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How Cameras Work
Cameras capture images by focusing your subject onto a recording media through a lens.
Image Transfer
Light reflects off the subject at every point and spreads out in all directions. A lens focuses these rays back to a single point on a focal plane. The focal plane can be your eyes retina, the film in a film camera, or light sensors in a digital camera. Cameras then record the image either on a film or in some form of digital memory. Due to the way lenses work, the focused image is upside down and backwards, or rotated 180°. With your eyes, the brain turns the image around. With a film camera, just turn the film around. A digital camera turns the image for you.
Focusing
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When an image is in focus, all rays of light coming from 1 point on the subject are hitting 1 point on the focal plane. As the image goes out of focus, every point is spread out overlapping the points beside them. This is what causes blur. This spreading out can be seen in the examples to the left. |
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As the distance between the subject and the lens change, the distance between the lens and the film or sensor must change also. Most lenses now, other than disposables and some point and shoot, get very sophisticated and use many lens elements to do the job, but they still work by the same process. |
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How do fixed focus cameras work then? If they aren't adjustable, how do they focus? Simple answer, they don't. Full answer, I'll explain next week after explaining aperture. |
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Different Types of Cameras
Camera types can be classified in 2 ways, how the image is saved, and the format of the camera itself.
Image Saving Format
There are 2 main types of cameras in regards to how they save images, the film camera and the digital camera. There are specialized variations of these, but they are much less popular.
Digital cameras save images as 1's and 0's in blocks or pixels.
Film cameras record images in varying degrees of color and brightness.
We will cover details in lesson 2, "Film VS Digital Photography", as well as pointers on how to decide which type is best for you. For now, here is an image of the pupil of an eye magnified 10 times to show the difference.
digital film
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Digital camera images can be smaller or larger blocks depending on its resolution.
Film cameras can be more or less sharp depending on the film speed used.
1 mega pixel camera VS ASA 400 film |
Lesson 2 will explain more about how much detail can be captured in a picture.
Ever see those TV shows where they have a picture of a car where you can't even see the license plates, then they zoom in and they can see the letters on the plate clearly?
It's actually possible, to a degree.
Camera Format
There are several different camera formats, but the most popular ones among the average picture taker are the point and shoot and the SLR (single lens reflex). Point and shoot cameras can be fixed focus, auto focus, or manual focus. Pretty much all SLR cameras are either auto or manual focus. Some auto focus cameras even give you the option of manual focusing which is a handy feature.
Point and shoot, and SLR cameras, are available with a wide range of sophistication, from simple, to fully under your control. Most point and shoot cameras don't have interchangeable lenses, while most SLR's do.
Some other
camera types are:
Instant print - mainly Polaroid
Medium format - mostly used in professional photography
Twin Lens Reflex (TLR) - pretty much always for professional photography
See the back of this page for some pointers, and questions to ask yourself, if you're trying to decide what type of camera to get.
The Different Lenses
This section applies mostly to cameras that have interchangeable lenses, but also applies some to cameras with zoom lenses.
The 3 options, wide-angle, standard, and telephoto, cover what the average person uses, then there are more extreme versions, like the fisheye lens and super-telephoto lens, then of course is the zoom lens which is a lens that covers a range of focal lengths. Focal length is what a lens is measured by. Telephoto is a long focal length and wide-angle is a short focal length. A standard focal length is a lens/camera combination that "sees" roughly the same angle of view as the human eye. A standard focal length is considered to be equal to the diagonal of the image capturing area; in other words, the distance from one corner to the opposite corner of a negative, slide, or digital sensor. With a 35mm camera, 50mm is standard. With digital cameras, it depends on the camera, but in most cases, it's smaller.
Other lens options are capabilities, like macro focusing; or uses, like reverse mounting or extension tubes. Cameras with interchangeable lenses give far more flexibility than any camera with a permanent lens attached, but the lens isn't the only thing that determines the photos you can shoot. A professional photographer can take a better picture with a disposable camera than most people can with the most expensive camera in the world. That's what this course is all about, learning the basics so you can take better pictures.
Anyway, back to the lenses. ;-)
Standard Lens
The standard lens is what most people use most of the time. Works perfectly fine for just capturing memories, but for unique photos, you need to let the camera see what people don't normally see. You can do this either by changing your angle of view, (shoot high or low), changing how the subject is seen, (exposure or filter), or by changing the angle you see (your lens). Here's a standard lens view for comparison to the other lenses.
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A photo taken with a standard lens will generally look like what the human eye is used to seeing. Once you start changing lenses, or your focal length, the image you capture changes. If you stay in the same spot and photograph the same scene, the image captured will look the same, but how much of the scene you capture changes. A wide-angle lens will capture more of the surrounding territory, while a telephoto lens will capture less of it. Now, if you were to move in to, or away from, your subject so the subject still occupies the same amount of the scene, things start to look a little different from what we're used to seeing.
Wide-angle Lens
The wide-angle lens, as its name implies, sees a wider angle of view than normal. It captures a larger area, like if we were to back away from the subject, but it behaves a bit differently than just backing away from the subject.
If you use a wide-angle lens without changing your distance from the subject, your subject will occupy a smaller portion of the final image, as this drawing shows.
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If you were to take a head & shoulders shot of someone with a normal lens, it'll look normal, but if you use a wide-angle lens and move in closer to get the same head & shoulders shot, that person's nose would appear bigger. This is due to relative distances. If you look at something from 10' away, then move to 20' away, it'll appear to be 1/2 the size, so let's look at the head & shoulders shot.
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standard lens wide-angle lens
Can you see the difference?
As you get closer to the subject, the relative distance between the nose, eyes, and ears, is magnified, so the closer parts, like the nose, start to look bigger. If you're photographing someone with a skinny nose, this is one way to change that, but for most portrait shots, you don't want this effect.
Telephoto Lens
The telephoto lens, like a telescope, brings the subject in closer. It captures a smaller area, as if we were to move in closer, but if you're photographing a lion in the woods, how close do you want to get?
If you use a telephoto lens without changing your distance from the subject, your subject will occupy a larger portion of the final image, as this drawing shows.
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Like the wide-angle, if you were to adjust your distance to get the same shot, there will be some changes in the resulting photo. Instead of making closer things look much closer, it'll make distant things look less distant. Confusing? Your subject is 10' from you and the mountains are 2 miles away. You shoot with a standard lens. Next you use a 2x telephoto lens and shoot from twice the distance to get the same shot. The subject is twice as far away and magnified 2x so looks the same. The mountains are 2 miles and 10' away, pretty much the same distance as before, and are also magnified 2x. What happens? You only see 1/2 as much of the mountains, as if you and your subject went 1 mile closer to the mountains.
Super-telephoto Lens
A super-telephoto lens is a higher power telephoto. Anything from 2x to 4x, (100mm to 200mm for 35mm cameras), is considered a standard telephoto, while longer ones are super-telephoto. By using high magnification and changing your distance, you can get some pretty interesting shots, and with a high power lens you can get a head shot of a lion safely, or you can cheat and go to a zoo for this.
Fisheye Lens
A fisheye lens is a super-wide-angle lens. You go more than twice the normal angle of view and you see effects on the photo. You go to 3 or 4 times the angle of view, (15mm on 35mm cameras), and you start to see curvature in the image. Go to 5x, (10mm lens), and you start getting weird results.
Zoom Lens
A zoom lens is a lens that can zoom through a range of focal lengths. These are handy when you want to be able to change the angle of view quickly, but zooms don't usually have as large an aperture as its equivalent lens. We'll get into aperture next week, but it means you need more light.
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