Monday, January 28, 2013
Introduction
While I hope to one day expand this blog to be more general and comprehensive, for lack of time it will now serve to help just one person who has bought a Nikon D5100. I'm sure it could be helpful to others, but for the time being it's a very directed audience.
Sunday, January 27, 2013
Point 1: Zoom (Focal Length)
Intro
While it seems simple, understanding the zoom lens on your camera makes a big difference in how you can make your shots turn out. The common understanding of a zoom lens is that it lets you make objects farther away look larger in pictures. That's true, but it's really doing much more than that.
Terminology
Zoom lenses are typically referred to by four different numbers such as a typical 18-55mm f/3.5-5.6. We'll get to the f/3.5-5.6 numbers later. For now, we're interested in the 18-55mm number. This is the zoom range of the lens, also know as focal length. At it's widest or "zoomed out," the focal length is 18mm. At it's tightest or "zoomed in," the focal length is 55mm.
18-55 is generally considered a "normal" zoom range for these types of cameras. Anything with smaller numbers (eg 10-24mm) is typically considered a "wide-angle" while larger numbers such as a 55-300mm are typically considered "telephoto."
Compression of Field and Field of View
While zooming in or out does make the object you're focusing on appear larger or smaller, the rest of the scene changes too. Specifically, how near or far away objects appear to each other changes and how much of the background you can see changes.
Let's look at an example.
When zoomed all the way out to 18mm, the statue of Emily Dickinson can fill the frame from top to bottom. You can see a good expanse of background behind her -- you have a large/wide field of view. But also note how the trees and buildings in the background look far away. You can just barely make out a building over her right shoulder. When zoomed out, the background is not very compressed. In fact, we're zoomed out far enough that the background seems expanded -- objects in the background appear farther away and smaller than they really are.
The building in the back right appears to be almost smaller than the statue. This presents the statue as being larger than it actually is and almost dynamic. When zoomed out, whatever is closest to the camera seems larger than objects farther away. This is a great technique to use with subjects that are otherwise boring or don't stand out from the background - zoom out, get closer, and fill the frame. However, be careful when taking a picture of a person at eye level zoomed out. Their head can appear larger and their body smaller as it is farther away.
Good For:
- Sports, pet, or other subject shots where you want the subject to be the true focus of the image
- Shots where you want to "set" the subject in a distant background by compressing it forward (graduation shot with student on a field and a building in the distance and you make the building look larger)
- Portrait shots that provide a slightly more pleasing compression than a normal view
Bad For:
- Composition-wise it's hard to find a drawback, but there are other concerns (see aperture and shutter speed).
Personal Notes
My best suggestion is to set a zoom at a focal length then walk around and take pictures. Force yourself to move versus changing the focal length. It gives you a great appreciation for some of the things that can be done. Wide-angle shots are the most under used by people who first get a zoom lens.
Technical Notes
There are a couple BIG technical notes here.
First, zoom lenses are difficult to design. As such, you may experience some image issues, although none are likely to be noticeable unless you look. For instance, when zoomed out you may see some curvature to the image (barrel distortion) and the edges may be darker than the middle (fall off or vignette). Zoomed in you may see the opposition distortion (pincushion) and also fall off/vignette.
Second, and this is the big one, focal lengths are sometimes referred to by "35mm equivalent" numbers. Only top end digital cameras have sensors as large as 35mm film was. These are often referred to as "full-frame" cameras. Most DSLRs have sensors about 2/3rds the size of a "full-frame" sensor and are referred to as APS-C size.
For the same field of view and compression of background, a smaller sensor requires a smaller focal length. So, APS-C camera lens focal lengths are about 2/3rds that of full-frame (FF) camera focal lengths. But, because so many photographers grew up with 35mm film, those focal lengths are standard in their minds. They may refer to the kit 18-55mm lens as a 27-82 (18-55 X 1.5).
This obviously breeds confusion, but it does allow for a standard. Few camera companies use exactly the same size sensor, so referring to 35mm equivalent focal lengths allows easy comparison.
While it seems simple, understanding the zoom lens on your camera makes a big difference in how you can make your shots turn out. The common understanding of a zoom lens is that it lets you make objects farther away look larger in pictures. That's true, but it's really doing much more than that.
