Yashica Twin Lens Reflex Guide - Focal Press January 1964 Page 36 / 55
Scans and Document copyright by Mischa Koning - www.3106.net
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Shutter Speeds and Movement
The actual shutter speed you need within a series of available aperture shutter speed combinations is governed by
considerations of camera steadiness as well as of subject movement.
An unsteady camera hold results in camera shake. Even the slightest shake will result in inferior definition on the negative.
Practical experience goes to show that 1/125 sec. is safe, while you have to hold tile camera particularly steady when using
1/60 or 1/30 sec. Where lighting conditions make even longer exposure times essential and there is no subject movement,
either support the camera on a tripod or took round for extra support for your elbows and hands - e.g. a wall, railing, etc.
The shutter speed required to arrest movement depends of course primarily on the speed with which the subject moves.
Remember, however, that parts of the subject (e.g. the legs of a runner) may move faster than the subject as a whole; you
may sometimes have to compromise and show such parts slightly unsharp. Often that is not a serious fault, as slight
blurring - provided the main part of the subject is sharp-helps to emphasize the impression of movement.
Other factors to consider are the distance of the subject - the farther away, the less noticeable the movement blur; the focal
length of the lens - a long-focus lens in effect brings tile subject nearer; and the direction of the movement - objects
moving across your field of view blur more than if they are approaching or receding.
The most convenient way of allowing for all these factors is with the aid of a simple table (p. 67).
Aperture and Depth of Field
When you focus the camera on a given object, tile image of that object wilt be really sharp on the film. Things nearer or
farther away will be gradually less and less sharp, until they are noticeably blurred. The range of distances over which
objects are still acceptably sharp, before you do notice tile loss of definition, is known as the depth of field.
You can control the extent of this sharp zone by the lens aperture. As you stop down the lens, the zone of sharpness grows
in both directions; as you open up the lens, it's depth decreases.
You can obtain the actual zone of sharpness at various apertures and distances from depth tables, but in practice the most
convenient way is to use the depth of field indicator. This exists in two types. A special scale of aperture numbers is
marked opposite the distance scale of the Yashica reflex cameras. There are two sets of such numbers from the largest stop
(f3.5) to the smallest (f22) on each side of the focusing index (the mark that indicates the distance to which you have set
the lens).
At any distance setting, the distance figures opposite each pair of aperture numbers on the depth of field scale give the
near and far limits of sharpness. For example, at 10 ft. you may find the two stop values 5.6 on the scale (f5.6) opposite
about 8 and 11 ft. - so you have a sharp zone from 8 to 11 ft. At f3.5, the distances opposite the stop values 3.5 may be 9½
and 10½ ft. respectively: at f11 you might get a sharp zone from 7 ft. to 15 ft.
You will also notice that the depth of field is greater at far distances than at near ones. At 5 ft. and f 5.6 the sharp zone
only covers from about 4½ to 5 2/3 ft. - less than 1½ ft. altogether - against nearly 3 ft. at the 10 ft. Setting.
Two more points on depth of field.
First, the depth obtained depends also on the focal length of the lens. Short focus lenses yield more depth and tele lenses
less depth. As the lens of the Yashica reflex camera is not interchangeable we can ignore this point.
Secondly, the sharp zones obtained by the indicator or tables are based on a somewhat arbitrary assumption of how much
blurring is acceptable. So depth of field data for different cameras with the same lens may not always agree, and you are
also quite safe in rounding off figures obtained from such data. And if you intend to make really big enlargements from
your negatives, you can use stricter standards of sharpness by simply stopping down the lens by one stop.
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