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Image Stabilization vs. High ISO

Image Stabilization (also called Anti-Shake, Vibration Reduction) is a technology present in some digital cameras that moves either a lens element (optical image stabilization or O.I.S. or simply, IS) or the image sensor (CCD Shift) to compensate for camera shake. In doing so, it eliminates, or reduces the likelihood of obtaining, blurred images due to camera shake.

High ISO (also called Intelligent ISO, Anti-Blur, Picture Stabilization, Digital Image Stabilization, Electronic Vibration Reduction, etc.) is a scene mode that favours the use of a high ISO so as to permit the camera to use a shutter speed fast enough to eliminate, or reduce, the effect of camera shake and/or subject movement.

There is some controversy -- and a lot of confusion -- around the use of the term "IS" or "Image Stabilization." In this article we take a (calm and) detailed look at how IS and High ISO work, their advantages and disadvantages, and what consumers should really be looking for.

To fully understand why we need Image Stabilization or High ISO -- and their importance to photographers -- we first need to understand the two main reasons why we usually get blurred pictures.

REASON #1: CAMERA SHAKE

Whenever you press the Shutter-release button to take a picture, you move the camera, even if imperceptibly. You may not be aware of this slight movement and, depending on how steady your hands are, your images may suffer from some amount of blurriness.

If your hands are rock steady, plus you squeeze the Shutter-release button ever so gently, the blur may be so slight that it is visually unnoticeable in your images.

If, however, you do not have steady hands and/or you ram the Shutter-release button forcibly down every time you take a picture, chances are good the camera will "shake" when you press the Shutter-release button and you end up with blurry images.

The likelihood of this "camera shake" increases as the focal length used increases (e.g. when you zoom). As the focal length increases, the slight movements of the camera get magnified so that blurred images will more easily result.

REASON #2: SUBJECT MOVEMENT

The second reason why images come out blurred is simply because your subject moves during exposure (the subject moves while the shutter is open and the camera is still recording the scene).

If you look at the individual images of a movie of a moving subject, you will notice that almost all the images are in fact blurred! This is because the subject moved during exposure. However the frames of a movie are played back so fast (about 30 frames per second) that our eyes cannot necessarily register each single blurred image and so overall the movie looks sharp to us.

Long ago, a subject would be admonished to "sit still and do not move" for the duration of an exposure -- which could last a couple of seconds to minutes. Since the camera was on a tripod, there was little chance of camera shake. So the only risk was that the subject moved and a blurred image would result due to subject movement.

COUNTERING CAMERA SHAKE: FAST SHUTTER SPEED VIA HIGH ISO

Before the advent of Image Stabilization technology, the "cure" for camera shake was to:

1. Place the camera on a sturdy tripod (or some other level surface) and use a Shutter-release cable, a remote controller or the self-timer to trigger the shutter.

3. Use a fast enough shutter speed to eliminate the need for image stabilization. If the shutter speed used is not an important photographic consideration (i.e. you are not trying to freeze action using a fast shutter speed or depict action using a slow shutter speed), then using a fast enough shutter speed means that the effect of camera shake will not have time to register on the picture.

If you use a shutter speed that is faster than the movement of the camera, camera shake will not be a problem because the image will have been taken (shutter will have opened and closed, and the scene recorded) even before the camera movement can register.

Reciprocal of Focal Length Rule of Thumb

The rule of thumb here is that to be able to handhold a camera safely (i.e. without incurring camera shake), you would need to use a shutter speed that is the reciprocal of the [35mm equivalent] focal length of the lens used. This is not complicated to understand: For example, when you use a [35mm equivalent] focal length of 55mm, you would need a shutter speed of 1/55 sec. (or faster) to be able to safely ignore camera shake; when you zoom to a focal length of 100mm, you would need a shutter speed of 1/100 sec. or faster; further zooming to (or using) a focal length of 420mm, you would need a shutter speed of 1/420 sec. of faster.

Note that using a fast enough shutter speed is not the same as "image stabilization." In fact, there is no need to stabilize the image, and hence no need for image stabilization. Using a fast enough shutter speed eliminates the need for Image Stabilization.