Terminology
Zoom lenses are typically referred to by four different numbers such as a typical 18-55mm f/3.5-5.6. We'll get to the f/3.5-5.6 numbers later. For now, we're interested in the 18-55mm number. This is the zoom range of the lens, also know as focal length. At it's widest or "zoomed out," the focal length is 18mm. At it's tightest or "zoomed in," the focal length is 55mm.
18-55 is generally considered a "normal" zoom range for these types of cameras. Anything with smaller numbers (eg 10-24mm) is typically considered a "wide-angle" while larger numbers such as a 55-300mm are typically considered "telephoto."
Compression of Field and Field of View
While zooming in or out does make the object you're focusing on appear larger or smaller, the rest of the scene changes too. Specifically, how near or far away objects appear to each other changes and how much of the background you can see changes.
Let's look at an example.
When zoomed all the way out to 18mm, the statue of Emily Dickinson can fill the frame from top to bottom. You can see a good expanse of background behind her -- you have a large/wide field of view. But also note how the trees and buildings in the background look far away. You can just barely make out a building over her right shoulder. When zoomed out, the background is not very compressed. In fact, we're zoomed out far enough that the background seems expanded -- objects in the background appear farther away and smaller than they really are.
The building in the back right appears to be almost smaller than the statue. This presents the statue as being larger than it actually is and almost dynamic. When zoomed out, whatever is closest to the camera seems larger than objects farther away. This is a great technique to use with subjects that are otherwise boring or don't stand out from the background - zoom out, get closer, and fill the frame. However, be careful when taking a picture of a person at eye level zoomed out. Their head can appear larger and their body smaller as it is farther away.
For the second shot I stepped back and zoomed in about half way to 35mm. This is close to what the eye is used to seeing (the eye has a focal length right around 30mm measured on this camera). Note that the statue covers about the same portion of the picture since I stepped back.
You can see right away that less background is visible. The building on the right of the picture is half cut off, and you can see less of the tree on the left of the picture. The field of view is narrower.
The background is also more compressed. Now the buildings and trees in the background appear to be much closer to the statue. The building on the right that appeared small now looks appropriately sized. By using this focal length, the image appears as expected with objects the appropriate distance to each other and in the proper proportions. It's a very useful length to shoot at regardless of subject.
For this shot I stepped back even farther and took the picture at 55mm or all the way "zoomed in." The field of view is now very narrow. The building on the right is almost out of frame.
The background is also very compressed. You can see how the tree from the first shot that looked so far away now appears to be very close to the statue -- almost as though the branches are over her head. You can also clearly see the building to her right (left of the picture) now as it appears much closer. The building that was small in the first shot is now almost out of frame.
Zooming in primarily helps put the emphasis of the image on the object, not the background. This can be very useful if there is a distracting background like a crowd. Alternatively, you can zoom in to bring the background in to play. Had we used a telephoto lens at say 200mm we could have made the building on the left side of this picture look even larger and framed the statue against that.
In Use
If you can't get close to a subject you may be forced to zoom in, or when you can't stand far enough back from a subject you may have to zoom out. But, if you are able to compose the shot as you'd like, try setting the focal length and moving your feet to get the appropriate shot. Here are some general tips for when zoomed in or zoomed out might be helpful.
Wide-Angle/Zoomed Out/Short Focal Length/18mm-
Good For:
- Landscape shots where you want to capture a wide angle of view
- Still life shots where you want to create "tension" by making the object look larger than the background
Bad For:
- Portraits or family shots as people can look distorted
Normal/Medium Zoom/Normal Focal Length/30-35mm
Good For:
- Almost any shot as it provides a similar image to the eye
- "Set it and forget it" and then moving your feet
- Portraits where you want a similar to real life look
Bad For:
- Shots where there is little inherent excitement and wide angle tension or background compression would help
Telephoto/Zoomed in/Long Focal Length/55mm+
Good For:
- Sports, pet, or other subject shots where you want the subject to be the true focus of the image
- Shots where you want to "set" the subject in a distant background by compressing it forward (graduation shot with student on a field and a building in the distance and you make the building look larger)
- Portrait shots that provide a slightly more pleasing compression than a normal view
Bad For:
- Composition-wise it's hard to find a drawback, but there are other concerns (see aperture and shutter speed).
