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Setting Up a Shot: Difference between revisions
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== Exposure == | == Exposure == | ||
This determines how | This determines how bright the image is. It is done by controlling '<u>Shutter Speed</u>' and '<u>Iris</u>' (referred to as 'aperture' in still photography). | ||
Shutter speed / angle, is the amount of time that each frame of the footage is exposed to the light entering through the lens. As a speed, it measures the physical time in divisions of a second that the frame is exposed for. This will be familiar to those who have used stills cameras before. | |||
As an angle, it actually describes a piece of vintage photography from the genesis of film making. The shutter for a motion picture camera was controlled by a number of spinning disks with wedge cutouts in them allowing light through to expose onto the film. The angle of these cutouts determined the effective shutter speed of the camera. On modern cameras of course, this is all digitally controlled and can be set to the nearest 15 degrees (from 15 to 360). | |||
YSTV almost always uses a shutter speed of 1/50th of a second, or 180 degrees if using shutter angle. This is because it is usual to broadcast at 25fps (which YSTV also does) and the normal shutter speed for shooting is to shoot at a shutter speed of twice the frame rate. I.e. so that each frame of the footage is exposed for half of it's interval. This results (at 25fps) in a shutter speed of 1/50th or 180 degrees (which would expose the film frame for half of its time as it passed through he plane. | |||
180 degrees (1/50th) is a good rule of thumb for ~80 of content. There are situations where changing the shutter speed to ~1/60th is advisable: | |||
* You're filming something that moves ''really'' fast and want the footage to blur less. If the view is still light enough after increasing the speed, go for it. | * You're filming something that moves ''really'' fast and want the footage to blur less. If the view is still light enough after increasing the speed, go for it. | ||
* To stop on-screen monitors flickering, increase the shutter speed to | * To stop on-screen monitors flickering, increase the shutter speed to 1/60th. (Computer video pretty much always draws at 60Hz.) If the shutter speed is not on the main menu; you have to enter the detailed menu to alter it. See the camera operation documentation or see production or technical people. | ||
* Filming on a green screen, shooting at a faster shutter speed reduces motion blur and so make s the key cleaner and faster | |||
Alternately, raising the shutter angle to ~300 or so works very well for a dream sequence or other artistic effects where a lot of blur is desirable. | |||
The iris is a physical barrier inside the camera which can be opened or closed (by internal motors) to change the amount of light that actually enters the lens and thus arrives at the shutter. In most lenses they are formed from at least 6 blades which expand and contract to increase or constrict the size of the central hole which allows light to pass. | |||
Everybody has their own rules for ideal aperture settings and the effect intended will also influence the aperture setting of choice. Also, some lenses have a range of minimum aperture across their zoom or have aperture. | |||
The general effects are: | |||
* Lower F stop numbers (the term used to represent the current aperture) cause more Bokeh (blurry background past the point of focus) and a smaller depth of field (depth of the area in focus on the subject). Higher F stop numbers have the opposite effect. | |||
* Lower F stop numbers introduce more light into the image, bigger central hole so more light, and higher F stop the reverse. | |||
== White Balance == | == White Balance == | ||