In photography, what does ISO mean and how it affects the clarity of a photo.?

Question

Could anyone please tell me what does ISO mean in photography and how does it affect the photo. Is it the speed of the aperture ??

Answer 1

The "speed of the aperture" is not an accurate term. A lens' aperture is simply the opening of the iris. It's primary characteristic is how wide the opening is. There is no speed associated with it. Although on any particular shot, there will be a certain "speed" (shutterspeed) related to how wide the aperture is, it is a term more directly related to the *shutter* than the aperture or ISO.

ISO, in the photographic sense, is a standard measure of light sensitivity for your imaging medium. There are actually TWO standards to speak of (and before ISO became *the* standard, there were *other* standards, like ASA...but let's not get sidetracked). Folks will always refer to "film speed," which is a reference to the ISO standard for light sensitivity in *film* imaging, which technically not the right definition to refer to anymore. Actually these days, most people refer to *digital imaging* ISO, which is similar, but different than film ISO. The term itself--ISO--It's really a shortened reference to the International Organization for Standardization's, which documents many standards, not just film speed and digital still camera exposure index standards.

ISO earned the name "film speed" because a film emulsion that is more sensitive to light would require less exposure time to capture an image (or alternatively, a smaller aperture). A film that took less time to expose a shot was considered a "faster" film, hence, a higher ISO rating. Faster films were useful to shorten the exposure time necessary to catch low-light shots. But a downside to those film stock was that the grain of the emulsion was rather noticable in development--literally, bigger fatter crystals vs. slower film emulsions. You would get grainy pictures. If you ever shot an old b&W 3200ISO film, you would remember how grainy the images were compared to the same image shot with an ISO100 film.

The digital photography equivalent ISO standard is actually an entirely separate set of ISO standards. But it serves the same purpose--a method for assigning and identifying ISO standard speed ratings, ISO standard output sensitivity values, and recommended exposure index values, for digital still cameras. The ISO rating says that a given photosensor array, must be able to produce a particular image quality for a manufacturer to be able to say that it takes images at that ISO rating (technically called a "digital still camera exposure index").

Unlike film, which is capable of working at only one ISO rating, photosensors are capable of operating at various ISO sensitivity ratings because their output signal can be electronically amplified. Is your sensor actually "becoming more sensitive to light?" No. You can't change a sensor's native sensitivity. You're simply turning up it's output signal. So, when you set a digital camera to take pictures at an ISO1600 setting instead of ISO100, you're telling it to amp up the weaker signal so that it will still produce an image of a particular light intensity given a specific amount of incoming light.

But here's the key for you...just like film speed ISO, photosensor ISO loses image quality when you force the photosensors to work at at higher sensitivities and with less light. The root cause isn't emulsion grain (as it is in film ISO's problems), but signal noise. Since you have less light to work with, the camera tries to "turn up the volume" to reach higher ISO sensativities, as if you were trying to hear a very quiet song over your radio. The "image signal" becomes more and more difficult to distinguish from the "static," or noise. You'll see mottled variations in the color of a blue sky, for example, when in real life, the sky is a smooth blue color. That's image noise, and it's significantly more noticable in higher ISO settings.

So, when taking pics, when should you put it in high ISO? The answer is debatable. But if photodocumenting what you see is your objective, the answer is as seldom as you possibly can. Keep the ISO as low as possible to avoid unnecessary noise. This, of course, is only an issue when you're trying for low-light shots without flash. You'll find that in brightly lit scenes, or when using a flash, you can always stick to ISO100 or ISO80 (some cameras go as low as ISO 50). But when the lights dim, and you have an artistic preference for not using flash, that's when you'll have to start pushing the ISO up. What happens is that the shutter speeds start to get so long that you can't keep the subject from blurring in the picture. That's when you know that you're going to have to push the ISO up. If your subject is inanimate (doesn't move), then you can avoid pushing ISO up by putting your camera on a tripod, and use those longer shutterspeeds to get more light in the camera. But if your subject is moving, then you'll have no alternative but 1) push ISO up, or 2) use a flash. If you use a flash, you'll change the artistic impression of the shot. If you push the ISO up, you'll concede image quality. Both are a mixed bag. One thing you could do if you had the option, is switch to a camera/lens that is capable of wider aperture settings, letting in more light. Lenses that can stop down to f2.0 or less are highly sought after for it's ability to catch images in low light without going up to a noisy ISO.

There is one camera company (currently) that is changing the relationship between noise and higher ISO. To get to the higher ISO indexes, instead of just turning up the volume on a regular sensor, Fuji has put the work into developing a more sensitive sensor. Somebody smart is working at that company. They've been blowing away competition with their Super CCD sensor, by getting lower noise in high ISO shots without the need of noise-reduction algorithms (which can reduce noise only by sacrificing image detail), and as far as sensor technology goes, theirs is the best sensor out there to date. Personally, I hope to see other manufacturers follow its lead.