If your camera meters the need for a slow shutter speed which will cause camera shake, there are two ways to switch to a faster shutter speed:

1. Open up the aperture. Opening up the aperture (makes the hole bigger and therefore) allows more light to come in and so reduces the time the shutter needs to stay open. ["Shutter speed" is simply the time the camera keeps the shutter open.]

2. Often, especially in low-light situations, this will not even give you a fast enough shutter speed to hand hold the camera, so the second way is to use a higher ISO.

At a fixed aperture (let's say the aperture is already opened to its max.), a higher ISO allows the camera to use a faster shutter speed. If that shutter speed is fast enough for safe hand holding the camera (using our reciprocal of focal length rule of thumb mentioned above), then there is no need for image stabilization. This is the premise upon which High ISO, Intelligent ISO, Picture Stabilization, Anti-Blur, Digital Image Stabilization and Electronic Vibration Reduction (to list only the most common High ISO terms) rely on to do away with the need for equiping the camera with an image stabilization technology.

So, before the advent of IS, photographers were already manually upping the ISO so that they could use a fast enough shutter speed that will counter camera shake. The High ISO scene mode simply automates this process, i.e. by selecting this scene mode, you are telling the camera to go ahead and select a high ISO.

High ISO vs. Auto ISO

High ISO scene mode favours a high ISO.

Contrast this scene mode to Auto ISO which always favour a low ISO.

Typically a camera will restrict the ISO values it will use in Auto ISO to those that will give an acceptable level of image quality. So, for example, even if your camera has ISO range from 100 to 1600, Auto ISO may be restricted to ISO 100 to 400 only. Favouring a low ISO means that the camera can deliver lower noise, retain more image details, and therefore better image quality.

High ISO, on the other hand, will typically start with the highest ISO (in our example, ISO 1600), and couldn't care less about the noise issue, leaving it to the in-camera noise reduction software (really, firmware) to reduce the noise.

Noise & Image Detail Loss

There is currently one problem with the High ISO scene mode: noise (*1).

The noise introduced at high ISOs is exhibited as ugly blotches of colours you see in your images. Now, you know where these come from!

Also, in trying to remove the noise, the noise reduction software in your camera also unfortunately removes fine details in your images. Now you know why some of your high ISO images also have this "watercolour effect."

So while photographers gain a benefit (reduction of camera shake, hence less blurry pictures), they also pay a heavy price to use High ISO: noisy images and loss of image details (*1).

However, if you only print 4x6 in. images, or display small size for the Web, then the noise present at high ISOs might not be too apparent at these small sizes, and you may get away with using it.

More advanced photographers typically use digital cameras with manual modes and rarely, if ever, use scene modes, preferring to set the exposure (shutter speed, aperture and ISO) themselves. And when they use a high ISO, they expect noise and typically post-process their images in a Noise Reduction software to remove the noise (to a certain extent, still subject to image detail loss).

High ISO is a scene mode. It is not Image Stabilization technology, and it is incorrect to use the term IS when referring to it. Marketers do that all the time, so it is incumbent upon us as informed consumers to be able to tell the difference between the two.

To summarize: High ISO is a welcomed and useful scene mode, especially for the point-and-shoot crowd who do not know -- or care to know -- how to manually select a fast shutter speed or manually select a high ISO; or, as is often the case, they use a digital camera where there is no manual mode to enable them to do so. The benefit is reduced camera shake; the price is noise (*1).

COUNTERING CAMERA SHAKE: IMAGE STABILIZATION

As we mentioned earlier, Image Stabilization is a technology that moves a lens element (Optical Image Stabilization, or O.I.S.) or the image sensor (CCD-shift IS) to compensate for slight movements of the camera.

So, say we are using a focal length of 60mm, the reciprocal of focal length rule of thumb says we should be using a shutter speed of 1/60 sec. to eliminate camera shake. But if there is not enough light, the camera might need to use a slower shutter speed, say 1/15 sec., for a correct exposure.

At this slow shutter speed and without using a tripod, we will obtain a blurred image if we hand hold the camera. But, with Image Stabilization, we are now able to hand hold the camera without worrying about camera shake (1/15 sec. is 2 stops slower than 1/60 sec.).

If the light level falls further and the camera now needs an even slower shutter speed, say of 1/4 sec. (that's 4 stops slower than 1/60 sec.: 1/60 sec., 1/30 sec., 1/15 sec., 1/8 sec., 1/4 sec.), Image Stabilization will not help us eliminate camera shake in this case. It will, however, reduce its effect.

