Color temperature: "Because it is the standard against which other light sources are compared, the color temperature of the thermal radiation from an ideal black body radiator is defined as equal to its surface temperature in kelvin, or alternatively in mired (micro-reciprocal degrees kelvin).[1] For source other than ideal black bodies, the color temperature of the thermal radiation emitted from it may differ from its actual surface temperature. In an incandescent light bulb the light is of thermal origin and is very close to that of an ideal black-body radiator.
However, many other light sources, such as fluorescent lamps, emit light primarily by processes other than raising the temperature of a body. This means the emitted radiation does not follow the form of a black-body spectrum. These sources are assigned what is known as a correlated color temperature (CCT). CCT is the color temperature of a black body radiator which to human color perception most closely matches the light from the lamp. Because such an approximation is not required for incandescent light, the CCT for an incandescent light is simply its unadjusted temperature, derived from the comparison to a black body radiator."
Saturday, November 15, 2008
Friday, November 7, 2008
Controlling the photographic exposure and rendering
Camera controls are inter-related. The total amount of light reaching the film plane (the "exposure") changes with the duration of exposure, aperture of the lens, and, the effective focal length of the lens (which in variable focal length lenses, can change as the lens is zoomed). Changing any of these controls can alter the exposure. Many cameras may be set to adjust most or all of these controls automatically. This automatic functionality is useful for occasional photographers in many situations.
The duration of an exposure is referred to as shutter speed, often even in cameras that don't have a physical shutter, and is typically measured in fractions of a second. Aperture is expressed by an f-number or f-stop (derived from focal ratio), which is proportional to the ratio of the focal length to the diameter of the aperture. If the f-number is decreased by a factor of 
, the aperture diameter is increased by the same factor, and its area is increased by a factor of 2. The f-stops that might be found on a typical lens include 2.8, 4, 5.6, 8, 11, 16, 22, 32, where going up "one stop" (using lower f-stop numbers) doubles the amount of light reaching the film, and stopping down one stop halves the amount of light.
Exposures can be achieved through various combinations of shutter speed and aperture. For example, f/8 at 8 ms (=1/125th of a second) and f/5.6 at 4 ms (=1/250th of a second) yield the same amount of light. The chosen combination has an impact on the final result. In addition to the subject or camera movement that might vary depending on the shutter speed, the aperture (and focal length of the lens) determine the depth of field, which refers to the range of distances from the lens that will be in focus. For example, using a long lens and a large aperture (f/2.8, for example), a subject's eyes might be in sharp focus, but not the tip of the nose. With a smaller aperture (f/22), or a shorter lens, both the subject's eyes and nose can be in focus. With very small apertures, such as pinholes, a wide range of distance can be brought into focus.
Image capture is only part of the image forming process. Regardless of material, some process must be employed to render the latent image captured by the camera into the final photographic work. This process consists of two steps, development and printing.
During the printing process, modifications can be made to the print by several controls. Many of these controls are similar to controls during image capture, while some are exclusive to the printing process. Most controls have equivalent digital concepts, but some create different effects. For example, dodging and burning controls are different between digital and film processes. Other printing modifications include:
- Chemicals and process used during film development
- Duration of exposure – equivalent to shutter speed
- Printing aperture – equivalent to aperture, but has no effect on depth of field
- Contrast
- Dodging – reduces exposure of certain print areas, resulting in lighter areas
- Burning – increases exposure of certain areas, resulting in darker areas
- Paper texture – glossy, matte, etc
- Paper type – resin-coated (RC) or fiber-based (FB)
- Paper size
- Toners – used to add warm or cold tones to black and white prints
Wikipedia
Photographic cameras
The camera or camera obscura is the image-forming device, and photographic film or a silicon electronic image sensor is the sensing medium. The respective recording medium can be the film itself, or a digital electronic or magnetic memory.
Photographers control the camera and lens to "expose" the light recording material (such as film) to the required amount of light to form a "latent image" (on film) or "raw file" (in digital cameras) which, after appropriate processing, is converted to a usable image. Digital cameras replace film with an electronic image sensor based on light-sensitive electronics such as charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) technology. The resulting digital image is stored electronically, but can be reproduced on paper or film.
