Saturday, September 13, 2008

video camera information

It's unavoidable — if you're serious, you've got to know some jargon. Fortunately, it's not too complicated. This page contains a few essential terms to get you started.
Shot: All video is made up of shots. A shot is basically from when you press record to when you stop recording. Like the individual photos which make up an album, the shots get put together to make a video.
Framing & Composition: The frame is the picture you see in the viewfinder (or on a monitor). Composition refers to the layout of everything within a picture frame — what the subject is, where it is in the frame, which way it's facing/looking, the background, the foreground, lighting, etc.
When you "frame" a shot, you adjust the camera position and zoom lens until your shot has the desired composition.
There is a general set of rules in the video industry that describes how to frame different types of camera shots.

VWS (Very Wide Shot): Shows the subject's environment.
WS (Wide Shot): Shows the whole subject.
CU (Close Up): Shows a feature of the subject.
Transition: Shots are linked (edited) in a sequence to tell a larger story. The way in which any two shots are joined together is called the transition.
Usually this is a simple cut, in which one shot changes instantly to the next. More complex transitions include mixing, wipes and digital effects. A moving shot (e.g. pan) can also be thought of as a transition from one shot to a new one.
The transition is very important in camera work, and you need to think constantly about how every shot will fit in with the ones before and after it. The key is not so much how the transition is achieved technically, but how the composition of each shot fits together.
Here are few more important terms. They will be explained in greater detail later:
Side-to-side camera movement.

Up-and-down camera movement.

In-and-out camera movement (i.e. closer and more distant).

Iris (Exposure)
The opening which lets light into the camera. A wider iris means more light and a brighter picture.

White balance
Adjusting the colors until they look natural and consistent.

Analogous to the shutter in a still camera.

Sound which is recorded to go with the pictures.

Video Camera Focus
The ability to manually focus your camera is a critical skill at any level of video production. This page shows you the basics — at the end of the page you can choose to continue and learn more advanced focus techniques.
Note: Manual focus is so important that most professional cameras don't even have an auto-focus feature.

Some Focus Jargon
Soft: Out of focus
Sharp: In focus
Depth of Field: The range of distances from the lens at which an acceptably sharp focus can be obtained
Pull focus: Adjust the focus to a different point during a shot

How to Use the Manual Focus
First of all, locate the focus control. Professional cameras usually have a manual focus ring near the front of the lens housing. Consumer-level cameras usually have a small dial (Note: you may need to select "manual focus" from the menu).
1. Make sure the camera is set to manual focus.
2. Zoom in as tight as you can on the subject you wish to focus on.
3. Adjust the focus ring until the picture is sharp. Turn the ring clockwise for closer focus, anti-clockwise for more distant focus.
4. Zoom out to the required framing — the picture should stay nice and sharp.
5. If the picture loses focus when zoomed out, check the back focus,
and make sure the macro focus is not engaged.
If you need to adjust your focus on the fly (for example, you're in the middle of shooting the Prime Minister's speech when you realize her face is soft), it helps to know which way to turn the focus ring. If you go the wrong way and defocus more, even if you correct yourself quickly you've drawn attention to your camera work. Try comparing the background and foreground focus. If the background is sharper than the subject, then you need to pull focus to a closer point (and vice versa).
Note: You will usually find the sharpest focus occurs at about the middle iris position.
Difficult Focus Conditions
You'll notice that focusing is more difficult in certain conditions. Basically, the more light coming through the lens, the easier it is to focus (this is related to depth of field
). Obviously it will be more difficult to focus in very low light. If you're really struggling with low-light focus, and you can't add more lighting, try these things:
· Make sure your shutter is turned off.
· If your camera has a filter wheel, make sure you're using the correct low-light filter. Remove any add-on filters.
· If your camera has a digital gain function, try adding a little gain (note: this compromises picture quality).
· Stay zoomed as wide as possible. If your lens has a 2X extender, make sure it's on 1X.

Video Camera White Balance
White balance basically means color balance. It is a function which gives the camera a reference to "true white" — it tells the camera what the color white looks like, so the camera will record it correctly. Since white light is the sum of all other colors, the camera will then display all colors correctly.
Incorrect white balance shows up as pictures with orange or blue tints. Most consumer-level camcorders have an "auto-white balance" feature, and this is how most amateurs operate. The camera performs its own white balance without any input from the operator. In fact, very few home-video users are aware of its existence. Unfortunately, the auto-white balance is not particularly reliable and it is usually preferable to perform this function manually.