Note that IS works irrespective of the ISO used. Whereas High ISO forces you to use a high ISO (with resulting high noise and image degradation issues *1), IS allows you to keep at a low ISO while still reducing camera shake (thus keeping maximum image quality). That is, it does not mess with your selected exposure settings (you keep the shutter speed, aperture and ISO you want to use).

So, as you can see, IS is a wonderful technology worth having in any digital camera. It can make a big difference in being able to hand hold a shot either in low-light or when using long focal length. You can gain up to 2 or 3 stops. You can, of course, combine the use of High ISO and IS.

Let's look at some practical considerations:

• If you take mostly landscape photos and your camera is almost always on a tripod, then image stabilization will not help you nor is it needed (in fact, most digital cameras require you to turn image stabilization OFF when placing the camera on a tripod).
• If you take pictures mostly outdoors in sunny situations, or in studios with controlled lighting, you will almost always be using a shutter speed appropriate for the focal length -- and so image stabilization is not needed.
• If you like to take pictures at long focal lengths (telephoto shots) and hand hold your camera, image stabilization is very useful to help reduce the likelihood of blurred images due to camera shake.
• If you like to take pictures indoors in low-light situations where the subject is not moving, image stabilization is useful.
• However, Image Stabilization will NOT negate the effect of subject movement. Since IS only counters the effect of camera shake, it does not counter blurriness caused by subject movement.

Either a digital camera is equipped with this IS technology or it is not. Anything else is a misuse of the term.

IS is a technology worth having in any digital camera, and worth the extra cost.

COUNTERING SUBJECT MOVEMENT

There are a number of ways to counter subject movement:

1. Use a shutter speed faster than the movement of the subject -- fast enough to "freeze the action."

This shutter speed would be dependent on the type of movement in question: for example, to freeze a runner in action, a shutter speed of 1/125 sec. might be adequate; to freeze a racing car in action, a shutter speed of 1/1500 sec. or faster might be required.

2. Another way to freeze a moving subject is to use flash. Nothing is faster than light and so using flash will always freeze the subject in action (as long as the subject is within the flash coverage). But flash is not allowed in all venues, nor is it always desirable because the result of using the on-camera flash is often images that do not look very pleasant.

COUNTERING SUBJECT MOVEMENT: FAST SHUTTER SPEED VIA HIGH ISO

Most photographers will first open up the aperture to use a faster shutter speed. If this still does not give a correct exposure, they will then use a higher ISO.

As we have seen, using a high ISO allows us to use a faster shutter speed. By boosting the ISO high enough, we may be able to use a shutter speed fast enough to freeze the action and thus eliminate blur caused by the movement of our subject.

So, say our subject is a toddler running excitedly around the room and we need a shutter speed of 1/125 sec. to freeze the action. But indoors, there may not be enough light and the camera needs a shutter speed of 1/30 sec. for a proper exposure.

This slow shutter speed is a double problem: not only is it too slow to freeze the action of our toddler, it may also be too slow for us to safely hand hold the camera (assuming we are using a focal length of 60mm and thus require a shutter speed of at least 1/60 sec. to eliminate camera shake).

If we can boost the ISO up by 2 stops (say we are currently using ISO 100, so ISO 200 would give us 1 stop exposure gain, and ISO 400 would give us a 2 stop exposure gain). At ISO 400, we can now use a shutter speed of 1/125 sec. (1/30 sec. to 1/60 sec. = 1 stop; 1/60 sec. to 1/125 sec. = another stop; total = 2 stops). Now not only will we be able to freeze the action, but we have also eliminated camera shake! All without the need for image stabilization!

Some photographers will read this and conclude that High ISO is better than IS. That is what many marketing messages surreptitiously try to get across. What they do not tell you is that using a high ISO introduces noise in your pictures.

Unless your digital camera has a low-noise-high-ISO characteristic (and to date only one camera manufacturer can truthfully boast to have achieved this *1), any use of a high ISO will result in either unwanted noise and/or unacceptable loss of image detail.

Advertisements and specs boasting about the availability of high ISOs in a digital camera without this low-noise-high-ISO characteristic are therefore to be read in its proper context.