The movie camera is a type of photographic camera which takes a rapid sequence of photographs on strips of film. In contrast to a still camera, which captures a single snapshot at a time, the movie camera takes a series of images, each called a "frame". This is accomplished through an intermittent mechanism. The frames are later played back in a movie projector at a specific speed, called the "frame rate" (number of frames per second). While viewing, a person's eyes and brain merge the separate pictures together to create the illusion of motion.
In all but certain specialized cameras, the process of obtaining a usable exposure must involve the use, manually or automatically, of a few controls to ensure the photograph is clear, sharp and well illuminated. The controls usually include but are not limited to the following:
Wikipedia
Photographers control the camera and lens to "expose" the light recording material (such as film) to the required amount of light to form a "latent image" (on film) or "raw file" (in digital cameras) which, after appropriate processing, is converted to a usable image. Digital cameras replace film with an electronic image sensor based on light-sensitive electronics such as charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) technology. The resulting digital image is stored electronically, but can be reproduced on paper or film.
The movie camera is a type of photographic camera which takes a rapid sequence of photographs on strips of film. In contrast to a still camera, which captures a single snapshot at a time, the movie camera takes a series of images, each called a "frame". This is accomplished through an intermittent mechanism. The frames are later played back in a movie projector at a specific speed, called the "frame rate" (number of frames per second). While viewing, a person's eyes and brain merge the separate pictures together to create the illusion of motion.
In all but certain specialized cameras, the process of obtaining a usable exposure must involve the use, manually or automatically, of a few controls to ensure the photograph is clear, sharp and well illuminated. The controls usually include but are not limited to the following:
- Focus - the adjustment to place the sharpest focus where it is desired on the subject.
- Aperture – adjustment of the iris, measured as f-number, which controls the amount of light passing through the lens. Aperture also has an effect on focus and depth of field, namely, the smaller the opening [aperture], the less light but the greater the depth of field--that is, the greater the range within which objects appear to be sharply focused. The current focal length divided by the f-number gives the actual aperture size in millimeters.
- Shutter speed – adjustment of the speed (often expressed either as fractions of seconds or as an angle, with mechanical shutters) of the shutter to control the amount of time during which the imaging medium is exposed to light for each exposure. Shutter speed may be used to control the amount of light striking the image plane; 'faster' shutter speeds (that is, those of shorter duration) decrease both the amount of light and the amount of image blurring from motion of the subject and/or camera.
- White balance – on digital cameras, electronic compensation for the color temperature associated with a given set of lighting conditions, ensuring that white light is registered as such on the imaging chip and therefore that the colors in the frame will appear natural. On mechanical, film-based cameras, this function is served by the operator's choice of film stock. In addition to using white balance to register natural coloration of the image, photographers may employ white balance to aesthetic end, for example white balancing to a blue object in order to obtain a warm color temperature.
- Metering – measurement of exposure so that highlights and shadows are exposed according to the photographer's wishes. Many modern cameras meter and set exposure automatically. Before automatic exposure, correct exposure was accomplished with the use of a separate light metering device or by the photographer's knowledge and experience of gauging correct settings. To translate the amount of light into a usable aperture and shutter speed, the meter needs to adjust for the sensitivity of the film or sensor to light. This is done by setting the "film speed" or ISO sensitivity into the meter.
- ISO speed – traditionally used to "tell the camera" the film speed of the selected film on film cameras, ISO speeds are employed on modern digital cameras as an indication of the system's gain from light to numerical output and to control the automatic exposure system. A correct combination of ISO speed, aperture, and shutter speed leads to an image that is neither too dark nor too light.
- Auto-focus point – on some cameras, the selection of a point in the imaging frame upon which the auto-focus system will attempt to focus. Many Single-lens reflex cameras (SLR) feature multiple auto-focus points in the viewfinder.
- Focal length and type of lens (telephoto or "long" lens, macro, wide angle, fisheye, or zoom)
- Filters placed between the subject and the light recording material, either in front of or behind the lens
- Inherent sensitivity of the medium to light intensity and color/wavelengths.
- The nature of the light recording material, for example its resolution as measured in pixels or grains of silver halide.
Wikipedia
Tuesday, November 4, 2008
Changing Your Camera's Mind
Testing Your Camera
Thanks to digital, you can easily test the latitude of your camera and find out exactly how it will render tones. Follow this process to find out at exactly which point your camera begins to lose detail in the highlights and shadows. With this knowledge you will know what you're camera will do to a scene before you trip the shutter.
