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Understanding i--SPEED
i--SPEED
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View Finder
In contrast with some other manufacturer’s products, the Olympus
i--SPEED
camera presents the live image on the CDU or monitor
screen at all possible times. Some menus do require the image to
be obscured and the splash screen logo is used for this purpose.
Also, the playback screen is used to display the contents of the
memory buffer, rather than a live image. During the live view and
the record process, however, the screen will display a live, colour,
real time image, updated at 60 frames per second.
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Lenses
The choice of lens can make a dramatic difference to the video
images obtained.
Choosing the lens must begin with the focal length, which is
expressed in mm. A lens with a large focal length would normally
be chosen when a small area is to be viewed or the camera is to be
a long distance away from the scene, because a longer focal length
means a greater magnification. This type of lens has the
disadvantage of reducing the apparent distance between objects
which are arranged axially with the camera. This is called
foreshortening. Lenses with long focal lengths also tend to have a
smaller maximum iris setting (higher f number) and are dimmer
than short focal length lenses.
A lens with a short focal length is chosen when a wide area is to be
viewed, or the camera is to be placed near to the scene. Lenses
with a very short focal length have the disadvantage of distorting
the perspective of the image and this is called barrel distortion.
Normal lenses have a controllable iris or aperture. The iris controls
the amount of light available to the camera. The higher the f
number, the less light the lens transmits. Increasing the number by
1.4 times (e.g. from f/4 to f/5.6), is called 1 stop and halves the light
throughput.
There is a secondary effect of reducing the iris (increasing the f
number) and this is an increase in the depth of field. This means
that the lens is more able to focus on close and distant objects
simultaneously, so a small iris setting is advantageous.
This is in conflict with the normal HSV requirement for as much light
as possible, especially at high speeds and fast shutter times.
Probably the greatest art in lens set--up is striking a balance
between getting all objects in the scene into focus and having a
bright enough image. It is advisable in general to operate with a
smaller iris (higher f number) and add more light.