Basic Photos 2
A doctor from the local hospital said the other day that he started medical school with a vocabulary of 10,000 words. He left knowing 16,000. So if this post on the terms of photography seems long, don't complain. At least I'm not talking about myocardial infarctions.
The important thing here is to know how these terms relate to the mechanics of a camera. I'm going to go step by step, very slowly. For most of you it will be rudimentary, but understanding the basic functions of even a fully automatic camera will improve photos like whoa.
The first terms:
Exposure — The amount of light recorded on the film (or digital equivalent).
Sharpness — Clarity of detail in the picture.
Depth of field — What is in focus; it is expressed as a range of distance measured from the closest distance in front of the camera that is in focus to the farthest.
So the depth of field in this picture is about .5 inch to 1.5 inches; that is, everything that was between half an inch and an inch and a half in front of the camera was in focus.
The depth of field in this picture is from about 2 feet to 4 feet.
The depth of field in this picture is infinity. Perhaps it's lower bound would be something like 4 or 5 feet, but the bottom of the frame starts farther out than that.
Okay, now, a camera works by capturing light. I find it more useful, however, to think of light as collecting on film. There is an exact, quantifiable amount of light that needs to accumulate on a piece of film to equal a correct exposure. Simply put, let in too little, and your picture is dark; too much, and its washed out.
Baby steps, I know.
You, the photographer, control the light in two ways. First, you control the size of the hole through which light passes. This is called the aperture. The hole can range in size from a pinhole to almost as large as the lense itself. The larger the whole, the more intense is the light hitting the film. Apertures are measured in f-stops, which are represented by seemingly arbitrary numbers, but we'll go into all of that in greater detail later in the post.
(Aside: The mechanism that makes the hole larger or smaller is called a diaphragm. Every lense actually has two pieces of glass, and the diaphragm is located in between them. Lenses are designed such that when the photographer wants the hole to be small, the diaphragm simply blocks out a greater portion of the light coming in from the outside. Without going into the optics of the lense, let's just say that the image coming through the lense is not distorted or cropped down; it is simply a dimmer version of the same image that reaches the film. A picture of the diaphragm mechanism is here, courtesy of this site.)
Second, you control how long the light is allowed to hit the film, a setting known as the shutter speed. Shutter speeds are measured in fractions of a second and literally state how long the shutter is left open.
(There are various mechanisms for shutters, none of which we need to go into now.)
Now, before we bring numbers into all of this, let's think about it conceptually. For each picture, the photographer controls the intensity and duration of the light. So you can reach your optimum exposure, a.k.a. just the right amount of light, through any number of combinations of these two factors. For instance, a big hole allows lot of light to come in quickly, so the shutter is required to be open for a much smaller amount of time. Conversely, if you reduce the hole to the size of a pinprick, you must leave the shutter open for a great deal of time to get an adequate amount of light. Medium-size hole = medium-length shutter speed.
The easiest analogy I can think of is pouring water into a bucket. The bucket represents the amount of light needed for a correct exposure. The rate at which you pour water into the bucket is equivalent to the size of your hole [/Beavis laugh], and the amount of time you spend pouring the water is your shutter speed. Whether you're using a garden hose or an eye-dropper, the end amount of water is the same.
With a photo, the other factor is that the amount of ambient light during the day, or under different weather conditions, varies wildly. Your eyeball is like the most versatile lense you can imagine. Your pupils, by the way, work the same way as a diaphragm. So in many cases, the strength of the light outside determines which combinations of shutter speed and f-stop are available for you to choose from.
Now, again, without going into the Why? of it all, the settings you choose to obtain your exposure directly affect the sharpness and the depth of field of your picture. Shutter speeds are intuitive: leave a shutter open for a long time, you get a blurry image. Snap a picture lightning fast, and it comes out extremely clear. (We'll go into flash photography in a later post.)
It's aperture that's a bit stranger. Again, because of the lense optics, the larger the hole, the shallower the depth of field. A tiny aperture leads to a much longer depth of field. A longer depth of field is often a plus because it leads to crisper focus, finer detail, etc.
Consider the following two pictures:
In the first picture, the lighting that day was poor, so I opened up my aperature as wide as it would go to allow as much light in as possible in order to keep my shutter speed quick enough to get a crisp picture. As a result, I have a shallow depth of field and the boy in the background is out of focus. In the second picture, the light that day was rather bright, so I was able to use a smaller aperture and probably about the same shutter speed as in the first picture. The result: everything from McGruff's front shoulder to the cops' winnebago in the background is in focus. This is how it works most of the time — the circumstances dictate what combination of aperture and shutter speed is called for, but there are ways to make the the differences in settings more pronounced, which is yet another lesson for another time.
All this is further complicated by a number of factors. To name just one, given a constant aperture, the depth of field will increase the farther away from the camera you focus your shot. This is why my macro shot of a pollen bud has a depth of field that measures about an inch; the pumpkins about two feet; and my beach scene infinite.
Okay, I'm going to hold off on explaining the number system behind f-stops and shutter speeds. First, I want to make sure everyone understands the interaction of these basic features. If you have any questions, leave them in comments. My many friends who already understand this stuff backward and forward, if you see some place I got muddled, let me know.
It would be largely self-defeating to go on from here without establishing this common vocabulary.
