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Wednesday, September 1, 2010

Common Camera Terms

Controlling The Camcorder Picture


What is "auto mode" on a camcorder?

Your camcorder, I'm sure, has some sort of auto record mode. That means that it's going to set its own f-stops, its own shutter speeds, really set your white balance and your exposure, and the pros of that are obvious. It makes it so much easier for you to deal with. All you have to do is aim, press the record button and let the camcorder do everything else. However, the camcorder is not you. It can't think for you. It makes decisions based on information it gets like how bright it is or what the focus is, but creatively, that doesn't allow for a lot of room for you in there. So, if your camera has auto mode and you want to use it in auto mode, you can get by with it more than you think. If you've got a creative idea, however, you've got to switch to manual. You've got to make those settings yourself. The downside to auto mode is that auto modes don't really anticipate or know really what you want to do creatively with the image. It may change the exposure when you don't want the exposure to change. It may shift the focus to something that you don't want to be focused on. It does things in automatic mode. It does things that are intuitive to the electronics of the camera but maybe not intuitive to you: the camera operator or the film maker; the person responsible for telling the story. So, that's why camcorders offer manual. You have much more control in a manual environment. That said, auto mode does a pretty good job most of the time.

What does "exposure of the video" mean?

A lot of terms get thrown out there like exposure or shutter speed. Really that's all about exposure. Exposure is how much light is getting to the image center. Is it coming through an aperture? Is it on a shutter speed? It's really just about how much light reaches the chip and what happens to that light before it gets there. Exposure is not that hard to understand. If it's a hot exposure, it's bright. If it's a dark exposure, it's dark. You just have to make allowances for the correct exposure.

What is the "iris" of a camcorder?

A traditional iris is really just an opening, how much light is getting from the image sensor by what's called the iris, which is just the opening in between the glass and the image sensor. Now, that opening is measured in f-stops. The larger the opening, the smaller the f-stop. There are graduations in there as to what the f-stop is. You might see something like 5.6 or 11 or 16. That's really telling you how big the opening (iris) is. Now, that's important, because you obviously need a proper exposure. You need the right amount of light getting onto the chip itself. But some camcorders don't have an iris. They do what's called "electronically". They really just vary the gain or the brightness on the chip to do what an iris would do. It doesn't work exactly right, but it's how it's done in the smaller cameras. It's kind of like a television set that has a brightness control. You can turn it up, you can turn it down. It will make your picture brighter, or it will make it darker. But really, that's done electronically. So, the higher-end cameras, have the true iris in there, something that creates that opening, that f-stop, and then the less expensive cameras, although they do a great job, typically do it by varying the gain or the brightness level of the chip.

What is "video gain", and what does it do on my camcorder?

One of the features you might find on your camcorder is called gain. What gain does is amplify the signal of the image sensor, whether it's a CMOS or a CCD type of image sensor. It turns the brightness level up or down. It allows you to get a brighter image, but not having to deal with an f-stop or a shutter speed to do it. It allows you to brighten up that image, but there's a bit of a compromise to gain. The more you increase the gain, the noisier the image gets, or the film, or the grainier it gets. It's just amplifying the image off the signal... the signal off of the chip itself. So it works, but you have to use it cautiously. Too much gain, you can make a very noisy image. You can get a very grainy image. Too little gain, you get good dark blacks, but maybe your color saturation can fluctuate a little bit. So use gain, but remember it's affecting your image, it's affecting your brightness, without affecting a change in f-stop or shutter speed.



What is "shutter speed", and what does it do on my camcorder?

Well, shutter speed is kind of a term that's held over from the old film days because video cameras don't really have a traditional shutter on them. There's no actual piece of mechanical anything that opens and closes to let light through. It's really just done by sampling information off the chip. How often do we pull that information of the chip is equivalent to a shutter speed. So maybe what you've selected is 1/60 of a second, which is a fairly standard shutter speed, which means every 60th of a second, all the information that's on that chip is pulled off and put down to your tape. But you have other selections. You might have 1/3 of a second shutter speed, or all the way up to 2000, 3000, 4000. Think of it this way, the higher the shutter speed, the more detail you're going to get, because you're opening and closing, or pulling that information off more often. The more often you pull it off, the more detail you get. But, if the shutter is open more, it's also closed more, so that doesn't allow for as much light to come through. A slower shutter speed is going to allow more light to come through and give you better low light properties, but not as much detail. One of the things you have to consider, is that if you go below 1/60th of a second on a shutter speed, these cameras will tend to give you what's called a “lag.” This would be an image trailing behind, almost like a ghost image. So below a 60th, maybe to a 30th, you're OK, slower than that you're going to get kind of an effect that you may not want. When you move it up, you'll get more detail, but that also might be an effect you don't want. Let me give you a quick example: let's say you were shooting a helicopter, at 1/60th of a second, you won't see those blades, but neither would I if I was just looking at the helicopter. Move it up to 2000 or 4000 or even 10000, and those blades not only become visible, they look like their standing still, which is kind of going to fool the eye into thinking ‘why is that helicopter up there?' So shutter speeds, you want to use them for different things, but you also need to know when's it’s appropriate and when it isn't.

What does an "ND filter" do on my camcorder?

One of the options you'll have on your camcorder is to either purchase a neutral density filter that screws on in front of the lens or use a neutral density filters that may or may not be built in. Neutral density filters, or "ND filters", cut the amount of light that's passing through the lens to the chip. So, if you find yourself in some very bright situations, and you can't get the settings that you want, added image density might give you a little bit more flexibility in how your exposure is created.

What is "white balance" and how does it affect my camcorder's picture?

White balance is something you need to use on a regular basis because your lighting temperatures change depending on the environment you're in. And by temperature, I mean the color of the light. Shooting indoors under a florescent tends to give you one type of color but outdoors you get a different type of color. You need consistent accurate color and that's done by setting a manual white balance. What you're telling the camera is what white is, that's why we call it white balance. The camera will already know, based on the design of the camera, what black is, which will give you the entire color spectrum. So, you set up your white balance by getting into the environment that you're going to shoot in, set up something white, look for anything from a white card to a white t-shirt, fill the frame as much as you can with white, lock that color temperature in by pressing the button on the camera and now the camera understands the entire color spectrum under the type of lighting that you're shooting in.
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  • Title : Common Camera Terms
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