MarkBarbieri
Semi-retired
- Joined
- Aug 20, 2006
- Messages
- 6,172
Here's an attempt to explain some of the common jargon used on this board. If you have additions or corrections you'd like to see, add them to the list.
10x - The amount of zooming a lens can do is often shown as a number followed by an "x". This tells you the relative difference between the shortest and longest focal lengths of a lens. The larger the number, the bigger the difference between the widest and closest zoom settings.
You cannot tell from the number just how close a camera can zoom in. If two cameras have 10x zooms, one might go from extremely wide to somewhat zoomed in and the other may go from not very wide to extremely zoomed in. The number only tells you the range from the widest to closest, not how wide or how close it is at either extreme.
Aperture - The aperture is hole in the lens that lights come through. On most lenses, it can be adjusted in size. Larger holes let in more light. The aperture is specified as an f-number ranging from f/1.0 to f/22 or higher. Because the f-number is the focal length of the lens divided by the size of the hole, a bigger f-number represents a smaller aperture.
CCD / CMOS - CCD and CMOS are two different technologies used by image sensors (the digital camera equivalent to film). The CMOS chip has built in image processors for each pixel. The CCD relies on a separate image processor. There are several advantages and disadvantages to each approach, but from a practical standpoint, they both work about the same.
Circular Polarizer (CP) - A circular polarizer is one of two popular types of polarizers (linear being the other). It's not called circular because it is round or because it rotates. Instead, it works just like a linear polarizer, except that after it polarizes the light, it does some tricks to help your camera's exposure meter. Most Auto-exposure cameras will get confused if you use a linear polarizer, so make sure that you get a circular polarizer.
Depth-of-Field (DOF) - The range from the nearest to farthest place in your photo that is in sharp focus. If you have large depth-of-field, things very close and very far away are all in focus. If you have shallow DOF, only things the same distance from the camera are in focus. If you take a picture of a person and want the background blurry so that the person stands out, you want shallow DOF.
DOF depends on many things. The wider the aperture (lower f-number), the shallower the DOF. The longer the focal length (more zoomed in), the shallower the DOF. The farther away your subject is, the wider your depth-of-field will be.
DSLR - A digital version of an SLR.
Exposure - The exposure is the amount of light your sensor saw while you were taking the picture. Three main things affect the exposure - aperture, shutter speed, and ISO. If you adjust one of these, one or both of the others must be adjusted or your exposure will change.
Focal Length - The focal length of the lens determines the angle of view of the lens. A lens with a long (high number) focal length, like 200mm, will show a very small angle of view. A lens with a wide (low number) focal length, like 17mm, will show a very wide angle of view. A zoom lens has a range of focal lengths, like 18mm-200mm. When you zoom in on something, you are increasing the focal length. When you zoom out, you are decreasing the focal length. How "zoomed in" a particular focal length number is depends on the size of your camera's sensor. The smaller the sensor, the more "zoomed in" a given focal length number will appear. See "magnification factor" for more information.
ISO - ISO is a measure of how sensitive your sensor is. The higher the ISO, the less light the sensor requires to capture an image. That means you can use faster shutter speeds, smaller apertures, or both. ISOs range from 50 to 6400 on digital cameras. Increasing ISO brings other problems though, most notoriously increased "noise."
Magnification Factor - For a very long time, 35mm film dominated the photography world. Digital cameras replaced 35mm film with eletronic sensors. These sensors are almost always smaller than 35mm film. Because the sensor is smaller, the image needs to be magnified more to view it. That magnification affects other things, parcitularly the apparent focal length of a lens. If you take a picture with a 50mm lens on a film camera and then take a picture with the same lens on a DLSR with a 1.5x mangification factor, the second picture will appear that you zoomed in 1.5 times closer. The area that you see will actually match that of a 75mm (50mm x 1.5) lens on a film camera.
For DSLRs, magnification factors range from 1x (Canon 1Ds and 5D), 1.3x (Canon 1D), 1.5x (Pentax, Nikon, Minolta), 1.6x (Canon 30D, Rebel), and 2.0x (Olympus). Some people also call it a "crop factor" because the difference is that the image from the lens is cropped.
Noise - Noise is little dots that appear in an image. They can be the wrong color (chrominance noise) or the wrong brightness (luminance noise). They are most easily seen in areas that are supposed to be smooth colors (like blue skies). Noise is the result of very sensitive image sensors mistaking random eletronic signals as bits of light. It's the picture equivalent of static on your radio. Other things being equal, the more sensitive (higher ISO) your image sensor is, the more noise it will pick up. There are many computer tricks for reducing noise, but they all make some tradeoff between details and noise.
Polarizer - A polarizer is a filter you put on your lens to block certain types of light. Every little piece of light bounces around like a wave. Some bounce up and down; some bounce left and right; some bounce diagonally. The polarizer only lets in light bouncing in one direction.
