Digital still cameras

Introduction

This tutorial covers principles of digital photography in general, but refers to these Canon cameras as examples:
PowerShot G1, G5, Pro1, Rebel XT
If you have a different camera, you'll find that the same functionality is present on your camera, though buttons and menus may be in places other than those shown here. Consult your owners' manual.

About Digital Cameras

Digital still cameras store photographs as digital bits on a memory card or tiny hard drive, as opposed to the film used in traditional cameras.
Rather than developing and printing film, digital images can be downloaded easily to a computer. A photographer also can instantly review shots on an LCD (liquid crystal display) monitor built into the digital camera. The memory cards can hold a large number of images. After downloading the images to a computer, the flash cards can be erased for reuse.
The main drawbacks to digital still cameras are:

• A slight delay that occurs between clicking the camera's shutter button and the camera actually taking the picture. The better the camera, the shorter this delay will be. Professional digital cameras do not suffer from this lag time, and the problem is becoming less pronounced even with cheaper consumer/pro-sumer cameras.
• A battery is required for operation, so you'll need to periodically recharge it (this can be done by connecting the camera to an AC power adapter and charging the battery in the camera, or by purchasing a separate AC battery charger).
• Photos that are not quite as high quality as what you get with traditional single lens reflex (SRL) cameras, unless you purchase a very high-end (and expensive) digital camera. But even a mid-range digital camera produces photos that are suitable for the vast majority of purposes, including Web publishing.

SLR vs. Non-SLR

There are two basic kinds of digital cameras: Digital SLR (single lens reflex) and non-SLR. Digital SLRs are generally more expensive and more accurate than non-SLR cameras, and include more professional features.
SLR cameras -- whether film or digital -- use a system of mirrors to take the image coming through the lens and reflect it up into the eyepiece. Thus, what you see in the eyepiece is exactly what you get on the camera back, where the image is recorded. In contrast, the eyepiece on a non-SLR camera looks out through a separate hole at the top of the camera. As a result, what's seen through the viewfinder is slightly different from what comes through the lens. What you see is not exactly what you get.
While we sometimes think of the ability to preview a shot as a hallmark of digital cameras, there is an interesting side-effect of using an SLR camera in the digital world: The mirror that reflects light from the lens up to the viewfinder blocks the digital image sensor on the camera back until the image is shot. Therefore, digital SLR cameras generally do not let you frame and preview your shot on an LCD screen before shooting -- you must frame your shot in the viewfinder, as you would with a traditional SLR camera.
Here is an animation showing how SLR cameras work.
Here is an animation showing how non-SLR digital cameras work.
There are a few digital SLR cameras that have come up with clever workarounds for this problem, but most digital SLRs, including the Canon Rebel, do not allow for LCD preview.
In this tutorial, the Canon Rebel is a digital SLR with no LCD preview; all other cameras are non-SLR with LCD preview.