Find any colorless, single-toned subject; a white wall works well. You're going to take a series of photographs of it at several different exposures. Switch into manual mode, meter the wall, and photograph it just at the settings your camera recommends. That's you're middle gray exposure. Now take exposures as you lower the shutter speed by each setting (1/3 or 1/2 stop) up to 3 stops overexposed. Repeat the process in the other direction from your middle gray down to 3 stops underexposed.
You've just created a gray chart that will tell you at what point your camera renders pure whites and blacks. Looking at the histograms of these images will tell you how your camera treats various exposures.
First look for which exposure shows your highlights (whites) beginning to clip on the right side of the scale. It's usually between 2-3 stops overexposed, depending on your camera. If my whites begin to clip at 3 stops over, then whenever I'm using that camera I would never want my whites to be more than 3 stops higher that my meter's middle gray reading. Knowing this tells me how to meter my highlights, and they are the most important tones to control in exposure.
Another thing to notice from the test is how your shadows react differently than your highlights. Look at your histograms in the underexposed frames. It takes the shadow frames reach a true black, as opposed to the highlights which race to the clipping point. Highlights lose detail quickly. With some cameras the highlights begin to lose detail only two stops over middle gray, while the shadows retain detail as much as 3.5 stops under.
Knowing your camera's limits will help you push things to the edge without falling off.
Exposure Compensation
There are times when it's a good idea to photograph in an auto-exposure mode. I'm thinking of situations where the lighting is changing quickly and you're trying to capture moments. In such situations you don't always have time to check your exposure. If you have to shoot in auto-exposure mode, learn to use your camera's exposure compensation setting.
Exposure compensation lets you tell your camera to under or overexpose by an amount you set. For example, if you are taking pictures on a family ski outing, the bright snow is going to throw off your meter. You can compensate for this by setting your exposure compensation to +1.5 stops, which will cause your camera to overexpose by that amount and keep the snow white. (Of course, make some test frames before you take my word for it! I don't want to be responsible for destroying the memories of your family ski trip.)
If you're photographing someone in front of a black wall, you can compensate by setting your exposure compensation to -1 or more stops, so that it underexposes. By making a few exposures and checking them on your LCD screen, you can narrow in on the exact setting for your situation.
WARNING!!! Don't forget to turn off exposure compensation when you no longer need it. As long as it's active, every photograph you take will be over or underexposed to the level you set. Most cameras have an indicator to remind you that exposure compensation is set, but I guarantee that you will forget that it's on from time to time.
www.zibtips.com
Thanks to digital, you can easily test the latitude of your camera and find out exactly how it will render tones. Follow this process to find out at exactly which point your camera begins to lose detail in the highlights and shadows. With this knowledge you will know what you're camera will do to a scene before you trip the shutter.
Find any colorless, single-toned subject; a white wall works well. You're going to take a series of photographs of it at several different exposures. Switch into manual mode, meter the wall, and photograph it just at the settings your camera recommends. That's you're middle gray exposure. Now take exposures as you lower the shutter speed by each setting (1/3 or 1/2 stop) up to 3 stops overexposed. Repeat the process in the other direction from your middle gray down to 3 stops underexposed.
You've just created a gray chart that will tell you at what point your camera renders pure whites and blacks. Looking at the histograms of these images will tell you how your camera treats various exposures.
First look for which exposure shows your highlights (whites) beginning to clip on the right side of the scale. It's usually between 2-3 stops overexposed, depending on your camera. If my whites begin to clip at 3 stops over, then whenever I'm using that camera I would never want my whites to be more than 3 stops higher that my meter's middle gray reading. Knowing this tells me how to meter my highlights, and they are the most important tones to control in exposure.
Another thing to notice from the test is how your shadows react differently than your highlights. Look at your histograms in the underexposed frames. It takes the shadow frames reach a true black, as opposed to the highlights which race to the clipping point. Highlights lose detail quickly. With some cameras the highlights begin to lose detail only two stops over middle gray, while the shadows retain detail as much as 3.5 stops under.
Knowing your camera's limits will help you push things to the edge without falling off.