Personal Notes
My best suggestion is to set a zoom at a focal length then walk around and take pictures. Force yourself to move versus changing the focal length. It gives you a great appreciation for some of the things that can be done. Wide-angle shots are the most under used by people who first get a zoom lens.
Technical Notes
There are a couple BIG technical notes here.
First, zoom lenses are difficult to design. As such, you may experience some image issues, although none are likely to be noticeable unless you look. For instance, when zoomed out you may see some curvature to the image (barrel distortion) and the edges may be darker than the middle (fall off or vignette). Zoomed in you may see the opposition distortion (pincushion) and also fall off/vignette.
Second, and this is the big one, focal lengths are sometimes referred to by "35mm equivalent" numbers. Only top end digital cameras have sensors as large as 35mm film was. These are often referred to as "full-frame" cameras. Most DSLRs have sensors about 2/3rds the size of a "full-frame" sensor and are referred to as APS-C size.
For the same field of view and compression of background, a smaller sensor requires a smaller focal length. So, APS-C camera lens focal lengths are about 2/3rds that of full-frame (FF) camera focal lengths. But, because so many photographers grew up with 35mm film, those focal lengths are standard in their minds. They may refer to the kit 18-55mm lens as a 27-82 (18-55 X 1.5).
This obviously breeds confusion, but it does allow for a standard. Few camera companies use exactly the same size sensor, so referring to 35mm equivalent focal lengths allows easy comparison.
Saturday, January 26, 2013
Point 2: Exposure
Intro
When your camera is set to "automatic" it is handling all the technical factors for you. The magic boxes that are DSLRs nowadays are very adept at getting shots right in automatic. However, there are lots of things that you can make the camera do that it may never choose to do when left to its own devices. In fact, the true beauty of a DSLR is that you can take control of everything and alter the shot as you like.
The following sections have details on how you can adjust a variety of settings to get the most out of your camera, but there are a few terms that should be cleared up and some notes on how your camera operates.
Terminology
The most important term to know when adjusting a shot is exposure. Exposure determines how brightly lit a shot is. If a shot is under-exposed it is too dark, possibly to the point that some parts of the image are black without any details (shadow). If a shot is over-exposed it is too bright, possibly to the point that some parts of the image are white without any details (highlight). Regardless of anything else, if a shot is too far over or under exposed, it's junk.
Exposure is measured in whole or fractional "stops." There is no real measuring point that a bright, sunny day is # stops, it is simply relative to itself. So, if while taking a picture of people in sunny field a cloud rolls in, it may change the brightness by -1 stop. It's helpful to know this measurement unit as adjustments to the camera can be measured in stops of how much light you are gaining or losing.
Exposure is balanced by three separate factors:
1) How sensitive the image sensor is to light (ISO)
2) How much light the lens lets through (aperture)
3) How long the sensor has light shining on it (shutter speed)
While you can manually set each of these factors to determine exposure on your own, the following sections will look at each one individually and let the camera decide the best of the remaining settings.
Friday, January 25, 2013
Point 3: Shutter Speed
Intro
On the one hand, the shutter of a camera is used to set exposure by determining how long the sensor is exposed to light for any given shot. On the one hand, the shutter also determines how much movement is captured in an image. For images with fast moving objects you need a fast/short shutter speed so that the images don't appear blurred. In other situations you may slow/long shutter speed so that motion is apparent.
Terminology
Shutter speeds are measured in fractional seconds. However, when adjusting shutter speed cameras adjust them in increments to be related to fractions of a stop. For instance, if you were to increase the shutter speed from 1/50th of a second it would likely go to 1/60th of a second -- one third of a stop of light less. Moving again from 1/60th of a second it would go to 1/80th of a second -- another third of a stop.
Always, the faster the shutter speed, the less light available for the picture. The fastest shutter speeds on most cameras is 1/4000 of a second which is fast enough for almost any situation. Professional cameras typically go up to 1/8000. Shutter speeds can be as slow as you like though, even measured in minutes for late night shots.
