Camera
All cameras from the most basic to the highest end share some basic characteristics.
Lens.
All lenses are made up of specially ground glass layers that are designed to focus incoming light onto a surface to create an image. In digital cameras this is a sensor - which basically change light into an electrical signal. In film cameras, the exposure takes place on, as you probably know, film. A variably sized hole call the aperture is located in the lens. This aperture controls the amount of light passing through lens. The aperture's basic unit of measurement for how much light is getting through is the "ƒ Stop." A whole Stop change in aperture lets in either half as much light or twice as much light. On your lens (or in the view finder, or maybe on an LCD menu on your camera) you typically see numbers like ƒ1.8, ƒ2.8, ƒ4, ƒ5.6, ƒ8, ƒ11, ƒ16, and ƒ22. These are whole Stops which, as previously explained, lets in twice as much or half as much light compared to the Stop beside it.Learn more about aperture with this video.A shutter which limits how much time light is allowed to enter your light-tight box. The measurement for the shutter is the "shutter speed," also known as Stops, which is measured in fractions of a second like 1/30th, 1/60th, 1/125th, 1/250th, 1/500th and so on. You can see a little easier how each might vary the exposure by either half as much light, or twice as much. Exposure times can also vary from 1/8000th of a second to several seconds. Some systems can use up to hours of exposure When hand holding the camera, its important to make sure the shot is not blurry from camera shake. You should have the shutter set to the "same number" as you lens length. For example, if using a 50mm lens, you want a shutter speed of at least 1/60th of a second. If you're using a 135mm lens, 1/125th is okay, but 1/250th would be better. I've found with digital, because most have a multiplier effect (the sensor is smaller than 35mm film, and effectively make the lens 50 per cent longer) you need to set the shutter accordingly. If using a 50mm lens on a digital SLR, I set the shutter to the half stop of 1/90th or faster.If you don't have enough light for the exposure I recommend a sturdy tripod. If you have a questionable speed, you can try bracing yourself against a post, tree, or other stationary object. I never stop from taking the shot even when I'm doubtful, you never know - you might get a great shot anyways. Learn more about the shutter with this video. A light tight box. Holding the lens, shutter and exposure medium, the body of the camera keeps light out. On most cameras, the body also holds electronics to control the aperture and shutter. The meter will help you determine the exposure you need. This is not something you can use on all cameras - particularly very old SLR's and most point-and-shoot style cameras. The meter may be part of the camera's system, but not have any visible meter for the photographer to use. However, most serious cameras do have a display for the meter so you can determine your exposure. The most important part of the camera is the six inches BEHIND the viewfinder (assuming you use the viewfinder, if you normally look at the LCD on the back of your digital camera that would change to about 18 inches.) A note about Stops. On modern cameras, there are numbers for additional fractions of a Stop, which can be either 1/2 Stops or 1/3rd Stops. This makes learning your stops a little more complicated but the principal still works.Almost everything else on modern cameras is a way to control the focus of the lens, the aperture or the shutter speed. On digital cameras there is one last control which is to set the colour temperature. This will be explained later in another lesson. If you're using a modern digital SLR, or a film SLR with a lot of automation on it, I highly recommend you read your camera's manual closely to find out how to do basic control of: setting the camera to manual exposure, setting the lens aperture, and setting the shutter speed. These three areas are important for getting the most out of these lessons. If you are using a pocket camera or point-and-shoot style camera, you can set these features on some but not all cameras of this type. If not, you can skip the exposure control lessons and just do the composition lessons.
Meters and Lighting
Getting a good exposure generally depends on understanding light and using a meter to measure the light in a scene. Reflected light and incident light meters Metering reflected light is exactly what it sounds like - you’re measuring the light bouncing off of the subject. Incident light is measuring the hitting the subject (before it bounces back to the camera.) A meter helps to determine both the aperture and shutter speed. In some cases, the meter gives you a digital read out of the appropriate aperture at a given shutter speed. Some meters - especially older ones - uses a needle which you match to either a line or a second needle. Its a good idea to either get the sales person who sells you the camera or hand held meter to show you how to get the most out of it or can read the manual that comes with the meter or camera. A camera’s internal meter always measures reflected light. In most cameras, this works very well for almost all the scenes most of us shoot. The problem comes when shooting a dark on dark subject or light on light subject. This is covered in other lessons, but the essential idea is that the meter thinks the whole world is 18 per cent grey. So, if you’re shooting a black cat on a dark chair, the meter will think it should be a lot lighter than that and will overexpose the image. Conversely, if you’re shooting snow on an overcast day, the meter will try to darken it to grey and it will underexpose the subject - even more than the usual grey of the day. Or an egg on a white table will come out muddy grays. Understanding that, you can usually change the exposure to be more realistic. Or, you can get a handheld meter which measures the light hitting the subject (incident light) and it doesn’t matter if the subject is white, grey, black, red or any other colour. On most new style hand held meters, there is a white dome covering the sensor which is used for measuring incident light. As a rule, the best way to measure incident light is to stand beside the subject and point the white dome towards the camera. This gives a good overall exposure. You can can also point the meter towards the light (or brightest light if there’s multiple light sources) to absolutely keep from over exposing the scene. This is especially good when doing a portrait. However, if the brightest light is coming from overhead and you’re shooting a portrait, point the meter at the camera or you’ll get deep dark shadows in the eye sockets which will make your subjects look like they have raccoon eyes. If the subject is too far away to easily stand beside, you can find a spot with similar light to that hitting the subject, and measure the light the same way. Spot meter Another type of meter is the “spot meter” which can be hand held or built into many higher end cameras and is useful for more distant scenes you can’t just walk up to and use an incident meter. This measures reflected light, but only in a very small area - typically 1 to 3 degrees which is a small spot in an overall scene. The handheld meters tend to be the tighter 1 degree measurement. With a spot meter, you can determine the brightest point in a distant scene, as well as the darkest. Then, you can average the exposure between the two and hope to keep the highlights and shadows, or you can decide one is more important than the other. Those are choices you have to make yourself. Flash meter Many modern handheld meters include the ability to measure the light put out by a flash system - whether small portable flashes or big studio style flashes. Most photographers use light meters using incident light. Because flashes are very short exposure, the important part is the aperture. In most situations, especially using studio flashes, any other light - such as lamps, etc - will be so under exposed you won’t see the light in the picture. You can, however, also measure any ambient light and adjust the shutter speed to make any background light the same exposure as the flash or slightly under.
Histograms on Digital Cameras
Note: Showing the histogram on the different cameras is done different ways - please refer to your user's manual to find out how its done on your particular camera.
Once you see the histogram, you can either adjust your aperture and/or shutter speed, or the exposure compensation to bring the histogram into line. (Again, refer to your user's manual to find out how to do this if you don't already know.) The right side of the histogram chart is the "highlight" side. The left side is the "shadow" side.
This is properly exposed image:
To make sure you have as much highlight detail as possible, the histogram bars should be as close to the right side (highlight side) of the histogram as possible without blocking up. If the image is underexposed, it can be rescued by lightening it in your editing program, but generally will be gain noise.
Pre-School
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