---
Holy shit, I just updated the timestamp; it took my five days to write this post. Lord 'a' mercy.
The important thing here is to know how these terms relate to the mechanics of a camera. I'm going to go step by step, very slowly. For most of you it will be rudimentary, but understanding the basic functions of even a fully automatic camera will improve photos like whoa.
The first terms:
Exposure — The amount of light recorded on the film (or digital equivalent).
Sharpness — Clarity of detail in the picture.
Depth of field — What is in focus; it is expressed as a range of distance measured from the closest distance in front of the camera that is in focus to the farthest.
So the depth of field in this picture is about .5 inch to 1.5 inches; that is, everything that was between half an inch and an inch and a half in front of the camera was in focus.
The depth of field in this picture is from about 2 feet to 4 feet.
The depth of field in this picture is infinity. Perhaps it's lower bound would be something like 4 or 5 feet, but the bottom of the frame starts farther out than that.
Okay, now, a camera works by capturing light. I find it more useful, however, to think of light as collecting on film. There is an exact, quantifiable amount of light that needs to accumulate on a piece of film to equal a correct exposure. Simply put, let in too little, and your picture is dark; too much, and its washed out.
Baby steps, I know.
You, the photographer, control the light in two ways. First, you control the size of the hole through which light passes. This is called the aperture. The hole can range in size from a pinhole to almost as large as the lense itself. The larger the whole, the more intense is the light hitting the film. Apertures are measured in f-stops, which are represented by seemingly arbitrary numbers, but we'll go into all of that in greater detail later in the post.
(Aside: The mechanism that makes the hole larger or smaller is called a diaphragm. Every lense actually has two pieces of glass, and the diaphragm is located in between them. Lenses are designed such that when the photographer wants the hole to be small, the diaphragm simply blocks out a greater portion of the light coming in from the outside. Without going into the optics of the lense, let's just say that the image coming through the lense is not distorted or cropped down; it is simply a dimmer version of the same image that reaches the film. A picture of the diaphragm mechanism is here, courtesy of this site.)
Second, you control how long the light is allowed to hit the film, a setting known as the shutter speed. Shutter speeds are measured in fractions of a second and literally state how long the shutter is left open.
(There are various mechanisms for shutters, none of which we need to go into now.)
Now, before we bring numbers into all of this, let's think about it conceptually. For each picture, the photographer controls the intensity and duration of the light. So you can reach your optimum exposure, a.k.a. just the right amount of light, through any number of combinations of these two factors. For instance, a big hole allows lot of light to come in quickly, so the shutter is required to be open for a much smaller amount of time. Conversely, if you reduce the hole to the size of a pinprick, you must leave the shutter open for a great deal of time to get an adequate amount of light. Medium-size hole = medium-length shutter speed.
The easiest analogy I can think of is pouring water into a bucket. The bucket represents the amount of light needed for a correct exposure. The rate at which you pour water into the bucket is equivalent to the size of your hole [/Beavis laugh], and the amount of time you spend pouring the water is your shutter speed. Whether you're using a garden hose or an eye-dropper, the end amount of water is the same.
With a photo, the other factor is that the amount of ambient light during the day, or under different weather conditions, varies wildly. Your eyeball is like the most versatile lense you can imagine. Your pupils, by the way, work the same way as a diaphragm. So in many cases, the strength of the light outside determines which combinations of shutter speed and f-stop are available for you to choose from.
Now, again, without going into the Why? of it all, the settings you choose to obtain your exposure directly affect the sharpness and the depth of field of your picture. Shutter speeds are intuitive: leave a shutter open for a long time, you get a blurry image. Snap a picture lightning fast, and it comes out extremely clear. (We'll go into flash photography in a later post.)
It's aperture that's a bit stranger. Again, because of the lense optics, the larger the hole, the shallower the depth of field. A tiny aperture leads to a much longer depth of field. A longer depth of field is often a plus because it leads to crisper focus, finer detail, etc.
Consider the following two pictures:
In the first picture, the lighting that day was poor, so I opened up my aperature as wide as it would go to allow as much light in as possible in order to keep my shutter speed quick enough to get a crisp picture. As a result, I have a shallow depth of field and the boy in the background is out of focus. In the second picture, the light that day was rather bright, so I was able to use a smaller aperture and probably about the same shutter speed as in the first picture. The result: everything from McGruff's front shoulder to the cops' winnebago in the background is in focus. This is how it works most of the time — the circumstances dictate what combination of aperture and shutter speed is called for, but there are ways to make the the differences in settings more pronounced, which is yet another lesson for another time.
All this is further complicated by a number of factors. To name just one, given a constant aperture, the depth of field will increase the farther away from the camera you focus your shot. This is why my macro shot of a pollen bud has a depth of field that measures about an inch; the pumpkins about two feet; and my beach scene infinite.
Okay, I'm going to hold off on explaining the number system behind f-stops and shutter speeds. First, I want to make sure everyone understands the interaction of these basic features. If you have any questions, leave them in comments. My many friends who already understand this stuff backward and forward, if you see some place I got muddled, let me know.
It would be largely self-defeating to go on from here without establishing this common vocabulary.
---
Holy shit, I just updated the timestamp; it took my five days to write this post. Lord 'a' mercy.
posted by Matt at 2:07 AM
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