Shutter speed is directly related to blur, which may come in 2 forms. First, there is motion blur from an object moving while the picture is being taken. Simply put, the faster the object is moving the faster the shutter speed needs to be. To my knowledge, there is no rule of thumb for a speed:motion blur equivalence. From my experience, you want about 1/50th or faster for walking/talking/party etc. For running or fast movement, 1/300th or faster.
The second blur is camera shake. The longer the focal length of the shot (the more zoomed in), the more camera shake is apparent. There is a rule of thumb in this case, but it relates to 35mm equivalent focal lengths. The rule is the shutter speed should be no shorter than one over the 35mm equivalent focal length to avoid camera shake blur. So, if you're shooting at 55mm that's 82mm equivalent you should be at 1/80th or faster or your image may be blurry even if there is no motion.
Vibration Reduction (aka image stabilization) is a way some lenses have of reducing camera shake. They're quite good, but not infallible. Typically, VR allows 1 to 2 stops slower shutter speeds without worrying about camera shake. So, at 55mm you may be able to shoot around 1/20th of a second without camera shake (although that's pushing it, honestly).
Shutter Speed
In order to manually set shutter speed, you'll need to change your camera's PASM dial to "S". The "S" stands for shutter priority. In other words, the camera will set everything for you based on the shutter speed you select. This is a great way to be able to control one aspect of your shot while the camera manages the rest.
I'll use an example of a fountain that has a very slow flow rate. Many fountains, streams, and waterfalls flow faster than this, but it will serve as a good comparison.
Here is the pool of water at 1/250th.
And again at 1/2. Notice how the foot of the statue is still relatively sharp (there is some camera shake if you zoom in), but even the reflections are now blurred.
In Use
Typically you will always want to use a shutter speed that is at least one over your focal length. That is a great rule of thumb for taking pictures of people and scenery. Nothing is more frustrating that the perfect shot that turns out blurry because the shutter speed was too slow.
When you get to a dimly lit room and don't want a flash, you may want to turn your PASM dial to "S" so that you can set a minimum shutter speed. Also, you may have a menu setting that allows you to set a minimum shutter speed that the camera won't go below even in automatic.
When you're trying to freeze action like a runner, always give yourself room if you can. If you're shooting at 200mm, 1/300th may be good, but if it's bright enough take 1/500th or 1/1000th if you can. Especially at very long focal lengths, very slight movements can introduce annoying camera shake.
If you're going around nature or water, take a tripod! That will allow you to set very low shutter speeds that can create surreal pictures, or just set the speed low enough that you can catch the motion of water without camera shake.
Trade-Offs
The faster the shutter speed you use, the less exposed the shot is. So, fast shutter speeds are easy on bright days, but indoors it's difficult to get a very fast shutter speed and still expose the shot. High ISO, large apertures, and flashes can help.
On the other hand, getting to slow shutter speeds may not be possible on bright days. The fountain shots above were only possible because it was a dark, overcast day. Lens filters can actually reduce light to allow for longer shutter speeds.
Technical Notes
If you use a tripod, TURN VR OFF. VR can over-correct if it's on a tripod and introduce shake.
On the one hand, the shutter of a camera is used to set exposure by determining how long the sensor is exposed to light for any given shot. On the one hand, the shutter also determines how much movement is captured in an image. For images with fast moving objects you need a fast/short shutter speed so that the images don't appear blurred. In other situations you may slow/long shutter speed so that motion is apparent.
Terminology
Shutter speeds are measured in fractional seconds. However, when adjusting shutter speed cameras adjust them in increments to be related to fractions of a stop. For instance, if you were to increase the shutter speed from 1/50th of a second it would likely go to 1/60th of a second -- one third of a stop of light less. Moving again from 1/60th of a second it would go to 1/80th of a second -- another third of a stop.
Always, the faster the shutter speed, the less light available for the picture. The fastest shutter speeds on most cameras is 1/4000 of a second which is fast enough for almost any situation. Professional cameras typically go up to 1/8000. Shutter speeds can be as slow as you like though, even measured in minutes for late night shots.