Exposure Compensation
There are times when it's a good idea to photograph in an auto-exposure mode. I'm thinking of situations where the lighting is changing quickly and you're trying to capture moments. In such situations you don't always have time to check your exposure. If you have to shoot in auto-exposure mode, learn to use your camera's exposure compensation setting.
Exposure compensation lets you tell your camera to under or overexpose by an amount you set. For example, if you are taking pictures on a family ski outing, the bright snow is going to throw off your meter. You can compensate for this by setting your exposure compensation to +1.5 stops, which will cause your camera to overexpose by that amount and keep the snow white. (Of course, make some test frames before you take my word for it! I don't want to be responsible for destroying the memories of your family ski trip.)
If you're photographing someone in front of a black wall, you can compensate by setting your exposure compensation to -1 or more stops, so that it underexposes. By making a few exposures and checking them on your LCD screen, you can narrow in on the exact setting for your situation.
WARNING!!! Don't forget to turn off exposure compensation when you no longer need it. As long as it's active, every photograph you take will be over or underexposed to the level you set. Most cameras have an indicator to remind you that exposure compensation is set, but I guarantee that you will forget that it's on from time to time.
www.zibtips.com
Histogram
The Scientific Meter
Learning about the histogram is a little daunting at first. But stick with me here. The histogram is a feature well worth spending a few minutes to grasp. Being able to read the information in a histogram will make you a master of exposure.
The histogram is simply a graph that displays the tones in your photograph. The graph runs from dark to light in 255 steps. The dark areas (shadows) are graphed on the left and lighter areas (highlights) to the right. The far left of the scale is perfect black and the far right is perfect white.
If you over or underexpose your photograph, pixel data will run off the chart to the right or left. This is called clipping. And it is bad. In a good exposure, all of your graphed pixel data will stay on the chart. Information that goes off the scale to the left or right is basically lost data (pixels to the right will be recorded as pure white and those to the left as pure black). So try to keep it all on the chart.
photography and histograms On your camera's LCD screen, the histogram can be checked to ensure your exposure settings were right for the given photograph. When I start to photograph in any lighting situation I'll select my shutter speed and aperture settings and make a test exposure. Then I look at the histogram of the test on my camera's LCD screen. The histogram gives me a perfect indication of where my exposure is. If my highlights or shadows are clipping, I can make a quick adjustment to perfect the exposure. Then, until the light changes, I don't have to think about exposure. I know it's dead-on.
The Typical Histogram
The typical histogram will have a bell curve in the middle (the midtones), as most tones in photographs are average tones. On the left side of the graph, the shadows should drop off without hitting the edge of the graph, as should the highlights on the right. Anything going off the edge of the graph is tone information clipped off the scale, usually caused by an incorrect exposure setting. Again, a proper exposure generally keeps all of the graph visible in the scale, avoiding clipping.
Right and Wrong
Above is an example of the histogram of an overexposed photograph. Notice how the highlights at the right of the graph scale up and off the chart. And the shadows at left trail off too far from the edge (meaning I don't have any black in my photograph).
Below is an example of the histogram of an underexposed photograph. It's the same problem, only reversed. While this photograph doesn't have much in terms of highlights, underexposing means we've lost a lot of shadow detail.
Now look again at the histogram on the flower photograph at the top of this tip. You'll see how the tones in that correctly exposed histogram are smooth and mostly fall within the edges of the graph.
On the Computer
Most digital imaging software will display histograms, and slider controls usually appear below the histogram for adjusting the tones in the image. If you move the shadows slider, everything to the left of it will register as completely black. If you move the highlights slider, everything to the right of it will register as completely white. The midtones slider will affect the overall brightness.
In the days of the darkroom, one of the first lessons to learn was how to get a true black in your print. It wasn't intuitive, and many photographers will remember being sent back into the darkroom to try again until they successfully completed the lesson. With the histogram, you can instantly achieve that true black, as well as a true white. And the graph of the histogram gives you mathematical proof.
Protect Your Highlights
If you have to lean one way or the other in exposure, always protect your highlights. Don't let them fly off the right side of the histogram. You're better off slightly underexposing if you have to. Detail in overexposed highlights is lost and basically unrecoverable. Your shadows are much more flexible and can be lightened to recover lost detail.
www.zibtips.com
Learning about the histogram is a little daunting at first. But stick with me here. The histogram is a feature well worth spending a few minutes to grasp. Being able to read the information in a histogram will make you a master of exposure.
