Photographic Examples of ISO
A higher ISO number leads to more grain in the photo
The following photographs show the same photo where the ISO number changes from 100 to 1600. The aperture is kept constant, but notice how the shutter speed increases as the ISO increases.
Photo One — ISO 100
This is what a photograph taken at ISO 100 looks like. There is plenty of detail in the image, and all of the lines are smooth.
The aperture is f11 (good depth of field) and shutter speed is 1/10 of a second.
At this shutter speed you need a tripod for a clear photograph.
Photo One — ISO 1600
Here's the same photograph at ISO 1600. At this size, they look pretty much the same don't they?
The aperture is f11 but the shutter speed has changed to 1/180 of a second!
At this shutter speed you do not need a tripod for a clear photograph.
Photo Three — ISO 100 Detail
I have zoomed in on one part of the previous photograph to clearly illustrate the concept of grain.
Notice that even though I have increased the size of the images, the lines are still clean and colors (especially the light one in the background) are smooth.
Photo Three — ISO 1600 Detail
Now you should be able to see the difference between ISO 100 and ISO 1600.
Notice how the lines are no longer smooth, and the color is not consistent?
This is grain in the image. You will notice grain much more if you print the image, but you will also be able to see grain looking at photos on your computer.