The practical effect of this is that it can remove reflections from flat surfaces like water or glass. It can also deepen the color of the sky, especially when the sun is directly overhead or to your right or left; it doesn't work well when the sun is behind or in front of you.
To use a polarizer, look through your camera or viewfinder and rotate it. Watch the sky or reflections and see how it effects them. Rotate it until you get the effect that you want.
Be aware that because a polarizer blocks light, it makes your picture darker. Your camera will compensate with a slower shutter speed, wider aperture, or higher ISO.
Point and Shoot (P&S) - The term point and shoot refers to almost any consumer camera that isn't an SLR. They are virtually always autofocus and autoexposure. They typically use a small LCD screen to let you compose your picture. Their advantages over an SLR include being smaller, easier to operate, and sometimes having a movie mode. Their disadvantages include not being able to change lenses and having smaller sensors (which increases noise and limits control over depth-of-field).
SLR - SLR stands for Single-Lens-Reflex. As it is generally used, the term SLR refers to cameras where you look through a viewfinder that looks through camera's lens. The overwhelming majority of SLRs also allow you to switch lenses.
Shutter Speed - The length of time the shutter is open and light is hitting the camera's sensor or film. It is usually measured in fractions of a second - 1/2s is one half second.
Stop - In photography terms, a stop is a measure of light. Changes in shutter speed, aperture, and ISO are measured in stops. Changing the shutter speed by one stop changes the amount of light the camera sees by the same amount as changing the aperture or ISO by one stop.
For aperture, the "full" stop values are f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, and f/22. For ISO, the "full" stops are 100, 200, 400, 800, 1600, 3200, and 6400. For shutter speeds, the "full" stops are 1s, 1/2s, 1/4s, 1/8s, 1/15s, 1/30s, 1/60s, 1/125s, 1/250s, 1/500s, 1/1000s, 1/2000s, 1/4000s, 1/8000s.
If f/8, 1/60s, and ISO 400 gives me a proper exposure for a scene, I could decide to increase my shutter speed by two stops to 1/250s, but I would have to adjust my aperture and/or ISO to keep the exposure the same. If I decided to adjust both, I would open my aperture one stop wider by changing it to f/5.6 (remember, lower numbers mean wider apertures) and lower my ISO by one stop by changing it to ISO 200. So f/5.6, 1/250s, and ISO 800 would give me the same exposure level as f/8, 1/60s, and ISO 400.
Zoom - Zooming in or out changes the angle of view. When you zoom in, you see a smaller area, but it is magnified more. When you zoom out, it you see a greater area, but it is magnified less.
10x - The amount of zooming a lens can do is often shown as a number followed by an "x". This tells you the relative difference between the shortest and longest focal lengths of a lens. The larger the number, the bigger the difference between the widest and closest zoom settings.
You cannot tell from the number just how close a camera can zoom in. If two cameras have 10x zooms, one might go from extremely wide to somewhat zoomed in and the other may go from not very wide to extremely zoomed in. The number only tells you the range from the widest to closest, not how wide or how close it is at either extreme.
Aperture - The aperture is hole in the lens that lights come through. On most lenses, it can be adjusted in size. Larger holes let in more light. The aperture is specified as an f-number ranging from f/1.0 to f/22 or higher. Because the f-number is the focal length of the lens divided by the size of the hole, a bigger f-number represents a smaller aperture.
CCD / CMOS - CCD and CMOS are two different technologies used by image sensors (the digital camera equivalent to film). The CMOS chip has built in image processors for each pixel. The CCD relies on a separate image processor. There are several advantages and disadvantages to each approach, but from a practical standpoint, they both work about the same.
Circular Polarizer (CP) - A circular polarizer is one of two popular types of polarizers (linear being the other). It's not called circular because it is round or because it rotates. Instead, it works just like a linear polarizer, except that after it polarizes the light, it does some tricks to help your camera's exposure meter. Most Auto-exposure cameras will get confused if you use a linear polarizer, so make sure that you get a circular polarizer.
Depth-of-Field (DOF) - The range from the nearest to farthest place in your photo that is in sharp focus. If you have large depth-of-field, things very close and very far away are all in focus. If you have shallow DOF, only things the same distance from the camera are in focus. If you take a picture of a person and want the background blurry so that the person stands out, you want shallow DOF.
DOF depends on many things. The wider the aperture (lower f-number), the shallower the DOF. The longer the focal length (more zoomed in), the shallower the DOF. The farther away your subject is, the wider your depth-of-field will be.
DSLR - A digital version of an SLR.
Exposure - The exposure is the amount of light your sensor saw while you were taking the picture. Three main things affect the exposure - aperture, shutter speed, and ISO. If you adjust one of these, one or both of the others must be adjusted or your exposure will change.
