Transcript
Camera Settings
1. Shutter Speed
2. Aperture
3. I.S.O.
Shutter [shut‘ter] The Shutter is the part of your camera that opens and closes to allow light onto the sensor or film. In the closed position no light is allowed into the light sensitive part of your camera. In the open position light is allowed through to expose the image. The image varies greatly depending on how long the shutter remains open.
Shutter speed [shut‘ter speed]
Common Shutter speeds:
Shutter speed refers to the specific length of time that the shutter remains open, allowing more or less light into the camera. A longer shutter speed allows more light for low light conditions while a faster speed requires more ambient light such as bright sunlight or strong external lights or a flash.
B, 1min, 30 sec, 1, 1/15th sec, 1/30th, 1/60th, 1/125th, 1/250th, 1/500th, 1/1000th
1/60th of a second is a standard speed appearing orange on this dial because it is the default speed for the flash. This setting is commonly used for portaits and landscapes and can be hand held. B stands for Bulb. In this setting the shutter remains open as long as the shutter release is held down.
1/1000th of a second is a fast setting often used for sports photography or capturing nature. Moving objects appear to be frozen in time with a clear focus.
Slow shutter speeds Long exposure times such as 30 seconds or more allow more light into the camera and can be used to compensate for low available light. Typically a tripod is used when shooting at these speeds, otherwise everything will be affected by a motion blur. The photo above was shot with a 1 minute exposure time using a tripod. People standing relatively still during the exposure appear slightly out of focus while people walking or cars driving by are nearly invisable. The impression left by the taillights are seen as streaks of light.
Fast Shutter speeds Very short exposure times such as 1/500th of a second or less allow less light into the camera and can be used to freeze the motion of things that are moving. Because the shutter remains open for such a brief period of time, more light is required. Fast shutter speeds do not require a tripod. Absent sunlight, a flash or lighting setup is recommended when shooting at high speeds.
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Aperture
[ap•er•ture]
The word Aperture is derived from the Latin : Apertura, which can be translated roughly as opening or window. In optics, an aperture is a hole or an opening through which light travels. The aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane.
Depth of Field
The aperture determines how collimated the admitted rays are, which is of great importance for the appearance at the image plane. If an aperture is narrow, then highly collimated rays are admitted, resulting in a sharp focus at the image plane. If an aperture is wide, then uncollimated rays are admitted, resulting in a sharp focus only for rays with a certain focal length. This means that a wide aperture results in an image that is sharp around what the lens is focusing on and blurred other wise. This anomolly is known as: Depth of Field.
Common Aperture F-Stops:
1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 44, 64
Using the F 8 Aperture setting we can follow the depth of f ield chart on the lens to see how much of our image at a given focal point will be in focus. In this case focused to just beyond 1.9 meters, our image will remain in focus between 1.5 meters and 2.5 meters. Thus with this setting the same image to the lef t will now look different because the boys in the far yard are beyond the focal range of this setting rendering them out of focus in our image below. The fence and the boy, however, remain within the focal range of this setting thus we see them in focus.
By using a high aperture setting such as F22, Deep Depth of Field can be achieved. This means that objects on different focal planes, or different distances from the camera lens, all appear in focus. In the image above; the face of the boy, the fence, and the kids in the yard are all in focus. The F-stop is set by turning the aperture ring to the green line. Notice in the lens to the right that this closes the Iris down to a small opening.
In this f inal image, shot with a low F stop such as 1.4, we see that not only is the distant yard out of focus but now the fence in between is also beyond the range of focal acuity. This type of image is known as: Shallow Depth of Field Depth of Field (D.O.F.) is determined by these four factors; camera-to-subject distance, the lens focal length, the f-stop, and the format size or circle of confusion criterion. Each of these factors affect the focus of an image in different ways and each is altered by changes made to the other factors. The camera to subject distance is f ixed at the time of exposure. It usually involves a range of distances that will be in focus followed by a series of distances with decreased focus as they expand in distance, further and closer from the lens. The lens focal length is determined by the size and shape of the lens. Some lenses are created for up close photography (Macro Lenses) while others are designed for far away (Telephoto). There are narrow angle lenses and wide angle lenses, f ixed lenses and zoom lenses. The focal range is notated as a single numeric value for f ixed lenses(50mm) or a range between two numeric values for zoom and compound lenses(15-200mm).
The F-stop like the Pupil of the Human Eye, is determined by the size of the opening created by the Iris. The smaller the pupil the greater the D.O.F. In optics, the f-stop (sometimes called focal ratio) of an optical system expresses the diameter of the entrance pupil in terms of the focal length of the lens; in simpler terms, the f-stop is the focal length divided by the “effective” aperture diameter. It is a dimensionless number that is a quantitative measure of lens speed. In optics, the circle of confusion is an optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source. For most people Visual acuity at the closest comfortable viewing distance, termed the near distance for distinct vision , is approximately 25 cm. At this distance, a person with good vision can usually distinguish an image resolution of 5 line pairs per millimeter.
The Format size refers directly to the size and shape dimensions of the light sensitive focal plane. In the human eye this would be the retina. In a 35mm f ilm camera these dimensions are set by size of the shutter opening and the f ilm dimensions. In a digital camera the Format size refers to the image sensor or CCD chip. Today, most digital still cameras use either a CCD image sensor or a CMOS sensor. Both types of sensors accomplish the same task of capturing light and converting it into electrical signals.The aperture also determines how many of the incoming rays are actually admitted and thus how much light reaches the image plane (the narrower the aperture, the darker the image for a given exposure time).
Diag ram showing different Format Dimensions
I.S.O. In traditional f ilm photog raphy I.S.O. (or ASA) refers to the sensitivity of a given f ilm’s emulsion to light. In Digital Photog raphy I.S.O. refers to a given range of sensitivity of the image sensor to light.
Common I.S.O. Film Speeds: 50, 100, 200, 400, 800, 1600, 3200
I.S.O. is measured in numbers that double as each grade of f ilm increases in it’s sensitivity (50, 100, 200, 400, 800, 1600, 3200). The lower the number, the lower the sensitivity of the f ilm, and the f iner the grain of the f inal negative. The Higher the number, the coarser the grain resulting in a lower resolution image but increasing the range of acceptable low light.
Digital I.S.O. variation is acheived by adjusting signal gain to the Image sensor. By amplifying the electric signal to the sensor an increase in light sensitivity is obtained. The tradeoff for this increased sensitivity is an increase in the signal to noise ratio.
This image was shot with a Fast, Coarse Grain 1600 I.S.O. f ilm, notice the lack of resolution and value.
CCD Image Sensor
This Image was shot using a slow, Fine Grain 50 I.S.O. f ilm, allowing a very High resolution that shows a wide range of value and details in the image
Example of a Fine Grain Film (50 I.S.O.) by Ansel Adams “ Moon and Half Dome ” 1960
Image Sensor Dissection The size of the Silver Halide Granules in the emulsion dictates the Film Speed and it’s resulting Resolution
Example of a Fast Film (1600 I.S.O.)
Robert Capa 1936 “ Death of a loyalist Soldier”
