MarkBarbieri
Semi-retired
- Joined
- Aug 20, 2006
- Messages
- 6,172
Image stabilization (IS, VR, or whatever) gets a lot of discussion. High ISO (with low noise) gets very little discussion. I wonder if people realize that there is considerable overlap between the two. Given a choice between a camera/lens with 2-3 stop image stabilization or one with a 2-3 stop useable ISO advantage, which is better and why?
One of the major enemies to getting sharp pictures is motion. If anything moves while the picture is being taken, the result is blur. The motion can come from the camera or the subject. It can be because the camera is on something moving (like a Disney ride), because the photographer is not holding the camera perfectly still, or because the all or part of the subject is moving.
One way to counter motion in photographs is to take the picture faster. If you take a picture at a shutter speed of 1/8000 of a second, that means that you will only capture the motion that occurs during that 1/8000 time duration (sort of). With a shutter speed that fast, it rarely matters if the photographer, the camera, or the subject is moving because it won't move very far during that time.
At the opposite extreme, if you take a picture with a shutter speed of 30 minutes, there is a very good chance that even "non-moving" subjects are going to have motion blur. The stars and moon, while apparently motionless, will visibly move across part of the sky during this time. The branches and leaves on trees will sway. All but the most still water will ripple.
Another issue, in addition to time, is magnification. The more you magnify (or zoom in), the more you magnify any motion. This "magnification" can take many forms - zooming in, walking closer, or using a smaller sensor. In the end, all that matters is the amount of the motion across your pixels. Ideally, if you want to freeze something, it should start and stop the picture on the same pixel. The more pixels that it moves across during the exposure, the more motion blur you'll see in your image.
There are several guidelines that have been developed over the years to help us pick a reasonable shutter speed. The most commonly heard is the inverse focal length rule. That's a complicated sounding name that basically means that your shutter speed should be equivalent to how zoomed in you are. For example, if you are using a 30mm lens, you should try to have a 1/30 second shutter speed. If you are using a 300mm lens, you are magnifying things more and should use a 1/300 second shutter speed.
The inverse focal length rule was developed back in the 35mm film days. For equivalent results, you should factor in your sensor size. Just as your 100mm lens on your camera might have the same field of view of a 150mm lens on a film camera, you should aim for a 1/150s shutter speed instead of a 1/100 second shutter speed. The reason is that it isn't the focal length that is important in determining how quick you need to be - it's the overall magnification of the system.
The inverse focal length rule is designed to compensate for a typical photographer hand-holding a typical lens and wanting typical results. It doesn't deal with subject motion. It doesn't guarantee perfectly sharp results. It doesn't apply to unusually steady or shaky people. It's just a general guideline.
I've never really seen a good rule for determine how fast a shutter speed is required when your subject is moving. It depends on a lot of different things - how fast the subject is moving, how close the subject is, how magnified the subject is, and what direction (relative to the camera) the subject is moving. The important thing to consider is how much the subject is moving around in the picture. If it is coming towards or away from you, it won't move across as many pixels if it is moving from side to side. If it is close or highly magnified, a little motion will produce a large effect. As a very, very, very general rule, 1/250s is usually good enough to freeze something moving towards or away from you and 1/2000s is usually good enough to freeze something moving from one side of the picture towards another.
So what happens if you can't get a shutter speed fast enough? You could open the aperture wider. That's why people pay so much money for "fast" lenses. They can open really wide so that you can get a faster shutter speed. That also makes your depth-of-field shallower, which might not be desired. Also, lenses tend not to perform as well when they are opened as wide as they can be.
You can add more light. That works great in the studio when you control the lighting, but not as well outside. Still, if the scene is dark, adding flash can be the difference between a blurring shot and an acceptable shot. Adding light with a flash is great for stopping motion because the light from the flash is usually present for a very short period of time (often less than 1/1000 of a second).
Assuming that you don't want to or cannot open your lens wider or add more light, you've still got a few options left - a tripod, image stabilization, and increasing ISO. A tripod is the ideal answer when the problem is camera movement. A good tripod can virtually eliminate camera movement. To get the best results from a tripod, you want to trigger the shutter without touching the tripod. You can do that with a wired or wireless remote or with the timer mode on your camera.
With shutter speeds between about 1/60s and 2 seconds, it can also help if you lock up your camera's mirror. When you look through the viewfinder or an SLR, you are seeing light that has gone through the lens and is reflected up to the viewfinder by a mirror. When you take a picture, the mirror swings up and out of the way so that the light can get to the sensor. The motion of the mirror causes a little vibration within the camera that can blur your pictures. Locking up your mirror before the shot prevents that problem. You don't need to do it for faster pictures because there isn't time for the vibration to cause a problem. You don't need to do it for longer pictures because the vibration dies down so quickly that it doesn't have a noticeable impact on the picture.