The histogram is simply a graph that displays the tones in your photograph. The graph runs from dark to light in 255 steps. The dark areas (shadows) are graphed on the left and lighter areas (highlights) to the right. The far left of the scale is perfect black and the far right is perfect white.
If you over or underexpose your photograph, pixel data will run off the chart to the right or left. This is called clipping. And it is bad. In a good exposure, all of your graphed pixel data will stay on the chart. Information that goes off the scale to the left or right is basically lost data (pixels to the right will be recorded as pure white and those to the left as pure black). So try to keep it all on the chart.
photography and histograms On your camera's LCD screen, the histogram can be checked to ensure your exposure settings were right for the given photograph. When I start to photograph in any lighting situation I'll select my shutter speed and aperture settings and make a test exposure. Then I look at the histogram of the test on my camera's LCD screen. The histogram gives me a perfect indication of where my exposure is. If my highlights or shadows are clipping, I can make a quick adjustment to perfect the exposure. Then, until the light changes, I don't have to think about exposure. I know it's dead-on.The Typical Histogram
The typical histogram will have a bell curve in the middle (the midtones), as most tones in photographs are average tones. On the left side of the graph, the shadows should drop off without hitting the edge of the graph, as should the highlights on the right. Anything going off the edge of the graph is tone information clipped off the scale, usually caused by an incorrect exposure setting. Again, a proper exposure generally keeps all of the graph visible in the scale, avoiding clipping.
Right and Wrong
Above is an example of the histogram of an overexposed photograph. Notice how the highlights at the right of the graph scale up and off the chart. And the shadows at left trail off too far from the edge (meaning I don't have any black in my photograph).Below is an example of the histogram of an underexposed photograph. It's the same problem, only reversed. While this photograph doesn't have much in terms of highlights, underexposing means we've lost a lot of shadow detail.
Now look again at the histogram on the flower photograph at the top of this tip. You'll see how the tones in that correctly exposed histogram are smooth and mostly fall within the edges of the graph.On the Computer
Most digital imaging software will display histograms, and slider controls usually appear below the histogram for adjusting the tones in the image. If you move the shadows slider, everything to the left of it will register as completely black. If you move the highlights slider, everything to the right of it will register as completely white. The midtones slider will affect the overall brightness.
In the days of the darkroom, one of the first lessons to learn was how to get a true black in your print. It wasn't intuitive, and many photographers will remember being sent back into the darkroom to try again until they successfully completed the lesson. With the histogram, you can instantly achieve that true black, as well as a true white. And the graph of the histogram gives you mathematical proof.
Protect Your Highlights
If you have to lean one way or the other in exposure, always protect your highlights. Don't let them fly off the right side of the histogram. You're better off slightly underexposing if you have to. Detail in overexposed highlights is lost and basically unrecoverable. Your shadows are much more flexible and can be lightened to recover lost detail.
www.zibtips.com
Getting Exposures in Photography Right
Photo Exposure - Highlights and Shadows
Your camera's meter is smart enough to get you a good exposure for most average scenes. But it isn't smart enough to know what it's looking at, and it can easily be thrown off by bright or dark subjects. And since your meter is trying to average your photograph into an 18% gray tone, it's going to underexpose bright scenes and overexpose dark scenes. To take your photography and exposures to the next level you need to know when to override the advice your meter is giving you.
I'm going to explain how to expose for highlights and shadows. Of course, if you're using a handheld incident meter, you can move along. This tip addresses reflective meters like the one in your camera.
This concept was a breakthrough for me when I was starting out in photography. It might take you some thinking to grasp this, but it's worth it. The most important thing is this:
With bright subjects, you need to add light to the meter's recommendation. With dark subjects, you need to subtract light from the meter's recommendation. That's how you achieve a correct exposure.
Exposure - Light Subjects
Your meter wants everything to be gray, even when you point a camera meter at a white subject. To make the white turn into gray, the meter will suggest underexposing. Think about when you exit a dark movie theater and find yourself in the bright outdoors. Your instinct is to squint to keep things dark until your eyes adjust to the bright light.
But you don't want a squinty, dim photo. You want your white object to appear white. Otherwise the photo will lack the proper contrast and appear flat or dull.
