The Camera System A Quick Overview throughout History In its simplest form a camera as a device has three interacting systems A viewing/Focusing system A light control system Image Reciever System A simplistic pinhole camera has no viewing or focusing system while more complex camera systems allow for adjustment of focus and viewing of the frame. Viewing and Focusing System The most Simplest form of Separate Viewfinder was the plain wire frame called the Sports Finder This would allow a photog. To quickly frame an action shot using a large cumbersome press cameras of the past Viewing Methods Much more common is the separate viewing window used in cameras from disposables to classic and modern Range Finder models Another form of separate view finder is the TLR ( Twin Lens Reflex) TLRs have one lens for viewing and focusing the shot and another for taking the photo Separate View finders can be effective for most shots but can cause problems for close up shots. The most common problem is known as Parallax Error which is a mis-match of what the photographer sees and what the camera actually photographs resulting in part of the image being cut off On cameras that have the ability for interchangeable lenses and a separate view finder the problem of the field of view to the format of the lens occurs Is as close as you can get to what you see is what will be captured on the Image. Single Lens Reflex shows most of what the lens is capturing through a unique use of mirrors and lenses Most SLRs have 92-95% of the image featured in the view finder. The more professional the camera this number can go up to 100% Through- the lens Viewing Systems Much like the through the lens viewing system the electronic view finder will take what the lens is projecting onto the sensor and feature it on an LCD screen Although it is accurate many of the finer details in an image can be lost because of the LCD screen The LCD can also become washed out in sunlight and may not be an effective viewfinder Many camera companies now offer Hoods to allow the photog to see the image in sunlight Electronic View Finders With a through lens camera focusing is also what you see is what you get. The photographer will turn the lens barrel and the image in the view finder will become sharper or more diffused When it is at its sharpest we say that the image is in focus Focusing Methods Some Cameras use aids to help the photographer get the camera into focus. A split- prism is a focusing aid that usually has a horizontal line When an image is out of focus the image will be mis-aligned on either side of the split prism line Manual Focusing Aids Microprism is another form of focusing where the image will be broken up by multiple diamond shapes if not in focus Some cameras have the view finder covered in the microprism diamonds while others will just use a ring of micro prism around a split prism. Manual Focusing Aids Range finders were a style of camera that had a separate view finder. They would be focused by finding out the distance of the subject to the camera Focusing these cameras tended to take two overlapping images or a split image and moving them into alignment Range Finder Focusing Modern day cameras now all have the capability of Auto-focus that will easily focus the image These Auto-focus systems are broken down into Active and Passive auto- focus Auto- Focus Is the system most predominant in point-and-shoot cameras that are being used predominantly for snap shots It sends out an infrared beam that bounces of the subject and then back to the camera The delay of return will allow the camera to calculate the distance and focus the camera for that distance Active Auto Focus Problems arise when the infrared beam is not focusing on the subject Many of the beams go to the center of the image, if the subect is off to the side in a rule of thirds composition, the subject will not be in focus Some cameras will allow you to focus on the subject in center then will lock in the focus so you can set up the composition again Another problem arises in taking action photos of a subject that is changing range distances rapidly It takes a few seconds to go through the auto focusing process Problems with Active Auto-Focus PAF systems are used in very high end professional grade cameras The PAF systems used in todays digital and film SLRs make use of multiple sensors and computer circuitry to quickly and precisly achieve focus under almost any condition The user can also select what sensors or combination of sensors are active Passive Auto- Focus The amount of light that accesses the digital sensor or film is controled by the cameras light control system This system is made up of the lens Aperture and the Shutter These two components can work together or independently to regulate how much light comes in to contact with the light sensitive material Light Control System The word aperture means opening It is a hole that can fixed or variable size depending on the age of the camera Classic pin hole cameras would have fixed apertures It can be located in the camera body or the lens assembly Aperture Two types of varying the aperture size The first is a series of different sized fixed openings Early boxed cameras and even some first generation snap shot cameras were equiped with a rotating plate with two or more opening sizes The photog could rotate the plate to desired size Methods of Varying Aperture Large view cameras of the 19 th century had individual plates with precisley different sized holes cut into the plate The plate would be slid into the camera behind the lens Later a larger single plate with multiple sized holes was used These plates were known as WATERHOUSE STOPS The Diaphram or Iris is a variable aperture device that consists of thin overlapping blades On modern SLRs the iris is mounted in the interchangable lenses and the size is adjusted by rotating a ring on the lens barrels This gives you an infinite amount of different sizes of aperature The second form of varying Aperture On the ring that controls the iris are a series of specific size openings. These are standard sized apertures and are known as F-Stops These f-stops have a constant relationship of doubling in size As the f# gets larger the aperture gets smaller F- Stops The size of the opening has a direct relationship to how much of the picture will be in sharp focus The zone of sharp focus is known as the depth of field The larger the aperture opening the smaller the depth of field will be Aperture and Depth of Field The role of the shutter in the camera is to operate like a valve or faucuet and control the amount of light that contacts the image reciever Most shutters are mechanical and physically open and close They are broken down into two types The Shutter System Located in the lens assembly Usually used in simple, inexpensive small cameras, some medium format cameras, and all large format/ studio cameras The oldest and most simple shutter is a spring loaded disk that would have a hole in it Pressing and releasing the shutter button would create and release tension on the spring which would bring the disks hole into alignment with the aperature Between the Lens Shutters A more complex mechanism that makes it possible to adjust shutter speeds is the leaf shutter It allows the photgrapher to create more or less tension on the springs which adjust the time frame the shutter stays open The leaf shutter These shutters are located in the camera body just infront of the image reciever These are almost universally used in SLR digital and film cameras Consists of two flexible pieces of metal or sturdy cloth known as curtains that slide over the image receiver in sequence. The lag time between the two curtains can be controlled Focal Plane Shutters Shutter speeds, like f-stops have a constant relationship The length of time the shutter is opened doubles as it increases Shutter speeds Shutter speed plays a key role in achieving proper exposure along with the aperture It is also the primary means of controlling camera and subject motion Blurring of a photo due to camera movement is usually always undesirable Blurring due to subject movement has positive and negative aspects Shutter Speed and Motion Control Is the invouluntary movement of the camera during exposure Typically occurs when hand holding a camera at slower shutter speeds Camera Shake