Using a tripod only helps stabilize your camera. It doesn't do anything to help with subject motion (unless your subject stops to look at your tripod).
An image stabilizer is sort of like a tripod in that it helps stabilize your camera. It's much more convenient to use, but it isn't nearly as effective. A camera on a decent tripod will always outperform a handheld camera using an image stabilizer. The stabilizer is for use when you can't or won't use a tripod. Like a tripod, it only helps deal with camera motion and not subject motion.
Stabilizers are often rated in how many "stops" they are good for. One stop is essentially a doubling of the shutter speed. So if you are using a lens that you get good shots with hand held at 1/60s, a stabilizer that gave your two extra stops would allow you to use the lens at 1/15s. The first extra stop doubles the time from 1/60s to 1/30s (remember, we're using fractions of a second, so longer times mean smaller numbers on the bottom) and the second extra stop doubles the time from 1/30s to 1/15s.
Stabilizers don't really give you "x" number of extra stops. We rate them that way because it's kind of close and it's easy. It helps to understand how stabilizers work so that you can see how they really will or won't benefit you. Basically, they work by moving the opposite way the camera moves to cancel out that movement. This is true whether the stabilizer is built into the camera or the lens.
If you take a long exposure shot and slowly shake the camera in a tiny little circle, never exceeding the range of the image stabilizer, it should keep the image stable for the entire time, regardless of how many extra stops that is. On the other hand, if the camera is moving in one direction, you can easily exceed the range of the stabilizer.
When using an image stabilizer, there are some good practices to follow to make that it helps rather than hurts you. First, you may want to turn it off when using it on a tripod. I'm not sure about non-Canon stabilizers, but the older canon stabilizers (75-300, 28-135, and 100-400) can actually cause vibration on a tripod. You shouldn't need a stabilizer on a tripod, so it doesn't hurt to turn it off. The newer Canon stabilizer don't actually work on a tripod either, they are just smart enough to know that when there is nothing to stabilizer that they shouldn't do anything all and shut themselves down.
Stand still while using the stabilizer. If you are moving the camera, the stabilizer is trying to fight that motion. When it gets to the end of it's movement range, it gives up and resets. Taking a picture while it is resetting can be worse than taking a picture without a stabilizer. You need to hold the camera still for a moment (about 1/2 second) to let the stabilizer catch up. If you have in-lens stabilization, you can tell by watching the image in the viewfinder to see when it appears stable. I'm not sure how you know with in-body stabilization because the effects aren't seen in the viewfinder. My general rule of thumb is to turn the stabilizer off or switch to panning mode (see below) when I'm going to be shooting on the move.
Some stabilizers deal with the "motion" problem by having a "panning" mode (Mode 2 on Canon stabilizers). In this mode, when they detect continuous motion along the horizontal or vertical axis, they shut down that part of the stabilizer. This way, if you are panning from left to right, it will still stabilize the image up and down but won't effect left/right motion. If you are panning diagonally, it can't stabilize at all because there is too much up/down and left/right movement. Because it is smarter about shutting down the stabilizer when there is a lot of motion and turning it on again when their isn't, I find this mode useful for non-panning hand held shooting when I'm rapidly changing subjects.
Another good stabilizer technique is to brace the camera. If you can hold the camera against a wall, a table, or something solid, you can keep the movement range of the camera inside the allowable movement range of the stabilizer for a longer period of time. It's still not as good as a tripod, but it's an improvement over using a stabilizer hand held.
As I stated above, tripods and stabilizers only help with camera motion and not with subject motion. Raising your ISO works with both. It makes your camera more sensitive to light, so you can use faster shutter speeds. Every time you double your ISO, you can cut your shutter speed in half. So a shot that would require a shutter speed of 1/15s at ISO 100 will work with a shutter speed of 1/60s at ISO 400 or 1/250s at ISO 1600. That may be the difference between a reasonably frozen subject and a blurry one.
You may be wondering how 1/60s got to 1/250s when anyone with any math skills knows that if you cut 1/60 in half twice, you get 1/240. Well, it appears that early photographers weren't numbers people. They started with 1 second, split that into 1/2, then 1/4, then 1/8. Then they got worried that they were going to have ugly looking numbers like 1/16, 1/32, and 1/64. They figured no one would mind if they made them just a skitch longer and used 1/15, 1/30, and 1/60 instead. The problem was, this would lead to 1/120, 1/240, and 1/480, so they made them just a tad faster and used 1/125, 1/250, and 1/500. It's close enough and it makes the artsy folks that don't like numbers a little happier at the expense of confusing people that know their numbers.