So instead of squinting, you need to override your meter and adjust your camera in the other direction. You actually need to let in more light than your meter suggests so that the white object will appear white. That's the secret. More light in your exposure equals brighter tones.
I'll talk about calibrating your camera later on, but most whites fall around two stops over the 18% gray that your meter suggests. So you can meter a white and open approximately two stops (again, test your camera to be sure) to achieve a good white that still has a minimum of detail.
Exposure - Dark Subjects
Dark subjects work on the same principle as light subjects, but in reverse. In order to stay dark, they need less light, less exposure. So if you're metering off a black object, you'll need to close down to a smaller aperture or else raise your shutter speed.
A good black will fall around two and a half stops under the 18% gray that your meter suggests. Again, test your camera to be sure.
Conclusion
So to re-cap, with bright subjects you need to overexpose from your meter's reading. Bright objects need more light so they can remain bright. And in the opposite direction, dark subjects need to be underexposed from your meter reading. Dark objects need less light so they can remain dark.
Once you are able to visualize that principle of light, you're on your way to understanding exposure and having great exposures in your photography
www.zibtips.com
Your camera's meter is smart enough to get you a good exposure for most average scenes. But it isn't smart enough to know what it's looking at, and it can easily be thrown off by bright or dark subjects. And since your meter is trying to average your photograph into an 18% gray tone, it's going to underexpose bright scenes and overexpose dark scenes. To take your photography and exposures to the next level you need to know when to override the advice your meter is giving you.
I'm going to explain how to expose for highlights and shadows. Of course, if you're using a handheld incident meter, you can move along. This tip addresses reflective meters like the one in your camera.
This concept was a breakthrough for me when I was starting out in photography. It might take you some thinking to grasp this, but it's worth it. The most important thing is this:
With bright subjects, you need to add light to the meter's recommendation. With dark subjects, you need to subtract light from the meter's recommendation. That's how you achieve a correct exposure.
Exposure - Light Subjects
Your meter wants everything to be gray, even when you point a camera meter at a white subject. To make the white turn into gray, the meter will suggest underexposing. Think about when you exit a dark movie theater and find yourself in the bright outdoors. Your instinct is to squint to keep things dark until your eyes adjust to the bright light.
But you don't want a squinty, dim photo. You want your white object to appear white. Otherwise the photo will lack the proper contrast and appear flat or dull.
So instead of squinting, you need to override your meter and adjust your camera in the other direction. You actually need to let in more light than your meter suggests so that the white object will appear white. That's the secret. More light in your exposure equals brighter tones.
I'll talk about calibrating your camera later on, but most whites fall around two stops over the 18% gray that your meter suggests. So you can meter a white and open approximately two stops (again, test your camera to be sure) to achieve a good white that still has a minimum of detail.
Exposure - Dark Subjects
Dark subjects work on the same principle as light subjects, but in reverse. In order to stay dark, they need less light, less exposure. So if you're metering off a black object, you'll need to close down to a smaller aperture or else raise your shutter speed.
A good black will fall around two and a half stops under the 18% gray that your meter suggests. Again, test your camera to be sure.
Conclusion
So to re-cap, with bright subjects you need to overexpose from your meter's reading. Bright objects need more light so they can remain bright. And in the opposite direction, dark subjects need to be underexposed from your meter reading. Dark objects need less light so they can remain dark.
Once you are able to visualize that principle of light, you're on your way to understanding exposure and having great exposures in your photography
www.zibtips.com
How Meters Work
Exposure
The correct exposure is essential to the quality of your image.
Some people follow the philosophy "Fix it in the computer." But that should be the last resort. Fixing a photo on the computer is not the magical answer that it has been made out to be. In fact, every tonal adjustment you make to your photo on the computer, making it lighter or darker, etc., reduces the amount of pixel data in your photo. So as you're "saving" your image, you're actually degrading it, throwing away data. Best to get it right in camera.
Meters
The meter in your camera measures the light in your scene telling you or your camera what shutter speed and aperture settings will provide the proper exposure.
It's important to know how the meter sees and what it is trying to do. A meter takes in all of the tones in the scene (light and dark) and averages those tones to compute an exposure setting. The meter is finding an average, aiming for an 18% gray tone. And that's great for most scenes, where light and dark tones average into gray, such as the photo below.