Shutter speed is directly related to blur, which may come in 2 forms. First, there is motion blur from an object moving while the picture is being taken. Simply put, the faster the object is moving the faster the shutter speed needs to be. To my knowledge, there is no rule of thumb for a speed:motion blur equivalence. From my experience, you want about 1/50th or faster for walking/talking/party etc. For running or fast movement, 1/300th or faster.
The second blur is camera shake. The longer the focal length of the shot (the more zoomed in), the more camera shake is apparent. There is a rule of thumb in this case, but it relates to 35mm equivalent focal lengths. The rule is the shutter speed should be no shorter than one over the 35mm equivalent focal length to avoid camera shake blur. So, if you're shooting at 55mm that's 82mm equivalent you should be at 1/80th or faster or your image may be blurry even if there is no motion.
Vibration Reduction (aka image stabilization) is a way some lenses have of reducing camera shake. They're quite good, but not infallible. Typically, VR allows 1 to 2 stops slower shutter speeds without worrying about camera shake. So, at 55mm you may be able to shoot around 1/20th of a second without camera shake (although that's pushing it, honestly).
Shutter Speed
In order to manually set shutter speed, you'll need to change your camera's PASM dial to "S". The "S" stands for shutter priority. In other words, the camera will set everything for you based on the shutter speed you select. This is a great way to be able to control one aspect of your shot while the camera manages the rest.
I'll use an example of a fountain that has a very slow flow rate. Many fountains, streams, and waterfalls flow faster than this, but it will serve as a good comparison.
For our first statue shot, the shutter speed is set to 1/1000th of a second. The shot is well exposed and well composed (good enough at least), but the shutter speed was set so high that the fountain that typically looks like a stream of water now looks like droplets.
The second shot was reduced to 1/160th of a second (2 and 2/3rd stops longer than 1/1000). Again, at 1/160th the water distracts from the picture as it looks choppy.
At 1/80th (1 stop longer than 1/160) the water is beginning to look more natural. While there are still droplets, the water at least looks like it is flowing. Without lens VR or with people in the shot, this or 1/50th is about as slow as I would want to go. It would give a nice balance of water flowing but assurance that the shot will be blur free.
Now at 1/20th (2 stops longer than 1/80) individual droplets are no longer visible. However, you can still make out some break in each of the streams. While VR is preventing this shot from being blurred from camera shake, people would have to hold pretty still to not get any blur from their movements.
This shot is at 1/10th (1 stop longer than 1/20) of a second. VR and a steady hand have kept camera shake blur away, but I definitely would not have shot this slowly with people involved. The water now has a decided flow to it, and even the pool around the fountain is beginning to look less crisp.
Now down to 1/5th of a second (1 stop longer than 1/10th) any breaks in the streams are gone. The image is still relatively blur free, but if you zoom in very tightly you'll see the start of some blur from camera shake.
This shot was at 1/2 seconds -- a full stop and a third longer than 1/5 of a second. At this point the streams look fully blurred and even the pool around it seems blurred from the ripples of water. This clearly presents the image of a flowing fountain and moving water.
Here is the pool of water at 1/250th.
And again at 1/2. Notice how the foot of the statue is still relatively sharp (there is some camera shake if you zoom in), but even the reflections are now blurred.
In Use
Typically you will always want to use a shutter speed that is at least one over your focal length. That is a great rule of thumb for taking pictures of people and scenery. Nothing is more frustrating that the perfect shot that turns out blurry because the shutter speed was too slow.
When you get to a dimly lit room and don't want a flash, you may want to turn your PASM dial to "S" so that you can set a minimum shutter speed. Also, you may have a menu setting that allows you to set a minimum shutter speed that the camera won't go below even in automatic.
When you're trying to freeze action like a runner, always give yourself room if you can. If you're shooting at 200mm, 1/300th may be good, but if it's bright enough take 1/500th or 1/1000th if you can. Especially at very long focal lengths, very slight movements can introduce annoying camera shake.
If you're going around nature or water, take a tripod! That will allow you to set very low shutter speeds that can create surreal pictures, or just set the speed low enough that you can catch the motion of water without camera shake.
Trade-Offs
The faster the shutter speed you use, the less exposed the shot is. So, fast shutter speeds are easy on bright days, but indoors it's difficult to get a very fast shutter speed and still expose the shot. High ISO, large apertures, and flashes can help.