You may be objecting to raising your ISO as a means to getting a faster shutter speed. Higher ISO pictures have more noise, lower dynamic range, and other image quality shortcomings. Life is full of trade-offs. A noisy picture is not as appealing as a noise free picture, but it's a darn sight better than a blurry one. Getting your shutter speed fast enough is paramount. You have to do what it takes. You can do some things to clean up noise later. You can't recover from blurry.
So if your problem is holding the camera still, use a tripod if you can and and image stabilizer or high ISO if you can't. If your problem is freezing your subject, forget about the tripod and stabilizer and bump up your ISO. While the marketing types might have you convinced that an image stabilizer is what you need to cure your blurs, you can see that the ability to take good pictures at high ISO is often better because it works for both camera motion and subject motion.
I have one more trick for getting non-blurry pictures. Sometimes your subject and camera motion are just too much even at your highest ISO and widest aperture. In those cases, you have to cheat a little. You can set your camera to it's highest ISO and aperture and then tell the camera to underexpose the image by a stop or two. You can do that yourself when shooting in manual mode or you can dial in exposure compensation and use aperture priority, shutter priority, or program. That will get you a faster shutter speed but will result in a darker picture. You correct this by increasing the exposure when you process the picture. This trick works much better in RAW than JPG. It will result in a sharper picture, but the noise levels will be nasty. Be prepared to do a lot of noise reduction and loose a lot of fine detail.
How useful is this trick? Well, many cameras have some form of extended ISO. With my camera, I can go to ISO H, which is equivalent to ISO 3200. Internally, the camera is doing the exact thing that I described - shooting at ISO 1600 and then boosting the exposure by 1 stop. Personally, I think I am better off shooting at ISO 1600 and adjusting the exposure myself later because I more control.
So to summarize - if your shutter speed is too low, you'll get a blurry picture. A tripod helps prevent camera motion but doesn't help with subject motion. A stabilizer works like a tripod, but not as well. Don't move when shooting with a stabilizer. Boosting your ISO will get you faster shutter speeds, which helps with both camera motion and subject motion.
Any questions? Corrections? Elaborations on how other brands handle these issues?
One of the major enemies to getting sharp pictures is motion. If anything moves while the picture is being taken, the result is blur. The motion can come from the camera or the subject. It can be because the camera is on something moving (like a Disney ride), because the photographer is not holding the camera perfectly still, or because the all or part of the subject is moving.
One way to counter motion in photographs is to take the picture faster. If you take a picture at a shutter speed of 1/8000 of a second, that means that you will only capture the motion that occurs during that 1/8000 time duration (sort of). With a shutter speed that fast, it rarely matters if the photographer, the camera, or the subject is moving because it won't move very far during that time.
At the opposite extreme, if you take a picture with a shutter speed of 30 minutes, there is a very good chance that even "non-moving" subjects are going to have motion blur. The stars and moon, while apparently motionless, will visibly move across part of the sky during this time. The branches and leaves on trees will sway. All but the most still water will ripple.
Another issue, in addition to time, is magnification. The more you magnify (or zoom in), the more you magnify any motion. This "magnification" can take many forms - zooming in, walking closer, or using a smaller sensor. In the end, all that matters is the amount of the motion across your pixels. Ideally, if you want to freeze something, it should start and stop the picture on the same pixel. The more pixels that it moves across during the exposure, the more motion blur you'll see in your image.
There are several guidelines that have been developed over the years to help us pick a reasonable shutter speed. The most commonly heard is the inverse focal length rule. That's a complicated sounding name that basically means that your shutter speed should be equivalent to how zoomed in you are. For example, if you are using a 30mm lens, you should try to have a 1/30 second shutter speed. If you are using a 300mm lens, you are magnifying things more and should use a 1/300 second shutter speed.
The inverse focal length rule was developed back in the 35mm film days. For equivalent results, you should factor in your sensor size. Just as your 100mm lens on your camera might have the same field of view of a 150mm lens on a film camera, you should aim for a 1/150s shutter speed instead of a 1/100 second shutter speed. The reason is that it isn't the focal length that is important in determining how quick you need to be - it's the overall magnification of the system.
