Photography and movement

Hold it…

 

Photography and movement•Hold it… [Moonbeams Shop:Photography and movement]

Why are photographers always portrayed as shouting “Hold it…” before the flash gun goes off? Like all clichés, there’s something behind it.

Go to: Understanding shutter speeds and exposureWhy movement is a problemWhat can you doSo why did photographers used to shout “Hold it…”?

Understanding shutter speeds and exposure

As explained in our page Photography and light, cameras need light to work. The light from the subject goes through the lens and into the camera, and a device inside - these days an electronic one, though in the old days it was a piece of chemical film - captures the picture. Of course, if the camera did that all the time it would be continuously capturing light, so it has a device called a shutter which blocks off the light except when you actually take the photo. When you press the button to take the photo, the shutter opens for a set amount of time, the photo is taken, and the shutter closes again. Simple. The time the shutter is open for is called the ‘exposure’ time, or ‘shutter speed’. It’s usually measured in fractions of a second. A typical exposure might be 1/100th of a second.

Why movement is a problem

And as we also explained in our page Photography and light, one way to deal with situations where there is low light is to arrange for the shutter to stay open for longer. If the shutter stays open twice as long, roughly twice as much light gets into the camera. Which is fine if both the subject and the camera are perfectly still.

The trouble comes when either the subject or the camera is moving - or both. The shutter opens and a small amount of light enters the camera. Then the subject moves a bit, but the shutter is still open, so more light enters the camera but is now captured in a slightly different place. Instead of capturing a sharp image, you get a blur. The example below illustrates this:

Example of a photo blurred due to low shutter speed, in this case 1/3rd of a second [Moonbeams Shop:Photography and movement]

There’s very little we can do about blurred photographs.

What can you do

So why did photographers used to shout “Hold it…”?

As mentioned above, cameras used to use chemical film to take photographs. It wasn’t that long ago - digital photography only really became available to ordinary users at about the beginning of this century.

When photography first started - in the 1800s - the chemical films used were not very sophisticated. They took a long time to capture the image, and so exposures had to be long. Shutter speeds in those days were measured in seconds, not fractions, and being photographed required you to hold absolutely still for, maybe, twenty seconds. So much so that photographers devised mechanical devices like clamps to hold the subject’s head still. Perhaps now you can see why the people in those early photos are rarely smiling! But it was an improvement over sitting still for about a week while an artist painted your portrait, so it caught on.

Then they invented flash and things improved a bit, but even then the subject had to remain fairly still while the photographer focussed the picture (manually), held up the tray of flash powder, manually opened the shutter, ignited the flash powder and then manually closed the shutter. Still quite a performance by modern standards.

 


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