To confuse the issue, the term "automatic white balance" has two different interpretations. On consumer-level cameras, it means completely automatic. On professional-level cameras, it can mean the white balance operation as described below (which is actually quite manual). This is because in professional situations, a "manual white balance" can mean altering colors using specialized vision processing equipment.
"Auto-white" means the completely automatic function (no user input at all)."Manual-white" means the operation described below. "Color correction" means any other method of adjusting colors.

How to Perform a Manual White Balance
You should perform this procedure at the beginning of every shoot, and every time the lighting conditions change. It is especially important to re-white balance when moving between indoors and outdoors, and between rooms lit by different kinds of lights. During early morning and late evening, the daylight color changes quickly and significantly (although your eyes don't notice, your camera will). Do regular white balances during these periods.
You will need:
· A camera with a manual white-balance function. There should be a "white balance" button or switch on your camera.
1. If your camera has a filter wheel (or if you use add-on filters), make sure you are using the correct filter for the lighting conditions
2. Point your camera to a pure white subject, so that most of what you're seeing in the viewfinder is white. Opinions vary on just how much white needs to be in the frame - but we've found that about 50-80% of the frame should be fine (Sony recommends 80% of frame width). The subject should be fairly matte, that is, non-reflective.
3. Set your exposure and focus.
4. Activate the white balance by pressing the button or throwing the switch. The camera may take a few seconds to complete the operation, after which you should get a message (or icon) in the viewfinder.Hopefully this will be telling you that the white balance has succeeded - in this case, the camera will retain its current color balance until another white balance is performed.If the viewfinder message is that the white balance has failed, then you need to find out why. A good camera will give you a clue such as "color temperature too high" (in which case change filters). Also try opening or closing the iris
a little.

Video Camera Shutter
The term shutter comes from still photography, where it describes a mechanical "door" between the camera lens and the film. When a photo is taken, the door opens for an instant and the film is exposed to the incoming light. The speed at which the shutter opens and closes can be varied — the faster the speed, the shorter the period of time the shutter is open, and the less light falls on the film.
Shutter speed is measured in fractions of a second. A speed of 1/60 second means that the shutter is open for one sixtieth of a second. A speed of 1/500 is faster, and 1/10000 is very fast indeed.
Video camera shutters work quite differently from still camera shutters, but the result is basically the same. (The technical difference is that, rather than using a mechanical device, the shutter speed is adjusted by electronically varying the amount of time the CCD
is allowed to build a charge. If this means nothing to you, don't worry. It really doesn't matter how the shutter works, it's the effect it has that counts.)
The shutter "opens" and "closes" once for each frame of video; that is, 25 times per second for PAL and 30 times per second for NTSC. Thus, if a camera has its shutter set to 1/60, each frame will be exposed for 1/60 second. If the speed is increased to 1/120, each frame will be exposed for 1/120 of a second.
The main effect of higher shutter speeds is that individual frames appear sharper, due to the minimization of motion blur. Motion blur occurs when the subject moves within the frame while the shutter is open. The less time the shutter is open (i.e. the faster the shutter speed), the less movement will take place.
One side-effect of higher shutter speeds is that movement appears jerkier. This is because motion blur tends to smooth consecutive frames together.

Higher shutter speeds are common in sports coverage. Watch any fast-action sport to see the "flickering" shutter effect. Notice how the slow-motion replays look, especially when they freeze the last frame.
Note: As a result of the reduced exposure time with high shutter speeds, the image may appear darker unless the iris
is opened to compensate.


josh thomas said...

im commenting first

Nolan said...

i thinbk you should blog ALL of our notes to make our lives easier. that would be really cool and would help us in our social lives. haha

Grantfree035 said...

hey this is nice information! :)

Lil BooDoo said...

Ms. M is the BEST thing to happen in journalism!

samjay =D said...

Thanks for the notes Ms. Merrill.

sadatel said...


i like how u'r putting notes on your site that way we can acess them from home too. How Inspiring! ;)