Photography Assignment 3/5, 3/6

The third ingredient for exposure is ISO. ISO is a measure of how sensitive your film (sensor) is to light. A higher ISO setting will result in a more sensitive sensor, and will therefore decrease the length of time (shutter speed) needed to take a picture. A low ISO setting will result in a less sensitive sensor, and will therefore increase the length of time (shutter speed) needed to take a picture.

It is generally considered best to shoot at the lowest ISO possible to capture the cleanest images possible. Shooting with a high ISO value results in increased grain size and noise.

Grain is another term that has come from film photography and it refers to the visible interruptions in smooth gradients. These interruptions look much like grains of sand...hence the name. For example:




Noise is the photographic equivilent to static in music. Noisy pixels are colorful pixels not part of the image recorded. Noise is a bad thing! We try to shoot at the lowest possible ISO possible in order to avoid noise, but sometimes in low light situations we have no other choice. The following picture is an example of a very noisy picture.





High grain pictures are often converted to black and white pictures, which is what we're going to do today!



Your assignment:

1. Set your camera to aperture priority and open the aperture as wide as it can go.
2. Set the ISO as high as possible (1600 on Nikon, 800 on Canon I think).
   
3. Take a picture of someone's face in the best light that you can find (hallway, outside, right by a window.
4. Set the ISO as low as possible and take an identical picture.
5. Convert each of the two images to black and white in Photoshop.
6. Label and post the two images to your blog.