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ISO and shutter speed

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Please forgive my noobness as I'm new to photography. How does ISO effect shutter speed?
 
Using a higher ISO allows shorter (faster) shutter speeds. Lowering the ISO allows longer shutter speeds.
 
ISO specifies how much light your chip gets to reach maximal values. For film, this was fixed and depended upon the film. Digital fotochips can work on different levels of light, but less light means more noise. Modern cameras are getting more and more tolerant though and work very well even at high settings. The best quality is still at min ISO, though.

Shutter speed specifies how long the picture is taken. A picture that takes 1 second to take will show nothing but movement blurr if you're photographing a running athlete. A mountain on the other hand doesnt care if you only require 1/1000 sec to take the picture, or 30 seconds.

The third value is lens aperture. If the lens is wide open, a lot of light will be on the chip, but the area of sharpness will be small. This is actually desireable in many situations, such as portraits. If the lens is closed, less light will get through, but the area of sharpness will get much wider.

Depending upon what you want, and how much light you have to work with, different settings for these three values might be desireable. In some cases you might even want a gray filter to reduce the available light, so you can make movement visible.
 
By itself, ISO does not affect shutter speed at all.

ISO affects exposure. You can counter that affect with shutter speed, aperture, or the amount of light.
 
ISO specifies how much light your chip gets to reach maximal values.
Actually, the ISO setting determines how much the analog voltage a pixel developes during an exposure gets amplified. A pixel is a group of analog transistors and a detector that developes a voltage when it is hit by light particles. The more light particles that hit the detector, the greater the voltage developed. Active pixel sensor - Wikipedia, the free encyclopedia

The amount of light the analog image sensor 'sees' is determined by the scene being photographed, the lens aperture, and the shutter speed - only. Amplification, based on the ISO setting, of the stored pixel voltage happens after the exposure has been completed.

After the analog voltage signal is amplified, it is run through an Analog-to-Digital (A/D) converter and the voltage amplitude the pixel detected is then converted into a 12-bit or 14-bit digital 'word. The camera's image processing computer does not understand analog information.
 
Okay, my formulation was maybe not as clear as desireable. I should have probably written something like "ISO specifies how much light can hit the fotochip before it reaches maximum". Anyway, yes, thats what I wanted to say, even if not with that much detail.
 
Okay, my formulation was maybe not as clear as desireable. I should have probably written something like "ISO specifies how much light can hit the fotochip before it reaches maximum". Anyway, yes, thats what I wanted to say, even if not with that much detail.
What's wrong with "ISO is the sensitivity of the recording medium to light"? Anything other than that just seems wrong or incomplete to me...
 
My understanding is that ISO doesn't enter into the process until after the image is captured on the sensor. Changing the ISO doesn't do anything to the sensor.... it only affects how much amplification the digital signal must receive once the shutter is closed. Raising the ISO does not make the sensor any more sensitive to light.
 
Any definition of ISO that includes the words signal, digital, or amplification is no good, IMO. Film has ISO too. (I make an exception for sensor, since film is technically a sensor too.)
 
Any definition of ISO that includes the words signal, digital, or amplification is no good, IMO. Film has ISO too. (I make an exception for sensor, since film is technically a sensor too.)

So you're saying upping the ISO makes a digital sensor more sensitive to light?
 
Any definition of ISO that includes the words signal, digital, or amplification is no good, IMO. Film has ISO too. (I make an exception for sensor, since film is technically a sensor too.)

So you're saying upping the ISO makes a digital sensor more sensitive to light?
I don't know all the technical stuff behind it, but isn't that the end result?
 
I don't know all the technical stuff behind it, but isn't that the end result?

I've understood that using a higher ISO to simply mean the data from the sensor gets processed more, the end result being not only a proper exposure but noise to go along with it as a result of that processing. If raising the ISO makes the sensor more sensitive to light, then why would that process result in more noise?
 
I don't know all the technical stuff behind it, but isn't that the end result?

I've understood that using a higher ISO to simply mean the data from the sensor gets processed more, the end result being not only a proper exposure but noise to go along with it as a result of that processing. If raising the ISO makes the sensor more sensitive to light, then why would that process result in more noise?
Increasing the ISO has ALWAYS resulted in more "noise", even before there was a such thing as a DSLR.
 

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