March 2011 issue.

In next month’s issue we’ll have the results of “Where Were You in 2010?” and I’ll announce the winners from among all the entries. Seeing where other travelers have been may give you some ideas for your next venture.

I had a letter from a reader who said he had been to every country on our nations list. Sadly, I misplaced the letter. Would you write again, please?

In the first few months of ITN’s existence, 35 years ago, we really needed photographs to print. I was at a gathering and many people were talking about their latest trips. I asked, “Did you take any photos?” And I was greeted with “Photos? I don’t want to learn all those numbers.” (And these were people with lots of letters after their names.)

It’s a knowledge of those “numbers” that makes the difference between a photograph (a mechanical reproduction) and a “picture.”

Today, most just aim their cameras and let the computer in the camera do the thinking. The camera averages everything, and the person ends up with average photographs.

A quick primer —

Let’s start with film speed. (With digital cameras, you can still set the “speed.”) There is 25, 50, 100, 200 and 400. As you noted, going up, each number is double the previous number. Going down, each number is half of the previous one. The different numbers reveal the film’s sensitivity to light. The higher numbers are called “fast” films and the low numbers indicate “slow” films. The lower-numbered films are usually finer in grain and the photographs are higher in resolution.

Next (and I will show how this all fits together to make “pictures”) is the “exposure time.” You may see on your camera 1/25, 1/50, 1/125, 1/250, 1/500, 1/1000. Those are fractions of a second and relate to how long the shutter is open, allowing light to strike the film. What you do is control light. You’ve noticed that the time progressions are also double or half, depending on which way you’re going. (Those with EE degrees can liken this to 3 dB.)

For those whose eyes may be glazing over, hang on. It will all come together soon.

Next is the lens opening. You will see 2.8, 3.5. 4, 5.6, 8, 11, 16 and 22. What those numbers represent (and NO, this will NOT be on the test) is the ratio between the diameter of the lens opening to the distance back to the film.

You don’t have to know that, but here’s what is important: each of those separate, individual numbers, when the setting is changed one level at a time, means either twice as much light is being let in or, going the other way, only half as much light is being let in than on the setting before. The 2.8 is “wide open” and the 22 is “stopped down”; that is, it’s only a very tiny hole. Those numbers are called “ƒ stops.”

Here is the important thing to remember about lenses. Some call it “depth of field” and others prefer “depth of focus.” What happens is that the focus dimension of the ƒ2.8 is very “shallow,” meaning the distance is very restricted. On the other extreme, with ƒ22, everything will be in focus from the tips of your shoes to Mt. Ararat. (Which, as we’ll see later, can be more of a handicap than a blessing.)

There’s just one other thing you have to know about lenses. They come in varieties, such as 21mm, 28mm, 35mm, 50mm, 75mm, 100mm, 200mm and, as you may have noticed at sporting events, way up from there. (Today, you don’t have to haul around a bunch of different lenses, as the “zoom” lenses incorporate all of the focal lengths.)

Now, lenses with low numbers are wide-angle. Those with higher numbers, from 200 and up, are telephoto, similar to a telescope; these are called “long” lenses. When you use longer lenses, you have to use higher shutter speeds. That’s because the longer lenses also magnify the camera shake, thus you want to shorten the exposure time to lessen that effect. As you may have noticed, when the huge telephotos are used, the camera is on a tripod to steady the camera.

Here’s where it all comes together.

The sunflower and the mountain. You are outside on a bright day. Your camera setting, with 400-speed film, is 1/250 at ƒ16. Both the close flower and the mountain are in focus. That’s the problem. In the resulting photograph, both subjects are fighting for attention!

The enlightened photographer will adjust “all those numbers” so that the sunflower is in sharp focus and the mountain is “soft.” Selective focus, it’s called, and the proper use gives pictures much more snap. As an example, in good portraits of people, the eyes are sharp and the ears are a little soft.

Also very important is the composition, that is, how the elements in the scene relate to each other.

I hope this has been of some help in turning your photographs into “pictures.”