ISO...
ASA...
What does it all mean? What is the difference between 100 and 1000? The ASA (American Standards Association) scale is an arbitrary rating of film speed.
This is not typically used anymore as the mass has merged into a worldwide use of the ISO standard.
Derived from the Greek "isos", meaning "equal", The International Organization for Standardization chose this short all-purpose name instead of using its acronym "IOS" so that whatever the country and language, the short form of the organization's name is always "ISO" (pronounced "eye-so" but typically pronounced as "EYE-S-OH").
To put it simply, the higher the ISO number the faster the speed of the sensor or film.
Film speed describes how fast, or sensitive, the sensor or film absorbs the light that falls upon it.
I will mainly focus on the digital side as the majority of today's photographers lean more heavily towards digital.
Most Semi-Pro and Pro digital cameras allow you to adjust the iso sensitivity.
The majority of low to mid-range digital cameras have an ISO range that goes from somewhere in the neighborhood of 50 or 100 up to around 400 to 800.
A lower ISO number requires more light to obtain a proper exposure on a given shot.
The majority of people would be inclined to turn the ISO setting all the way up to obtain the most light possible.
What is wrong with this? Although a higher ISO setting will absorb more light and capture a good exposure even in low light, there is a problem.
The higher you set the ISO, the more "noise" there will be, causing your pictures to come out grainy.
With Technology today there are ways to employ higher ISO setting without developing a fuzzy photo.
These days, many digital cameras utilize some form of noise reduction for their higher ISO settings.
Though at first glance reducing noise may seem like a good route to go, it also has its own downfall.
Reducing noise is often accomplished by utilizing small amount of blur.
Though you may be able to blur out the noise, you will blur out the fine detail you are trying to capture.
In general, you would typically want to use the lowest ISO setting as possible.
The key benefit to using a digital camera is the ability to find the perfect setting instantly.
A photographer is able to shoot a photo and see it instantaneously giving him the ability to make corrections and shoot again.
For a clean photo a photographer would want to use a lower ISO setting.
When using a lower ISO setting, light is not always readily available.
There are two distinct way to compensate for lighting issues when using a low ISO.
A photographer will change the shutter speed to allow the shutter to stay open for a longer period of time, allowing more light to pour onto the sensor.
If a photographer uses a longer shutter speed, generally the camera will be mounted on a tripod, a mono pod, or some other form of bracing.
One additional option to obtain proper lighting, is to utilize a flash.
A key to using a flash is to not bath the subject being photographed in direct light unless desired.
Play around with different flash settings to obtain the desired results.
When shooting with a digital camera, a good starting ground is to set you ISO to 400 and adjust from there.
Lower ISO equals less grain and more clarity.
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