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What is "focus", and how does it work on my digital camera?

How Digital Cameras Work

Mark Comon (Vice President, Paul's Photo, Torrance, CA) gives expert video advice on: Why would I use the "image stabilizer" feature?; How do various image stabilizers differ?; What shutter speed range do I need for my digital camera? and more...

What is "focus", and how does it work on my digital camera?

On your digital camera the focus is the distance, or how far the subject is from the camera. The camera focuses by looking through a window in the camera, and it sees an out-of-focus image and an in-focus image, and electronically lines those up by twisting the lens to find the right distance. The focus works so that we get clear pictures at any distance. Whether it's near or far, the camera will adjust for that for you.

What is "autofocus" and why do I need it for my digital camera?

Auto-focus, all of our cameras today are auto-focus. So you need to have one that will focus on your subject. If your subjects are still, not moving, all cameras will do a great job. If you shoot pictures in low light, you need a more sensitive camera that will do a better job focusing in low light. If you're doing moving subjects like sports in action, you need to have a camera with what's called tracking auto-focus. That's generally found on the SLR type cameras, not on the pocket cameras.

Why would I use the "image stabilizer" feature?

Image stabilizer is a cool feature on today's digital cameras; and basically what it is is shake reduction. So if you can't hold the camera still enough to take a picture, the camera automatically adjusts for that for you, to hopefully give you a still picture. One thing I need to caution you on, though: you look at the ads on television and a lot of them don't portray image stabilizer properly. Remember, it's MY motion, the camera's motion, that it can stop, not the motion of the subject in the picture.

How do various image stabilizers differ?

There are three types of image stabilizing technology used in today's cameras. The first and the best is "optical" image stabilizer, where there's an actual motor in the lens that adjusts one of the lens elements. So if I'm taking the picture with the camera, and I tip the camera down slightly, one of the lenses will tip back to compensate for that. That's called the "optical" image stabilizer. That is what I would recommend you look for in your digital camera is the optical stabilizer. It's made by some of the top brands. Other people employ what's called a chip or "sensor shifting" technology, where the actual imaging chip will move up and down to compensate for your motion. That's okay, but I'm still not a believer in the moving of the imaging plane, because for years we've been told that's a sacred, hard, fast thing; where that image sensor needs to be rock solid with the camera. The "electronic" image stabilizes computer technology, kind of like sharpening in Photo Shop, where it looks at the image, and throws away the blurry pixels, and redefines the edge around it. It's okay, but you're much better off with the "optical" stabilization or the chip, or "sensor shifting" technology, than the "electronic" stabilizer.

What is an "aperture" and what does it do in my digital camera?

With digital cameras, an "aperture" in a camera can also be known as the "F-stop" or the lens opening. It's basically the size of the hole in the lens, so when you're looking through the lens, you look through the lens wide open, as you take the picture it closes down to adjust the amount of light coming through. Therefore the aperture, or F-stop, or lens opening controls the amount of light. The bigger the hole, the more light comes through. The smaller the hole, the less light comes through. The aperture also affects the amount or quantity of focus called "depth of field."

What is an "aperture range"?

The apeture range on your camera is how many f-stops or how much adjusting can you do on the apeture, or the f-stop or the lens opening. And that's generally, on your compact digital cameras, built into the camera. You only have a 3 or 4 f-stop range on the setting on the camera. On your SLR-type camera, you may have 1 or 12 f-stops available to you to set.

What aperture range do I need for my digital camera?

It all depends on what kind of pictures you're going to take. If you're shooting a lot of low-light pictures, you need a wide lens opening: f/1.4, f/2. or f/2.8 at the biggest. If you want to shoot a lot of landscape pictures where you want infinite focus, you want f/11,f/16 or f/22 in your range. So, that depends on the kind of camera you're going to buy. So, in looking for your apeture range, it's not how many ranges or how big a range, but does the range get to the point that you want for the pictures that you want to make.

What is a camera's "shutter"?

With digital cameras, the shutter of a camera controls the amount of time that light comes through the lens. The longer the shutter is open for, the more the light that comes through. The shorter or less amount of time the shutter is open, the less light comes through. The shutter also controls the action stopping ability. The faster or smaller the shutter speed, the more action you stop. The longer the shutter speed or the more light that comes in, the less action you can stop.

What is "shutter speed"?

With the camera set to a thousandth of a second, very little light comes through. It's open for a very short time. If we open that to a two hundred and fiftieth of a second, a shutter speed where we can hand hold the camera will stop a little bit of action. If you open up to a sixtieth of a second, where maybe the movie camera will be able to see this, at a sixtieth of a second we don't even have the ability to hold the camera still in our hands without image stabilization technology. We open the camera more, to a fifteenth of a second, you can see that shutter's open for quite a long time. And even down to a half of a second. Wow. That's a long time. There's no way you can hold the camera still for that amount of time.

What shutter speed range do I need for my digital camera?