The inverse focal length rule is designed to compensate for a typical photographer hand-holding a typical lens and wanting typical results. It doesn't deal with subject motion. It doesn't guarantee perfectly sharp results. It doesn't apply to unusually steady or shaky people. It's just a general guideline.
I've never really seen a good rule for determine how fast a shutter speed is required when your subject is moving. It depends on a lot of different things - how fast the subject is moving, how close the subject is, how magnified the subject is, and what direction (relative to the camera) the subject is moving. The important thing to consider is how much the subject is moving around in the picture. If it is coming towards or away from you, it won't move across as many pixels if it is moving from side to side. If it is close or highly magnified, a little motion will produce a large effect. As a very, very, very general rule, 1/250s is usually good enough to freeze something moving towards or away from you and 1/2000s is usually good enough to freeze something moving from one side of the picture towards another.
So what happens if you can't get a shutter speed fast enough? You could open the aperture wider. That's why people pay so much money for "fast" lenses. They can open really wide so that you can get a faster shutter speed. That also makes your depth-of-field shallower, which might not be desired. Also, lenses tend not to perform as well when they are opened as wide as they can be.
You can add more light. That works great in the studio when you control the lighting, but not as well outside. Still, if the scene is dark, adding flash can be the difference between a blurring shot and an acceptable shot. Adding light with a flash is great for stopping motion because the light from the flash is usually present for a very short period of time (often less than 1/1000 of a second).
Assuming that you don't want to or cannot open your lens wider or add more light, you've still got a few options left - a tripod, image stabilization, and increasing ISO. A tripod is the ideal answer when the problem is camera movement. A good tripod can virtually eliminate camera movement. To get the best results from a tripod, you want to trigger the shutter without touching the tripod. You can do that with a wired or wireless remote or with the timer mode on your camera.
With shutter speeds between about 1/60s and 2 seconds, it can also help if you lock up your camera's mirror. When you look through the viewfinder or an SLR, you are seeing light that has gone through the lens and is reflected up to the viewfinder by a mirror. When you take a picture, the mirror swings up and out of the way so that the light can get to the sensor. The motion of the mirror causes a little vibration within the camera that can blur your pictures. Locking up your mirror before the shot prevents that problem. You don't need to do it for faster pictures because there isn't time for the vibration to cause a problem. You don't need to do it for longer pictures because the vibration dies down so quickly that it doesn't have a noticeable impact on the picture.
Using a tripod only helps stabilize your camera. It doesn't do anything to help with subject motion (unless your subject stops to look at your tripod).
An image stabilizer is sort of like a tripod in that it helps stabilize your camera. It's much more convenient to use, but it isn't nearly as effective. A camera on a decent tripod will always outperform a handheld camera using an image stabilizer. The stabilizer is for use when you can't or won't use a tripod. Like a tripod, it only helps deal with camera motion and not subject motion.
Stabilizers are often rated in how many "stops" they are good for. One stop is essentially a doubling of the shutter speed. So if you are using a lens that you get good shots with hand held at 1/60s, a stabilizer that gave your two extra stops would allow you to use the lens at 1/15s. The first extra stop doubles the time from 1/60s to 1/30s (remember, we're using fractions of a second, so longer times mean smaller numbers on the bottom) and the second extra stop doubles the time from 1/30s to 1/15s.
Stabilizers don't really give you "x" number of extra stops. We rate them that way because it's kind of close and it's easy. It helps to understand how stabilizers work so that you can see how they really will or won't benefit you. Basically, they work by moving the opposite way the camera moves to cancel out that movement. This is true whether the stabilizer is built into the camera or the lens.
If you take a long exposure shot and slowly shake the camera in a tiny little circle, never exceeding the range of the image stabilizer, it should keep the image stable for the entire time, regardless of how many extra stops that is. On the other hand, if the camera is moving in one direction, you can easily exceed the range of the stabilizer.
When using an image stabilizer, there are some good practices to follow to make that it helps rather than hurts you. First, you may want to turn it off when using it on a tripod. I'm not sure about non-Canon stabilizers, but the older canon stabilizers (75-300, 28-135, and 100-400) can actually cause vibration on a tripod. You shouldn't need a stabilizer on a tripod, so it doesn't hurt to turn it off. The newer Canon stabilizer don't actually work on a tripod either, they are just smart enough to know that when there is nothing to stabilizer that they shouldn't do anything all and shut themselves down.