.jpg)
Types of Metering
Advances in camera metering systems over the years have been impressive. Still, it's important to know what your meter is thinking and how various meters see the light.
Most cameras will read the light in the scene by measuring the brightness of light reflected through the lens. For more accurate light readings, handheld meters can tell you how bright the ambient light is in any environment. Here is a quick breakdown of typical modern metering options:
Matrix or Evaluative Metering — This type of metering breaks the scene up into multiple segments which are analyzed for brightness and then compared to a pre-programmed database of thousands of typical photographic scenes. All of this happens instantaneously. Matrix/Evaluative metering modes are very accurate and useful especially in situations where you're using an auto-exposure mode or when the light is changing frequently. While not perfect, they come close in most situations.
Spot Metering — Spot meters read the brightness of a single spot in the middle of the frame, allowing you to take a precise reading of a small area. Spot metering is very handy when you're shooting in manual modes and have the time for extreme precision.
Incident Metering — Handheld meters provide highly accurate light measurements by metering the ambient light in a scene. That is, they tell you exactly what settings to use on your camera by telling you exactly how bright it is. There are drawbacks to using a handheld meter, including the cost of the meter. And for an accurate reading, the meter has to be in the same light as your subject. This can be problematic in a situation like a concert, where access to the stage is often controlled.
Latitude
Correct exposure settings are essential for serious photography. While your eyes are capable of seeing detail over a wide latitude, film and digital cameras have a much tighter latitude. If you expose for the sunlight, things in the shade will appear dark. If you expose for the shade, everything in the sunlight will be too bright. There are techniques to balance the light in such situations, such as using fill-flash.
But it bears repeating: Setting the correct exposure is essential to the quality of your image.
www.zibtips.com
The correct exposure is essential to the quality of your image.
Some people follow the philosophy "Fix it in the computer." But that should be the last resort. Fixing a photo on the computer is not the magical answer that it has been made out to be. In fact, every tonal adjustment you make to your photo on the computer, making it lighter or darker, etc., reduces the amount of pixel data in your photo. So as you're "saving" your image, you're actually degrading it, throwing away data. Best to get it right in camera.
Meters
The meter in your camera measures the light in your scene telling you or your camera what shutter speed and aperture settings will provide the proper exposure.
It's important to know how the meter sees and what it is trying to do. A meter takes in all of the tones in the scene (light and dark) and averages those tones to compute an exposure setting. The meter is finding an average, aiming for an 18% gray tone. And that's great for most scenes, where light and dark tones average into gray, such as the photo below.
.jpg)
Types of Metering
Advances in camera metering systems over the years have been impressive. Still, it's important to know what your meter is thinking and how various meters see the light.
Most cameras will read the light in the scene by measuring the brightness of light reflected through the lens. For more accurate light readings, handheld meters can tell you how bright the ambient light is in any environment. Here is a quick breakdown of typical modern metering options:
Matrix or Evaluative Metering — This type of metering breaks the scene up into multiple segments which are analyzed for brightness and then compared to a pre-programmed database of thousands of typical photographic scenes. All of this happens instantaneously. Matrix/Evaluative metering modes are very accurate and useful especially in situations where you're using an auto-exposure mode or when the light is changing frequently. While not perfect, they come close in most situations.
Spot Metering — Spot meters read the brightness of a single spot in the middle of the frame, allowing you to take a precise reading of a small area. Spot metering is very handy when you're shooting in manual modes and have the time for extreme precision.
Incident Metering — Handheld meters provide highly accurate light measurements by metering the ambient light in a scene. That is, they tell you exactly what settings to use on your camera by telling you exactly how bright it is. There are drawbacks to using a handheld meter, including the cost of the meter. And for an accurate reading, the meter has to be in the same light as your subject. This can be problematic in a situation like a concert, where access to the stage is often controlled.
Latitude
Correct exposure settings are essential for serious photography. While your eyes are capable of seeing detail over a wide latitude, film and digital cameras have a much tighter latitude. If you expose for the sunlight, things in the shade will appear dark. If you expose for the shade, everything in the sunlight will be too bright. There are techniques to balance the light in such situations, such as using fill-flash.
But it bears repeating: Setting the correct exposure is essential to the quality of your image.
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