Focal Length - The focal length of the lens determines the angle of view of the lens. A lens with a long (high number) focal length, like 200mm, will show a very small angle of view. A lens with a wide (low number) focal length, like 17mm, will show a very wide angle of view. A zoom lens has a range of focal lengths, like 18mm-200mm. When you zoom in on something, you are increasing the focal length. When you zoom out, you are decreasing the focal length. How "zoomed in" a particular focal length number is depends on the size of your camera's sensor. The smaller the sensor, the more "zoomed in" a given focal length number will appear. See "magnification factor" for more information.
ISO - ISO is a measure of how sensitive your sensor is. The higher the ISO, the less light the sensor requires to capture an image. That means you can use faster shutter speeds, smaller apertures, or both. ISOs range from 50 to 6400 on digital cameras. Increasing ISO brings other problems though, most notoriously increased "noise."
Magnification Factor - For a very long time, 35mm film dominated the photography world. Digital cameras replaced 35mm film with eletronic sensors. These sensors are almost always smaller than 35mm film. Because the sensor is smaller, the image needs to be magnified more to view it. That magnification affects other things, parcitularly the apparent focal length of a lens. If you take a picture with a 50mm lens on a film camera and then take a picture with the same lens on a DLSR with a 1.5x mangification factor, the second picture will appear that you zoomed in 1.5 times closer. The area that you see will actually match that of a 75mm (50mm x 1.5) lens on a film camera.
For DSLRs, magnification factors range from 1x (Canon 1Ds and 5D), 1.3x (Canon 1D), 1.5x (Pentax, Nikon, Minolta), 1.6x (Canon 30D, Rebel), and 2.0x (Olympus). Some people also call it a "crop factor" because the difference is that the image from the lens is cropped.
Noise - Noise is little dots that appear in an image. They can be the wrong color (chrominance noise) or the wrong brightness (luminance noise). They are most easily seen in areas that are supposed to be smooth colors (like blue skies). Noise is the result of very sensitive image sensors mistaking random eletronic signals as bits of light. It's the picture equivalent of static on your radio. Other things being equal, the more sensitive (higher ISO) your image sensor is, the more noise it will pick up. There are many computer tricks for reducing noise, but they all make some tradeoff between details and noise.
Polarizer - A polarizer is a filter you put on your lens to block certain types of light. Every little piece of light bounces around like a wave. Some bounce up and down; some bounce left and right; some bounce diagonally. The polarizer only lets in light bouncing in one direction.
The practical effect of this is that it can remove reflections from flat surfaces like water or glass. It can also deepen the color of the sky, especially when the sun is directly overhead or to your right or left; it doesn't work well when the sun is behind or in front of you.
To use a polarizer, look through your camera or viewfinder and rotate it. Watch the sky or reflections and see how it effects them. Rotate it until you get the effect that you want.
Be aware that because a polarizer blocks light, it makes your picture darker. Your camera will compensate with a slower shutter speed, wider aperture, or higher ISO.
Point and Shoot (P&S) - The term point and shoot refers to almost any consumer camera that isn't an SLR. They are virtually always autofocus and autoexposure. They typically use a small LCD screen to let you compose your picture. Their advantages over an SLR include being smaller, easier to operate, and sometimes having a movie mode. Their disadvantages include not being able to change lenses and having smaller sensors (which increases noise and limits control over depth-of-field).
SLR - SLR stands for Single-Lens-Reflex. As it is generally used, the term SLR refers to cameras where you look through a viewfinder that looks through camera's lens. The overwhelming majority of SLRs also allow you to switch lenses.
Shutter Speed - The length of time the shutter is open and light is hitting the camera's sensor or film. It is usually measured in fractions of a second - 1/2s is one half second.
Stop - In photography terms, a stop is a measure of light. Changes in shutter speed, aperture, and ISO are measured in stops. Changing the shutter speed by one stop changes the amount of light the camera sees by the same amount as changing the aperture or ISO by one stop.
For aperture, the "full" stop values are f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, and f/22. For ISO, the "full" stops are 100, 200, 400, 800, 1600, 3200, and 6400. For shutter speeds, the "full" stops are 1s, 1/2s, 1/4s, 1/8s, 1/15s, 1/30s, 1/60s, 1/125s, 1/250s, 1/500s, 1/1000s, 1/2000s, 1/4000s, 1/8000s.
If f/8, 1/60s, and ISO 400 gives me a proper exposure for a scene, I could decide to increase my shutter speed by two stops to 1/250s, but I would have to adjust my aperture and/or ISO to keep the exposure the same. If I decided to adjust both, I would open my aperture one stop wider by changing it to f/5.6 (remember, lower numbers mean wider apertures) and lower my ISO by one stop by changing it to ISO 200. So f/5.6, 1/250s, and ISO 800 would give me the same exposure level as f/8, 1/60s, and ISO 400.
Zoom - Zooming in or out changes the angle of view. When you zoom in, you see a smaller area, but it is magnified more. When you zoom out, it you see a greater area, but it is magnified less.