Stand still while using the stabilizer. If you are moving the camera, the stabilizer is trying to fight that motion. When it gets to the end of it's movement range, it gives up and resets. Taking a picture while it is resetting can be worse than taking a picture without a stabilizer. You need to hold the camera still for a moment (about 1/2 second) to let the stabilizer catch up. If you have in-lens stabilization, you can tell by watching the image in the viewfinder to see when it appears stable. I'm not sure how you know with in-body stabilization because the effects aren't seen in the viewfinder. My general rule of thumb is to turn the stabilizer off or switch to panning mode (see below) when I'm going to be shooting on the move.
Some stabilizers deal with the "motion" problem by having a "panning" mode (Mode 2 on Canon stabilizers). In this mode, when they detect continuous motion along the horizontal or vertical axis, they shut down that part of the stabilizer. This way, if you are panning from left to right, it will still stabilize the image up and down but won't effect left/right motion. If you are panning diagonally, it can't stabilize at all because there is too much up/down and left/right movement. Because it is smarter about shutting down the stabilizer when there is a lot of motion and turning it on again when their isn't, I find this mode useful for non-panning hand held shooting when I'm rapidly changing subjects.
Another good stabilizer technique is to brace the camera. If you can hold the camera against a wall, a table, or something solid, you can keep the movement range of the camera inside the allowable movement range of the stabilizer for a longer period of time. It's still not as good as a tripod, but it's an improvement over using a stabilizer hand held.
As I stated above, tripods and stabilizers only help with camera motion and not with subject motion. Raising your ISO works with both. It makes your camera more sensitive to light, so you can use faster shutter speeds. Every time you double your ISO, you can cut your shutter speed in half. So a shot that would require a shutter speed of 1/15s at ISO 100 will work with a shutter speed of 1/60s at ISO 400 or 1/250s at ISO 1600. That may be the difference between a reasonably frozen subject and a blurry one.
You may be wondering how 1/60s got to 1/250s when anyone with any math skills knows that if you cut 1/60 in half twice, you get 1/240. Well, it appears that early photographers weren't numbers people. They started with 1 second, split that into 1/2, then 1/4, then 1/8. Then they got worried that they were going to have ugly looking numbers like 1/16, 1/32, and 1/64. They figured no one would mind if they made them just a skitch longer and used 1/15, 1/30, and 1/60 instead. The problem was, this would lead to 1/120, 1/240, and 1/480, so they made them just a tad faster and used 1/125, 1/250, and 1/500. It's close enough and it makes the artsy folks that don't like numbers a little happier at the expense of confusing people that know their numbers.
You may be objecting to raising your ISO as a means to getting a faster shutter speed. Higher ISO pictures have more noise, lower dynamic range, and other image quality shortcomings. Life is full of trade-offs. A noisy picture is not as appealing as a noise free picture, but it's a darn sight better than a blurry one. Getting your shutter speed fast enough is paramount. You have to do what it takes. You can do some things to clean up noise later. You can't recover from blurry.
So if your problem is holding the camera still, use a tripod if you can and and image stabilizer or high ISO if you can't. If your problem is freezing your subject, forget about the tripod and stabilizer and bump up your ISO. While the marketing types might have you convinced that an image stabilizer is what you need to cure your blurs, you can see that the ability to take good pictures at high ISO is often better because it works for both camera motion and subject motion.
I have one more trick for getting non-blurry pictures. Sometimes your subject and camera motion are just too much even at your highest ISO and widest aperture. In those cases, you have to cheat a little. You can set your camera to it's highest ISO and aperture and then tell the camera to underexpose the image by a stop or two. You can do that yourself when shooting in manual mode or you can dial in exposure compensation and use aperture priority, shutter priority, or program. That will get you a faster shutter speed but will result in a darker picture. You correct this by increasing the exposure when you process the picture. This trick works much better in RAW than JPG. It will result in a sharper picture, but the noise levels will be nasty. Be prepared to do a lot of noise reduction and loose a lot of fine detail.
How useful is this trick? Well, many cameras have some form of extended ISO. With my camera, I can go to ISO H, which is equivalent to ISO 3200. Internally, the camera is doing the exact thing that I described - shooting at ISO 1600 and then boosting the exposure by 1 stop. Personally, I think I am better off shooting at ISO 1600 and adjusting the exposure myself later because I more control.
So to summarize - if your shutter speed is too low, you'll get a blurry picture. A tripod helps prevent camera motion but doesn't help with subject motion. A stabilizer works like a tripod, but not as well. Don't move when shooting with a stabilizer. Boosting your ISO will get you faster shutter speeds, which helps with both camera motion and subject motion.
Any questions? Corrections? Elaborations on how other brands handle these issues?
