GalaxyCat Loc: Boston, MA

I understand changing shutter speed and/or size of the hole, but what does changing the ISO do in the digital camera?

RichardTaylor Loc: Sydney, Australia

It may allow you to select the shutter speed or aperture you want (depending on the light level and your camera). Increasing the ISO also increases the noise levels.

Darkroom317 Loc: Mishawaka, IN

It is like changing film in terms of speed. It would be like going from 100ISO film to 400ISO film. I'm not sure of the actual theory or mechanics of how it works with digital. With film the silver halide crystal size is the main factor that determines its sensitivity to light.

GalaxyCat Loc: Boston, MA

Does it do something to the light meter then? What does changing the ISO do?

mwsilvers Loc: Central New Jersey

Raising ISO settings increases the sensitivity of your sensor to light allowing you to get a well exposed image with less light hitting the sensor. The down side is that the more you raise the ISO the more visible sensor noise is generated. Its part of the exposure triangle along with Aperture and Shutter Speed. Aperture (the hole you were talking about) controls how much light hits the sensor, and additionally, the depth of field of the resulting image. The shutter speed is set slow for motion blur, and fast for stop action, and everything in between based on a variety of factors. Depending on the aperture or shutter speed you plan on using, and the lighting conditions you are shooting in, you may have to raise the ISO value to get a good exposure.

SharpShooter Loc: NorCal

Cat, yes, it does something to the meter.
The ISO is the sensitivity of the sensor.
The computer in the camera controls the lightmeter to read correctly and accurately no mater WHAT you change in the camera, so you keep getting the correct exposure.
SS

jdubu Loc: San Jose, CA

The shutter speed sets the time light is allowed to reach the sensor. The aperture (size of hole) allows how much light is allowed through to the sensor and ISO dictates how sensitive to light the sensor is going to be.

The slower the shutter speed, the more time for light to accumulate on the sensor. The larger the aperture size, the more light is allowed through at any given time length. The higher the ISO, the more light is recorded to the sensor at any given time length. And the opposite is true for all three. Faster shutter speed, smaller aperture and lower ISO means less light to the sensor.

For any given perfect exposure, you can change any one of the above to more or less than that given exposure. But to maintain that perfect starting exposure, one of the other (or a combination of the other 2 above) must be changed in the opposite direction to equal or balance back to the perfect exposure.

For example, you can change one item by -I stop but must do a single or combination of the other two to equal +1. You can change two or all three of shutter, aperture or ISO! As long as the mathematical equation in the end equals back to zero, your starting perfect exposure. There are reasons as to what to change and why to change it and that is what makes you the photographer and the camera a tool. You may also decide not to have an equal equation to the perfect exposure and want to lighten or darken your exposure to realize your vision of that photo.

Learn the benefits and problems that settings of shutter, aperture and ISO provide and you'll find that the line between benefit and problem changes depending on what you want your photo to look like.

GalaxyCat Loc: Boston, MA

I went to www.nikonusa.com and I still didn't get the real technical answer to this question. How exactly does the camera change the "Sensitivity of the sensor?" Maybe it is proprietary information, but I will keep looking.

GalaxyCat Loc: Boston, MA

I don't think you can change the pixel size, light sensitivity of the pixels - hardware is hardware. Any comments?

rehess Loc: South Bend, Indiana, USA

It's like a volume control on a circuit attached to a microphone.

jdubu Loc: San Jose, CA

As I understand it, it's analogous to a dimmer switch with a light bulb, ISO dials in sensitivity to light to each photo sensor electronically. Do you really need to know the nuts and bolts of how each company formulates the ISO electronics? Suffice to say, knowing a lower ISO is less sensitive to light exposure and higher ISO means more sensitive light exposure (along with the noise ramifications at both ends) is what I need to know to go out and shoot.

boberic Loc: Quiet Corner, Connecticut. Ex long Islander

Think of the human eye. Pupil (opening size) is the aperature(f-stop) eye lids are the shutter (how long the eye is open) speed. The retina is the sensor(the sensitivity of the retina determines how much light is transmitted to the brain)

GalaxyCat Loc: Boston, MA

Okay. A dimmer switch on each pixel... that's a lot more hardware than one dimmer/volume-control of a light bulb/microphone. Or is it done in software?

GalaxyCat Loc: Boston, MA

Maybe somebody knows, someone in the industry can tell us. I want to know the guts.

rehess Loc: South Bend, Indiana, USA

How much electronics do you know?? Do you understand "the guts" of how an amplifier works, for example?