One last note regarding noise, and photography with high-ISO. It can be argued that *some* noise is not only an acceptable part of imaging, but can lend character that can add to an image's artistic qualities rather than detract. Would old world-war II era photographs posess quite as much nostalgia if they didn't have that grainy texture? That sepia tone? That point is of course debatable ad nauseum, when imaging steps away from photodocumentation, and into photography as an art form.

Answer 2

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The ISO function sets the light sensitivity of the camera's image sensor (this is similar to the speed rating of film. The higher the ISO, the more sensitive the image sensor and therefore the possibility to take pictures in low-light situations. If you find the camera is using a shutter speed that is too slow (1/60 sec. and slower) to handhold the camera steady and shake-free then you might select the next higher ISO which will then allow you to select a faster shutter speed. F-stop is the measure of the aperture setting on a lens. The greater the number, the less light it allows in, which means the aperture gets smaller, making the depth-of-field more extensive. Hope this helped :)

Answer 3

What Does Iso Mean Camera

Answer 4

ISO:International Organization for Standardization. The "normal" range of ISO is about 200 to 1600. With today s digital cameras you can sometimes go as low as 50 or as high as 204,800. The number chosen has two important qualities associated with it. First, it sets the amount of light needed for a good exposure. The lower the number, the more light required. The more light that s required, the more likely a slow shutter speed will have to be used. That means low ISOs, like 100 or 200, are most often used in bright situations (like sunlight) or when the camera is mounted on a tripod. If you don t have a lot of light, or need a fast shutter speed, you would probably raise the ISO.

Answer 5

RE:
In photography, what does ISO mean and how it affects the clarity of a photo.?
Could anyone please tell me what does ISO mean in photography and how does it affect the photo. Is it the speed of the aperture ??

Answer 6

ISO sensitivity expresses the speed of photographic negative materials (formerly expressed as ASA).

Since digital cameras do not use film but use image sensors instead, the ISO equivalent is usually given.

What ISO denotes is how sensitive the image sensor is to the amount of light present. The higher the ISO, the more sensitive the image sensor and therefore the possibility to take pictures in low-light situations.

And, where you would have needed to physically change to a different roll of film if you wanted a different ISO speed, digital technology allows you to simply dial one in. In this way, you can record images taken at different ISO speeds on the same memory card.

Answer 7

International Standards Organization

If its really sunny out you want to be at ISO 100 or 200.

as the available light goes down and you start to adjust the shutter and aperture to compensate you will get to a point when your photos are starting to get to dark. That is when you will have to adjust the ISO up. At ISO 800 you can have shorter shutter speeds. If you are shooting indoors with no flash, more than likely you will have to shoot at a pretty high ISO like 1600 but you then run into the problem of your photos getting grainy. I like to think of ISO as how fast the film absorbs light. Always shoot at the lowest ISO you can. Unless of course you want grain.

Answer 8

The ISO number is not related to aperture size or shutter speed ...just represents how receptive your camera's sensor is to light.
Here are typical ISO numbers: 50, 100, 200, 400, 800, 1600.

As the number increases, your camera's sensor becomes more light-sensitive ...so in low light situation the large ISO number will be helpful to get a well expsed photo but with more noise(grains)...but it's still the most helpful way to make ur shots more lighty in low light conditions but it's not the only way ....u can decrease shutter speed and/or increase the aperture size....and the last thing is the flash((don't use it as ur 1 choice)).....good luck.

Answer 9

The ISO is how sensitive your cameras sensor is to light. The higher the number the more sensitive it is making it easier to shoot in low light conditions. Pretty straight forward but a very important thing to remember is the higher the number also means the more noise you are going to get in your photograph. So make sure to balance it out correctly.

For more information on ISO and related topics, I have written a detailed article which you can find on my website. http://samanthadonphotography.info/wp/?page_id=186. Feel free to check it out and if you have any questions I'd be happy to answer them for you :) I hope this has helped

Answer 10

ISO refers to the light sensitivity of the image sensor on a digital camera. Clarity is roughly same across the ISO range (except in relatively high portions of the ISO range, such as ISO 3200+). The primary function of the ISO control on your digital camera is to increase the amount of light being recorded by the image sensor, as to allow an increase in shutter speed (to maximize sharpness of image). The downside to increasing the ISO is the appearance of color noise in your photograph in low light situations.

Remember:
Higher ISO = Higher Shutter Speed
Higher ISO = More color noise in photograph

Answer 11

ISO is basically how sensitive you want your camera sensor to be to light. If you want it extremely sensitive and to let in more light, than you want to bump your iso up. However, depending on the quality of your camera, this can impact whether or not a photo will be grainy or not in low light situations where you need to bump up your ISO.

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