The Exposure Triangle

Jul 12

A Condescending Post About Light

Something popped into my head last night. An idea for a photography video, but as this kind of video has been made a million times before I figured, fuck it! Make it for idiots.

The idea is to be as condescending as possible. Everyone I’m talking to has no idea what I’m talking about.

The Exposure Triangle.

As the name suggests, there are three parts to this: the Aperture, the Shutter Speed and the Sensor or Film Stock. All of these play a part in how much light is captured.

Photos are basically captured light.

Aperture;

This is the first gate or obstacle that light has to deal with. Like the iris in your eyes, it can open and close. But unlike your eyes, we can control how open (wide) or closed down (narrow) it is. This obviously, determines how much light moves on to the next stage (SS). The Aperture on your lens is measured in ‘f’ stops. (i.e f1.4 or f2.8) Each f stop is one ‘stop’ of light.

To increase the stop of light doubles the amount with each stop. To ‘stop down’ is to decrease light by half (50%). This is true of both Aperture and Shutter Speed.

Back to aperture. Now, opening your aperture wide or stopping it down will have another effect on your photo. The lower the f stop (the wider the aperture) the shallower your depth of field. And conversely, the higher your f stop, the more closed down (narrow) the wider your depth of field.

Depth of Field is the amount of space or distance that will be in focus. For example, with an f-stop of 1.4 for a portrait, you will have the eyes in focus, but the tip of the nose will be soft or out of focus. Your depth of field is narrow.

If however, you take the portrait with an f-stop of 2.8 or 4. You’ll find that the subject (the person whose portrait you’re taking) will be completely in focus. If that’s what you want.

If you would like to take a photo and want MORE in focus, say for a landscape or street photo, a higher f-stop would be best utilised. With f-16 most, if not all, of the photo will be in focus. Best used for landscape photography. Anything between f-4 and f-8 is good for Street Photography.

Experiment; Try locking off your camera (Setting on a tripod) and take the same photo with each f-stop setting your lens has. This will help you determine the sharpest focal point of that lens. Usually, it sits somewhere in the middle around f-8. This is the point that will give you the sharpest photos (best focus). This is why I usually use f-8 for long-exposure night photography.

Speaking of which;

2. Shutter Speed;

The second obstacle light has to contend with. Where the word aperture might be confusing, shutter speed is exactly with it sounds like, The speed of the shutter. But what is the shutter?

For the moment we’ll just assume you have a shutter that acts like a curtain (The other types are leaf and digital). So, there are two curtains, and they move together vertically in front of your camera sensor or film. Adjusting your shutter speed does two things here, first, and most obvious, it determines the speed with which it moves. But it also moves them closer together if your shutter speed is very high.

My Canon F1 35mm film camera has speeds as slow as 8 seconds and as high as 1/2000 of a second.

Let’s just unpack that for a minute. 8 seconds means that the shutter exposes the film for 8 seconds. In photography, this is a long time. When you press the shutter button, you’ll hear the shutter open, then pause: 1, 2, 3, 4, 5, 6, 7, 8 then close. During this time the film is being ‘exposed’ to light. Any movement of the camera or subject will result in motion blur. Shake a hand with extended fingers in front of your face fast to see what I mean, your fingers seem transparent. That’s motion blur.

1/2000 on the other hand is the complete opposite. It only exposes the film for 1/2000th fraction of a second. If you divide one second into 2000 equal parts, the film was exposed to light for just one of those parts. This has the effect of stopping time. You’d usually only use this speed for fast-moving objects that you want to freeze.

Slower speeds mean more light hitting the film or digital sensor so a brighter image but you get motion blur. Faster speeds mean less light hitting the film or sensor so a darker image, but you get to freeze time.

Also, each setting of Shutter Speed is either: double the amount of light with each SLOWER speed. Or half the amount of light for each faster speed. This is why, unlike with aperture, the numbers make sense. They’re either double or half.

Utilising both Aperture and Shutter Speed together to get good exposure. Meaning an image with balanced light. Or to give you a more artistic or stylised image. You might like your images to be slightly over (brighter) or under (darker) exposed. Or you might want to freeze motion or have a particular amount of motion blur. Digital cameras give you the option to play with settings to get what you want, whereas Film photography doesn’t. I’ll talk more about the pros and cons of film vs. digital, in a later post. But we have one last thing to talk about.

3. ISO;

A quick google search will tell you that ISO means: International Organization for Standardization. Though the S and the O are backwards…

ISO is the standard numerical model for light sensitivity. And again like Aperture and Shutter Speed, each setting is either half or double. But unlike Aperture and Shutter Speed, the ISO doesn’t let in more or less light. The light is already in the camera hitting the film or sensor. This setting then, adjusts the level of light sensitivity; like night vision goggles. It just boosts the available light given to it by the Aperture and the Shutter. This, again, has both good and bad points. And again, both can be used for artistic and stylistic purposes.

A low ISO, of say 100, will give you a very clear clean image, whereas a high ISO like 6400 will give you grain (for film stock) or noise (for digital sensors). With film, this is due to the fact that the light-sensitive particles of nitrate (until about 1951), acetate, and polyester are bigger so to capture an image in low light situations.

With a digital sensor, you’d get noise. This is due to boosting the electrical charge of the sensor which creates more static. We refer to this in the image as noise.

Personally, I love grain/noise and try to use a higher ISO of 3200 and 6400. With film, this will be the big number on the box, with digital, it’ll either be a dial on the top of the camera or in the settings. To shoot with a high ISO in bright light like daytime in the summer, you can use a Variable ND filter (VND).

An ND filter, or Neutral Density Filter, is a dark piece of glass you attach to the front of the lens. a VND gives you the ability to adjust the darkness of the filter. Gives you more control over how much light enters the lens before hitting that first gate, the Aperture.

Once you master the Exposer Triangle, you can get on with developing your style. If you want to copy other photographers and how they shoot, that’s fine, it’ll give you a grounding for how they capture images and it’s a good way to learn. But don’t get stuck in thinking that’ll make you a good photographer, it has the same effect as buying a £6000 Lecia M6. The camera you use is just a tool. Sure they have their own characteristics and we all have favourites. But it’s just a tool. As for copying someone else’s technique, you might get good images, you might not. Copying Ansel Adams doesn’t mean YOU’RE taking good images.

Copying is a good way to learn the craft but you need to find your own style. You can only do that by going out and taking making photos.