The availability of a high ISO can mean the ability to get a shot where otherwise you might not be able to do so because of the low light level. The average photographers using a Point-and-Shoot digital camera may never print beyond 4x6 in. and noise (and loss of image detail) may not be as big an issue as it is for more advanced photographers.

DOES HIGH ISO REPLACE IMAGE STABILIZATION?

So, is High ISO better than Image Stabilization? It looks like it on paper, doesn't it?

If you boost the ISO and use a fast enough shutter speed, you can counter the effect of both subject movement and camera shake. Image Stabilization can counter only camera shake. So, maybe after all, we do not need IS.

If High ISO sounds too good to be true, that's because it is!

We mentioned 2 problems with using a high ISO and we'll repeat them here for emphasis (because the marketing ads won't), and add 2 more reasons why High ISO is not all the solution it promises to be:

1. Using a high ISO introduces noise in your photos. Noise shows itself as unwanted and ugly blotches of colour all over an image.

Compact consumer digital cameras use very small image sensors that are characteristically prone to lots of noise when using high ISOs.

[Most Digital SLRs use large image sensors which usually have a low-noise-high-ISO characteristic and therefore the use of high ISOs do not result in unacceptable level of noise.]

2. In-camera noise reduction is too often accomplished at the expense of detail: we remove noise by smoothening out the pixels and in doing so we also smooth out details. The result is a watercolour-effect image.

3. You may not want to use a high ISO and/or a fast shutter speed. Say, you are trying to depict motion (e.g., a waterfall) and require a slow shutter speed for that. In this case, you want the water of the waterfall to look blurred and cloudy (depicting motion), but want the rest of the scene to be tack sharp. High ISO wants to give you a fast enough shutter speed -- and it may be too fast to depict motion.

4. In very low light situations, you may be using the largest aperture, highest ISO and still end up with a shutter speed too slow for safe hand holding the camera. In this case, IS may well save the day.

Remember, High ISO is just a scene mode and, like all scene modes, can be manually set on [almost] any digital camera. In other words, it is -- and has always been -- available in digital cameras. Simply set a high ISO yourself manually. After all, there's not much more effort required to select "ISO 800" as opposed to selecting "High ISO" in the MENU, is there?

WHAT'S ALL THE FUSS ABOUT?

Some readers may wonder, "What is all the fuss about? As long as the use of IS or High ISO results in images that are not blurred, why worry about the correct use of the term IS? Why worry at all which is being used? After all, doesn't the average consumer only care about the final results, however they are achieved?"

For arguments' sake, we'll grant you 50% of that reasoning.

However, note that margarine is not called butter, though consumers use both interchangeably to "butter" their bread.

Bottled spring water is not the same as bottled distilled water, even though consumers ingest both without fully understanding the difference.

You could use a wrench to hammer nails in [guess who has shamefully done this only just recently?], but it is not sold as a hammer.

There are differences in these "similar use" products that are important enough that their respective industry requires that a distinction be made in their labelling.

Likewise, High ISO is not IS. High ISO is simply using a high ISO. This in turn may or may not result in the use of a shutter speed fast enough to eliminate the need for IS. But, in this writer's opinion, it is not IS, does not replace IS, and should not be marketed as IS.

HOW ABOUT HAVING BOTH?

Isn't the ideal digital camera then one that has both IS and High ISO capability?

Yes, but hold on a minute. We have been discussing the wrong issues so far. Because marketers lead you through this garden path, we have also followed it so as to clarify the issues.

But now, it's time we come to the crux of the real issue.

Remember, High ISO is simply a scene mode and all digital cameras offer high ISOs, so there is really no issue here. All digital cameras today offer a High ISO mode (though maybe called one of the other variations); not all digital cameras offer IS.

So, if all digital cameras offer High ISO scene mode, all we have to decide really is whether we want our digital camera to have IS or not. Right?

Yep.

Though, there's something else to consider: since IS handles only camera shake, we still need the possibility to use a high ISO (for a fast enough shutter speed to counter subject movement). But at high ISOs, noise is too high and image quality degrades, so depending on what kind of photographer you are, High ISO may be a useful or useless feature.

But wait, there is a digital camera that has a low-noise-high-ISO characteristic image sensor! Now High ISO suddenly becomes practically useful! With such a digital camera, you can up the ISO and take low-light pictures without suffering image degradation.

