What is ISO in simple terms?

Question

i have the option of ISO on my digital and was wondering what it was all about. Let's say i wanted to take some night photos on a longer exposure, how is my iso going to effect the photo?

Answer 1

ISO is a measure of sensitivity to light. Basically, how long does my camera sensor (film) need to be exposed to the scene to absorb enough light for my photo to appear.

Generally, if you want a long exposure (slow shutter) you should use a low ISO number, maybe 200 or 400. For your night photography I would recommend trying 400 first and if the shutter speed still isn't slow enough for your needs, bump it down to 200. Depending on the type of camera you have, beware that any ISO setting above 200 may give you very grainy (lots of tiny coloured dots) photos so experimentation will be necessary.

A low ISO, eg 50, 80 or 100 means very insensitive to light, therefore it takes longer for the photo to be exposed.

A high ISO, eg 800 or 1600 means it's very sensitive to light, therefore it takes less time for the photo to be exposed.

Photos taken at low ISO are smoother and have less noise and dotting than photos taken at high ISO. That's just the camera gods' way of preventing us from using high ISOs - because then life would be too easy for us photogs.

If that explanation doesn't quite work, consider the analogy that taking a photo is like filling a bucket of water using a hose.

LIGHT is the WATER

APERTURE is the diameter of the HOSE
(big hose fill fast, little hole fill small)

SHUTTER is how long the HOSE is left OPEN
(more water the longer it's open)

Then ISO is the size of the BUCKET you're filling.
(low ISO big bucket, high ISO small bucket)

Now that should either make it all crystal clear, or totally confuse you. ;)

Either way, may I recommend Bryan Peterson's simply excellent book "Understanding Exposure" that explains the triumvirate of APERTURE, SHUTTER, ISO.

Answer 2

ISO speed is simply sensivity to light
when you need to chand ISO?
-in lowlight condition which there a moving object which you cant let shutter opens more to gain enoughligt and produce clear image(not blurry)
-when you zoom in more than 4X and the light is not enough or your camera is not equipped with optical image stablizer

-when you have not a tripod and your handshaking make your picture blurry

finally you should know that ISO higher than 200 in non D-SLR cameras will give you noisy picture : then you sholud take your photo at highest size and so some photoshoping on it or Image resize to hide noise,
if ou want to have long exposure (more than 5 sec) try the least ISO ,, 50 gives you better and clearer result, to mimic overexposure reduce exposure -1/3 atleast

Answer 3

ISO film - the film is more sensitive to light. Less light is needed to expose the film.

ISO digital - the light in the picture is amplified. A certain amount of detail is present depending on how good the sensor is. A low quality sensor has much less detail than a high quality sensor. When you brighten a picture with less detail captured, a certain amount of mistakes are made in the image. This shows up as "noise".

Most digital SLR cameras have high quality sensors and can use a high ISO setting (meaning you can use a faster shutter speed and/or smaller aperture size). Most non SLR cameras will not have a good result if you do that.

Answer 4

Low ISO numbers provide the best image quality. Low ISO = low sensitivity to light = long shutter time to get sufficient light for a proper exposure.
The higher the ISO, the shorter the required shutter time, but you sacrifice image quality.
For a long exposure, use the lowest possible ISO in combination with a tripod.

Answer 5

ISO images are mainly used as source files from which to create media. As an example, most distributions of Windows,Linux release ISO images of the installation media. You are right. ISO files could not be edited directly. You need a tool to help you edit it. WinISO is a comprehansive ISO editing software that can access or manipulate ISO image files. Not only edit, but convert, extract, make, create, burn, mount and make bootbale ISO files.

Answer 6

ISO option means setting aperture and shutter speed manually ---instead of automatic A number is assigned to photo film to show how sensitive it is to light. To obtain a number for a new film, the aperture is set to /f16. Then a number of exposures are taken at various shutter speeds. The shutter speed giving the best piciture is then the ASA of the film. If 1/160th sec gave the best exposure, then 160 would be the ASA number of that film.

Answer 7

ISO is International Organization for Standards.Its the amount of lighting that enters your camera lens.In poor lighting you could increase the ISO,but the clarity in the picture will be less.ISO 100 is pretty much standard for a good picture.Go for 200 or 400 if the lighting is very poor.

Answer 8

ISO is to do with the speed of the film

"faster" film (higher numbers) is more sensitive to light than others