With regards to shutter speeds for digital cameras, just about any digital camera today will have a shutter speed to stop the action. You need a shutter speed of 25th or so to stop the action. You need a 5 to 1th of a second to stop some moderately fast action, and that's all you need. Generally pocket digital cameras have 3 or 4 shutter speeds, and that's more than enough.

What is "shutter lag"?

When you're taking a picture on any camera, there's always a delay between when you push the button and the camera takes a picture. This is called shutter lag. On your compact digital camera this shutter lag or shutter delay can be quite long and frustrating, so you're not able to take pictures of moving subjects. Even the children at Christmas time you can't manage because you press the button, wait, wait, wait, and finally shoot the picture. What causes the shutter lag is the electronics in the camera doing all the things that need to be done before it can take the picture - like focussing for distance, setting the light, getting the picture ready to go and warming itself up. Better cameras have lower shutter lag. And if shutter lag or lack of shutter lag is important to you, the best way to get rid of shutter lag is to buy the SLR camera type because they have practically no shutter lag and can shoot virtually instantly.

What is an acceptable shutter lag time for a digital camera?

One that doesn't frost your bacon! That's the right shutter lag. All digital cameras have shutter lag. The SLRs have practically none, the pocket cameras can be excruciatingly slow. You need to look at that and test the camera in bright light, in low light, and with moving subjects, because lower light and moving subjects will cause longer shutter lag, and that's generally where you want to shoot instantly--birthday parties, sporting events. You want to push the button and have it go now. The best secret again: SLR cameras are going to do a better job than the pocket cameras.

What is a camera's "flash"?

The built-in electronic flash on your digital camera is a built-in light source, for using when taking pictures in low light, when there's not enough light to shoot without extra light. So you have the flash either pops up or activates, generally an automatic, the camera decides there's not enough light to take a normal picture, I'm going to add more light through the electronic flash. The built-in flash on your digital camera is great for birthday parties, out to dinner with friends, holiday time. You have to remember that the built-in flash on your digital camera is a very small flash, it's good to eight or ten feet, no farther. How far is eight or ten feet? That's two adult's laying down side by side, no longer than that. You can't shoot the Christmas pageant, you can't shoot at the football game with your built-in electronic flash. The built-in electronic flash also gives fantastic red-eye, so if you love the red-eye effect, using the built-in flash makes perfect red-eye pictures.

What options do I have for lighting my still pictures with an external flash?

The built-in flash on our compact digital camera, very small light source, gives great red eye. If you switch to the SLR type camera, once again we have a small light source, gives great red eye. Remember the small light source, good to shoot 8 to 10 feet, no farther. To get rid of the red eye, the best way to eliminate the red eye is to turn off the small flash and add a big flash to the camera. The big flash to the camera, what it does: number one, it moves the flash farther away from the lens, and number two, gives you a larger light source. This light source is 8-10 times bigger than the built-in flash, giving less red eye and better pictures. So the bottom line, to get less red eye, big flash. I know, moms, you don't want to hear that. You don't want to carry a big flash anymore. But to get the pictures you want, that's the professional quality secret.

What is a digital camera's "LCD"?

An LCD on your digital camera is the viewfinder. It's how you see the picture: on the compact cameras, before you take the picture; on the SLR type, after you take the picture. You have to remember that the LCDs are not created equal on all digital cameras. Some cameras are brighter, crisper, clearer than others, so you need to test that to see which one you can see the best in comparing. But remember, the LCD has zero effect on the picture quality. It just is how you view the picture.

What is "power draw" and how does it affect my digital camera?

Power draw on your digital camera relates to how long the battery life is. With today's digital camera technology, they've really got the technology, the cameras are good enough so that the power draw or power drain isn't an issue any more for most people. This is due to a combination of efficiency in the electronics of the camera and also the efficiency in the batteries. The batteries in digital cameras are so much better today than they were three years ago. Most digital cameras can get between one hundred and four hundred pictures on an average battery charge. So, to me, power draw is a non-issue today.

What power draw factors should I consider when buying a digital camera?

The power draw function of your digital camera relates to how many pictures you can take before you have to replace or recharge the battery. That's a combination of two factors. Number one the effeciency of the camera, how much power does it suck down. Number two, the type and the size of the of the batteries. You have to compare, it's kind of a hard thing to do, but you'll have to find rated life on batteries on your digital camera. But remember the rated life you find in the brochure or on the internet is just like the miles per gallon rating you see on your car. You never get 30 miles to the gallon like it says on the sticker of your car. Remember that for your digital camera. But, think about it, some cameras rate 75-150 pictures, others rate 200 - 400 pictures. So know that if you are buying a camera that has the 200 - 400 rating, you're generally going to get twice as many pictures per charge as you are with the one that going to give you 75 - 150 pictures. That's what you need to know. Once again, it generally relates to the size of the batteries and how many batteries there are. If you have a camera that takes two double A batteries versus a camera that takes four double A batteries, the four double A batteries' going to give you, generally, twice as many pictures. That camera is going to be quite a bit bigger and heavier, because it has four batteries versus two. That's what you need to know about power draw on your digital camera.