Alas, currently this digital camera (*1) is not equipped with IS.

So now we see the real issue: do we choose a digital camera with IS (but where the image quality degrades at high ISOs) or one with a low-noise-high-ISO characteristic (but no IS)?

LOW-NOISE HIGH-ISO

Adding IS to a digital camera is not a difficult matter. More and more digital cameras (even from obscure brands) now has this technology and it is only a matter of time before IS becomes widely available in all the major brand digital cameras.

More difficult is designing and building an image sensor with low-noise-high-ISO characteristic. This is the problem of using a high ISO; the question that consumers should be asking is: how is the image quality at high ISOs?

(*1) Currently in the compact consumer digital cameras, only Fujifilm digital cameras with their Super CCD HR image sensors have low noise at high ISOs, making them the undisputed king of low-light photography.

We can divide digital cameras as falling into one of 3 (IS/High ISO) categories currently:

1. Have High ISO with unacceptable high noise and image detail loss; no IS.
2. Have IS, plus High ISO with unacceptable high noise and image detail loss;
3. Have High ISO with very low noise; no IS.

Here are the categories summarized in a table, with a fourth one added and highlighted (the ideal):

Cameras in Category #1 are good for sunny shots (since the use of a high ISO is then not required and shutter speed will almost always be fast enough to eliminate camera shake).

Cameras in Category #2 have IS but don't try to use their High ISO feature too much because the resultant images are too noisy for many photographers. For small prints and Web display, they are more than adequate.

Cameras in Category #3 do not have IS but have low-noise-high-ISO image sensors that give you low noise at high ISO values. They are perfect for low-light photography.

What we want are digital cameras in Category #2 and #3 to combine their respective strengths and create a new Category #4: i.e., be equipped with IS and image sensors with low-noise-high-ISO characteristics (i.e. produce very low noise when high ISOs are used).

So, look out especially for new digital camera models in the 3rd category [Fujifilm] coming out with IS; and, more difficult to achieve, cameras in the 2nd category [Panasonic, Canon, Kodak, Nikon, all the rest] using a low-noise-high-ISO image sensor.

WHICH ONE TO BUY?

So the real question is not whether to choose between IS or High ISO. It is to choose between IS and Low-Noise High ISO. Most every digital camera now offers High ISO, but only one offers low noise high ISOs.

And, the answer will depend on your type of photography.

Image quality is most important to me so I favour a digital camera with low-noise-high-ISO characteristic (Category #3). I have a pretty steady hand, and I can always use a tripod or other level surface for image stabilization. At least, I can be confident that each image I get is low noise, highly detailed, and of the best quality.

If you only print 4x6 in. images, or display small size for the Web, then the noise present at high ISOs might not be too apparent at these small sizes. Cameras in Category #2 may be more appropriate for you in this case.

Hopefully, the whole argument will soon be moot because it is just a matter of time (isn't it always) before we see compact consumer digital cameras with both capabilities. This will go a long way in allowing us to take low noise, highly detailed, and high quality indoors low-light shots without the use of a tripod or flash.

SUMMARY

High ISO is a scene mode that allows the camera to select a fast enough shutter speed that:

• may eliminate, or reduce, the need for image stabilization to counter camera shake, and
• may be fast enough to freeze action and thus counter subject movement.

Most every digital camera today offers the High ISO scene mode, so the presence of High ISO in itself is not an advantage.

Furthermore, the use of high ISOs introduces noise and image detail loss that are usually unacceptable for advanced photographers but may be unimportant to the average Point-and-Shoot photographers. The only exception to this are the Fujifilm digital cameras that are equipped with the Super CCD HR image sensor that has low-noise high-ISO characteristics.

Image Stabilization technology may be optical or image sensor based, and counters the effect of camera shake only. IS does not mess with your exposure settings (again, this may be more important to advanced than P&S photographers).

The ideal digital camera is one that is equipped with both IS and a low-noise high-ISO image sensor.

Digital SLRs usually use a large image sensor with low-noise high-ISO characteristics. Some have an image sensor CCD-shift IS built into the body that gives them the advantage of having IS irrespective of the lens used; others require you purchase IS-equipped lenses.

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Related Links:

- What Is... Noise?
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