Shutter speed is—depending on the photographic subject—the exposure control mechanism with either the most or least ’side effects’. Take a mountain, for example; one could simply mount their camera on a tripod, point it at a mountain and leave the shutter open for thirty seconds at a time (provided the film isn’t sensitive and the light isn’t high) and the difference between 30 seconds and 1/30th of a second is negligible.

It is a different story if you’re running through a crowd with the camera in your hands and trying to take pictures of a parade. 30 seconds will leave you with a picture containing only abstract smears of light—if not an outright pure white frame.

In the world of photography, rules of thumb are key. So here are a few:

The Inverse Law for Handheld Photography

Generally the lowest shutter speed one can select for a hand-held camera is the inverse of the focal length of the lens. Although we’ll get into the meaning of focal lengths in a later post, if the camera sports a lens that’s set to a focal length of 50mm (considered the ‘default’ focal length in photography by some) then you should set the shutter speed to 1/50th of a second or faster.

Guidelines For Human Motion

If a human subject is attempting to stand still for the camera, they will stay crisp up to 1/2 of a second; If a human subject is relaxed, they will stay crisp up to 1/30th of a second.

Important Note: The completely blur-free human subject in motion is not always desirable. While it’s always neat to see an athlete suspended in mid-air, face distorted and muscles strained, as clear as a bell. Moderate motion blur often adds necessary context to an action captured by a photograph.

That’s a good question, and–like most of the good questions–it engenders many different answers. Here’s mine:

Photography is a little like those woodburning sets you may have played around with as a child. You know the ones I mean? It came with wood blocks with red patterns printed on it, and a heat stylus with selectable heads with which to burn the patterns onto the wood over top of the red pattern marks? Yeah. Photography’s a lot like that.

However, instead of one electrical heat stylus, you get millions. and they’re made of light, and they’re controlled not by your hand but by the lens on your camera. But otherwise, yeah, exactly like those kits.

The light travels through the camera lens…and the spatial position of the ray origin dictates the shape of the light that strikes the film emulsion at the back of the camera. Essentially you ‘burn’ the light onto the film, etching it permanently.

The emulsion-type of the film is very important, each film strip must have a standard photosensitive reaction that remains consistant, which means that if you take two pictures under the same conditions they will be of an idential look and tone on the finished negative.

In order to have a standard measure of photosensitivity, the ISO number was developed. Let’s look at some common ones:

• ISO 100: A slower film made to shoot in daylight
• ISO 200: A very common ‘catch all’ film for snapshot cameras. Works well with daylight or flash.
• ISO 400: A faster film, often used for outdoor casual sports photography.
• ISO 800: For brighter indoor photography

There are also extremely specialized film like Agfapan 25 which is ISO 25 (makes sense). It’s used for landscapes which aren’t in the habit of moving around a lot and a photographer can afford a slower shutter speed to expose the film properly. On the other end there is ISO 1600 film used in low-light situations, it has a nasty habit of being exposed and ruined still in its canister by something no more powerful than an airport x-ray.

The nice thing about the ISO number is that it’s linear. an ISO 200 film is twice as sensitive as ISO 100 and half as sensitive as ISO 400. Put more simply: the light takes half as long to burn into the film to the same degree on ISO 400 film as it does 200.

You’d think the usefulness of being able to shoot things at high speed would mean that we’d have all just gone to the highest ISO possible. However there’s a trade off for higher speed film: it gets a LOT grainier. Interestingly enough, the higher you set the ISO sensitivity of a digital camera chip, the granier the digital image becomes too.

Thus we have the first manner to control exposure.

I imagine a great deal of you will be more concerned with megapixels than emulsions–as am I–however, every camera worth its salt relates its digital processes back into photochemical analogues, therefore for the sake of universality and comfort I will be lecturing on the assumption that we’re dealing with photochemical cameras.
Photography is the creative process of having light strike film. With any camera, there are three ways you can control the light that hits the film:

1. Aperture
2. Shutter Speed
3. Emulsion

We will be covering these seperately, in reverse order, in upcoming updates.