Startup and Latency Times
The slower the camera, the more shots you will miss
It's the critical moment of the ballgame: bases loaded and two outs. Your son is at the plate. The pitch is thrown.
You pick up your digital camera that has been sitting in your lap to capture the photo of a lifetime. Unfortunately, your camera has shut itself off. In the 30 seconds that it takes to turn back on, the moment is long gone.
Welcome to the wonderful world of digital cameras. Film cameras never had a problem with startup time, because they didn't use a lot of power. You turn the camera on and it's ready to take a picture.
Digital cameras are different. They need to activate all of their internal circuits. You know how long it takes your computer to turn on when you first push the power button? It's kind of the same thing. Your camera has to "warm up" before it's ready to take that first photograph.
When you camera is turned on, it is eating up battery power. Most of that power is used for the LCD screen, but it is also used when you take a photo and the camera writes information to the memory card. Since digital cameras use up so much battery power, most have a built-in timer that shuts the camera off when you haven't been using it.
This is a great feature because it conserves power. It's a terrible feature because right when you're ready to take a shot, you find that your camera has to "warm up" all over again.
Startup in Seconds
Since enough people have missed enough photo opportunities, the camera manufacturers are beginning to reduce the amount of time it takes for a digital camera to turn on. In fact, many ads for digital cameras now include the startup time.
You may be thinking that startup time will never be a problem for you. Why pay more for a camera that starts up in 5 seconds vs. one that takes 10?
I can only speak from personal experience: in the long run, waiting for you camera to turn on can be very frustrating. If you like to take photos of your children, you know that special moments are rarely planned. You walk into the room and spontaneously decide to take a photo. Waiting for you camera to fire up is the last thing you want to do.
On the other hand, there is no need to be obsessive about it. At some point the difference between a 2 second startup and a 3 second startup are hard to tell apart. Don't spend a ton of extra money for the camera with the fastest startup time, but do pay attention to cameras that take a long time to get going.
Starting up the camera may not be the only time you have to wait. Many digital cameras will take time to process a photo and store it on the internal memory card. This is referred to as the camera's latency.
Wikipedia defines latency as: "a measure of amount of time between the start of an action and its completion." In the case of digital cameras, latency is the amount of time between the moment you press the shutter and when the camera is ready to take the next shot.
Latency is especially important in any feedback mechanism, where a human needs to know that their actions have caused an effect.
The Higher the Latency, the More You Miss
Let's give an example of latency. You're taking photos of a person running around a track. You take one photo as the person runs past you. The moment you press the shutter, the camera begins processing the image and writing it to the memory card. While the camera is performing this action, you can't take another shot.
Right while the camera is happily processing away, the runner trips and begins to fall. No amount of shutter mashing is going to make the camera work faster. The moment is over and the shot was missed.
You want the amount of time it takes the camera to process and save an image to be as little as possible. The lower the latency, the sooner the camera will be ready to take another photo.
Memory Cards and Latency
If you have compared memory cards at all, you will find that they operate at many different speeds. This is usually referred to as the read/write speed of the card, and is a measure in megabytes per second (MB/s) of how fast the card can process information.
For example, a SanDisk Ultra II CompactFlash card can write data at 9 MB/s and read at 10MB/s. A Lexar Pro Series CompactFlash can read and write at 12 MB/s.
A faster card has two advantages: it reduces the amount of time your camera takes to store a photo on the card, and it reduces the amount of time it takes to copy photos from your card to your computer later.
A fast card should reduce the latency of your camera. You should realize that the camera still has to process the image internally before it can save it. If the camera takes a long time to perform this processing, then the overall latency when you take a photo will be improved by a fast card, but not eliminated.