On the other hand, getting to slow shutter speeds may not be possible on bright days. The fountain shots above were only possible because it was a dark, overcast day. Lens filters can actually reduce light to allow for longer shutter speeds.
Technical Notes
If you use a tripod, TURN VR OFF. VR can over-correct if it's on a tripod and introduce shake.
Thursday, January 24, 2013
Point 4: Film Speed (ISO)
Intro
Just like "film speed," your camera's sensor has variable sensitivity to light. In automatic modes the camera manages this for you, and it tends to lean towards to conservative to get you the best picture. However, situations may arise such as dark rooms where you don't want to use a flash where you want to overrule the camera.
Terminology
ISO is a leftover term from film cameras, but it still refers to the sensor "speed." Typically cameras have a base ISO of 100 or 200, although some go as low as 50. Manufacturers are always trying to produce higher ISO. Most cameras have sensors that go to ISO 1600 or 3200 and then have "expanded" settings (High 1 and High 2) to 6400 and 12,800. The expanded setting is truly just software manipulation after the picture is taken. Very top end cameras may go as high as ISO 102,400 or ISO 204,800.
The higher the ISO the more "noise" in a shot and the less clarity, color depth, and dynamic range. Noise is apparent by patterns of dots. This can be somewhat pleasant like an old film grain, or it can be harsh like bands of color. Noise is most prevalent in the darker areas of high ISO shots. Cameras do have noise reduction which can mitigate most noise, but that it turn reduces the clarity or sharpness of a shot.
Color depth and dynamic range are also reduced with higher ISO. Color depth is the ability to produce a range of colors. At higher ISOs colors tend to become less true and clarity of the shot is also reduced as similar colors begin to blend together.
Dynamic range is the range of dark to bright that can be capture by a sensor. DSLRs typically have very good dynamic range and can capture a photo with shadow and highlight. However, as ISO increase shadows turn black more quickly and highlights turn white more quickly -- detail is lost.
Choosing ISO
As said above, the camera will typically choose ISO for you. You can also normally set the max ISO you find acceptable for automatic use through the menu system. However, you may find a time when you want to push the max ISO above your normal thresholds to capture dark scenes or so that you can use a higher shutter speed or smaller aperture.
While not really a situation I would use a high ISO, this first shot was taken at High 2 or 12,800 ISO equivalent. With very good lighting, the camera has done a good job of mitigating some of the negative effects. However, if you enlarge the image and compare it to others you'll note several points.
First, the color of the black sign isn't exactly true -- it's more yellow than it should be. Also, the plants in the bottom right corner are too brown. The mortar between the bricks isn't detailed and the plaque looks grainy.
The second shot is at ISO 1600. The differences are immediately apparent. The plague is a better black; the bush in the bottom right is the appropriate green, the mortar has more detail, and the text is less "noisy." There are still flaws in the color and clarity of the image, but they are much harder to find -- the camera has done a great job at minimizing them.
This was taken at ISO 400. While there are differences to ISO 1600, they are hard to determine. I would say the colors are a little more true -- more blue in them. Slightly less noise. But, in all it's hard to tell.
This shot is at ISO 100. The difference to 400 is minimal if apparent at all. However, that speaks to the quality of the sensor. You have to be very technical to find the difference between ISO 100 and ISO 400. However, this shot is clearly noise free, offers true color reproduction, and has lots of detail.
In Use
Determining your camera's ISO setting is important at first, then determine what your comfort level is for high ISO shots. In some cases, like an indoor sporting event, high ISO may be the only way to get the shutter speed you need to get a shot. So, it's high ISO or nothing. In other cases, you may be able to use a flash to compensate for a lack of light.
Once you've determined your tolerance for high ISO shots and know how to set it, use it appropriately. ISO 800 is a good trade-off between quality and range of exposure. However, that's too much on a bright day and not enough in a church.
ISO 100 - 400
- Great for portraits and landscapes. You get the absolute best color and quality
ISO 800 & 1600
- Good compromise ISOs. You're not giving up too much in quality, especially at 800. Good for indoors and not using a flash
ISO 3200
- This is an "if I must" setting. There is definitely a quality hit at this point, but the shots are still decent.
