EXPOSURE BASICS

OVER EXPOSED UNDER EXPOSED?

OVER AND UNDEREXPOSED: DEFINED The exposure related decision made can affect your image in a number of different ways. For example: When you turn out the lights in your house during the day, you won't be able to see as well as if the lights were on; therefore… your vision is UNDEREXPOSED. Conversely, when the doctor shines a bright light straight into your eyes, you won't be able to see at all because your eyes go into overdrive, thus causing your vision to be OVEREXPOSED.

OVER AND UNDEREXPOSED: DEFINED A digital image sensor works the same way, if an image is underexposed ( bad lighting, bad exposure settings) then your image will be too dark. The same thing goes for images that are overexposed. Both under/over exposure are always a cause for concern in picture taking. Lets figure out how to perfect over coming this issue.

EXPOSURE CONTROL MECHANISMS The Shutter and Aperture both do what? - Control the amount of light that hits the image sensor. Shutter Speed, is the measure of how the long the shutter stays open, as measured in seconds. Often it is in fractions of a second, 1/60th…1/125th…ETC. A faster shutter speed would let in LESS LIGHT.

EXPOSURE CONTROL MECHANISMS In an SLR, the shutter is composed of two curtains. The first curtain opens to expose the sensor. The second curtain follows to close the opening.

EXPOSURE CONTROL MECHANISMS On many P&S cameras, there is no mechanical shutter, instead the sensor is simply turned on for the desired amount of time. With no shutter moving around, you can capture a picture with no sound. The second mechanism for controlling light is a mechanical iris (APERTURE) The iris in your camera is composed of a series of interlocking metal leaves. The wider the iris (APERTURE) the more light gets to the image sensor.

SHUTTER SPEED Measured in seconds. Range from 30 seconds to 1/8000 of a second. The shutter speed display on your camera shows the denominator part of the current shutter speed, so if you see “100” then the camera is set to 1/100th of a second. So 1”6 would be… 1.6 second(s)

SHUTTER SPEED Most cameras top out at 30 seconds, however some cameras have the ability to access the “Bulb Setting” Usually indicated by the letter “B” on the camera. This mode allows you to have the shutter open for longer than 30 seconds.

Aperture Measured in f-stops. Usually fractions, such as 5.6, 2.4, 3.1, ETC… An f-stop is the measure of the ratio of the focal length of the lens to the size of the aperture. Typical f-stop is 5.6

LESS IS MORE f – stops can be a little intuitive (intuition) to the way they are measured. A larger f – stop number indicates a smaller opening. The higher the number, the smaller the opening.

LESS IS MORE When you chose a higher f stop number the aperture stops more light. With a lower f stop number, the aperture is larger and thus lets more light into the camera.

LESS IS MORE Not all lens can open up to the same aperture. The maximum aperture that your lens can open to will be written on the front ring of your lens. If you look at the front of your lens, where the brand name and a bunch of numbers are printed, you might see something like “1:3.5-5.6.” This tells you the aperture range, from full wide to full telephoto. Full wide = 3.5 Full telephoto = 5.6

TWO WAYS TO CONTROL LIGHT You can change the speed of the shutter, and you can change the size of the opening of the aperture. But, you can play with just one of those features to bring about something in your photo. For example, if you want to take a picture of cars going by, make sure to have a SLOW shutter speed, as this will make the cars look blurry that are going by.

HOW SHUTTER SPEED AFFECTS YOUR IMAGE As you speed up your shutter speed, you gain more ability to freeze the motion in your scene. When you leave the shutter open for a longer amount of time, you gain more ability to have the motion blurry in your scene. When taking a picture of a moving car, it is always best to have a slower shutter speed, because the blurriness of the car lets us know that it is In motion. If you took that picture with a fast shutter speed, it would make the picture more clear, but we would not see the car in motion.

HOW APERTURE CHOICE AFFECTS YOUR IMAGE As you go to a smaller aperture, the “depth of field” in your image gets deeper. REMEMBER, depth of field is how much of your image is in focus. Depth of field, is measured around the distance at which you are focused. An aperture that gives you 10 feet depth of field, will give you 10 feet deep of focus.

HOW APERTURE CHOICE AFFECTS YOUR IMAGE Focus is not always evenly centered on your focus point. At very close distances, D.O.F. will extend equally in front of and behind your focus point. As the distance from your point of focus increases, the D.O.F. will increase more behind your subject. ONE THIRDS/TWO THIRDS RULE: about one third of your available depth will be in front of the point of focus and the two thirds will be behind it. D.O.F. = Depth of Field

HOW APERTURE CHOICE AFFECTS YOUR IMAGE Remember to keep the background of your photo soft, the sharper the back ground, the less focus will be on the subject of your photo. If you chose a larger aperture you’ll create a softer background that will bring more attention to the subject of the photo.

HOW APERTURE CHOICE AFFECTS YOUR IMAGE Every lens has an aperture “sweet spot” If you stop down too far you might suffer a noticeable sharpness penalty. This softening occurs because as light rays pass through a small opening, they begin to diverge and interfere with one another. This keeps them from all focusing on the appropriate location.

SHUTTER SPEED/ APERTURE BALANCE As you already know, slowing down the shutter speed while taking a photo of a moving object creates blurriness. Thus most likely causing the photo to be… OVEREXPOSED. You can fix this issue by using a smaller aperture. Conversely if you need a fast shutter speed to stop motion, then you can open the aperture wider.

RECIPROCITY Earlier you learned that a stop (f stop) is a measure of light. When you double the amount of light that hits the sensor, we say that you increased the amount of light exposure by one stop. SHUTTER SPEEDS 1/60 1/120 1/250 1/500 1/1000 1/2000 1/4000 What do you notice about these shutter speeds?

RECIPROCITY APERTURES ( F STOPS) F4 f5.6 f8 f11 f16 f22 Each one represents an opening that’s twice as big as the previous one. In other words, there’s a difference of one stop of light exposure between each successive aperture in this list.

RECIPROCITY

RECIPROCITY Lets say your camera recommends an exposure of 1/500th of a second at f8. Obviously your camera does not make any creative decisions for you, so your camera will try to recommend a shutter speed and aperture combination that will give you a sharp picture. Please do not forget the ONE goes UP the OTHER goes DOWN principle.

RECIPROCITY If you increase your shutter speed from 1/500 to 1/1000 you’ll run the risk of darkening the image, but you can increase the aperture from f8 to f5.6.