ISO 6400 & 12800
- Really, these are last resort settings. You'll get the shot and it might look good on a screen. But, you'll give up a lot, especially at the 12800 setting.
Just like "film speed," your camera's sensor has variable sensitivity to light. In automatic modes the camera manages this for you, and it tends to lean towards to conservative to get you the best picture. However, situations may arise such as dark rooms where you don't want to use a flash where you want to overrule the camera.
Terminology
ISO is a leftover term from film cameras, but it still refers to the sensor "speed." Typically cameras have a base ISO of 100 or 200, although some go as low as 50. Manufacturers are always trying to produce higher ISO. Most cameras have sensors that go to ISO 1600 or 3200 and then have "expanded" settings (High 1 and High 2) to 6400 and 12,800. The expanded setting is truly just software manipulation after the picture is taken. Very top end cameras may go as high as ISO 102,400 or ISO 204,800.
The higher the ISO the more "noise" in a shot and the less clarity, color depth, and dynamic range. Noise is apparent by patterns of dots. This can be somewhat pleasant like an old film grain, or it can be harsh like bands of color. Noise is most prevalent in the darker areas of high ISO shots. Cameras do have noise reduction which can mitigate most noise, but that it turn reduces the clarity or sharpness of a shot.
Color depth and dynamic range are also reduced with higher ISO. Color depth is the ability to produce a range of colors. At higher ISOs colors tend to become less true and clarity of the shot is also reduced as similar colors begin to blend together.
Dynamic range is the range of dark to bright that can be capture by a sensor. DSLRs typically have very good dynamic range and can capture a photo with shadow and highlight. However, as ISO increase shadows turn black more quickly and highlights turn white more quickly -- detail is lost.
Choosing ISO
As said above, the camera will typically choose ISO for you. You can also normally set the max ISO you find acceptable for automatic use through the menu system. However, you may find a time when you want to push the max ISO above your normal thresholds to capture dark scenes or so that you can use a higher shutter speed or smaller aperture.
While not really a situation I would use a high ISO, this first shot was taken at High 2 or 12,800 ISO equivalent. With very good lighting, the camera has done a good job of mitigating some of the negative effects. However, if you enlarge the image and compare it to others you'll note several points.
First, the color of the black sign isn't exactly true -- it's more yellow than it should be. Also, the plants in the bottom right corner are too brown. The mortar between the bricks isn't detailed and the plaque looks grainy.
The second shot is at ISO 1600. The differences are immediately apparent. The plague is a better black; the bush in the bottom right is the appropriate green, the mortar has more detail, and the text is less "noisy." There are still flaws in the color and clarity of the image, but they are much harder to find -- the camera has done a great job at minimizing them.
This was taken at ISO 400. While there are differences to ISO 1600, they are hard to determine. I would say the colors are a little more true -- more blue in them. Slightly less noise. But, in all it's hard to tell.
This shot is at ISO 100. The difference to 400 is minimal if apparent at all. However, that speaks to the quality of the sensor. You have to be very technical to find the difference between ISO 100 and ISO 400. However, this shot is clearly noise free, offers true color reproduction, and has lots of detail.
In Use
Determining your camera's ISO setting is important at first, then determine what your comfort level is for high ISO shots. In some cases, like an indoor sporting event, high ISO may be the only way to get the shutter speed you need to get a shot. So, it's high ISO or nothing. In other cases, you may be able to use a flash to compensate for a lack of light.
Once you've determined your tolerance for high ISO shots and know how to set it, use it appropriately. ISO 800 is a good trade-off between quality and range of exposure. However, that's too much on a bright day and not enough in a church.
ISO 100 - 400
- Great for portraits and landscapes. You get the absolute best color and quality
ISO 800 & 1600
- Good compromise ISOs. You're not giving up too much in quality, especially at 800. Good for indoors and not using a flash
ISO 3200
- This is an "if I must" setting. There is definitely a quality hit at this point, but the shots are still decent.
ISO 6400 & 12800
- Really, these are last resort settings. You'll get the shot and it might look good on a screen. But, you'll give up a lot, especially at the 12800 setting.
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