The Science of Photography 2 *

The Science of Photography 2



Camera Settings

ISO, fstop, shutter speed, focus area, exposure, EV +/-, white balance, RAW, jpg, are just some of the settings you will encounter when using a DSLR camera (and even modern cellphone cameras). For this discussion I will assume we are using a modern DSLR camera. Keep in mind that for every setting on a camera there will be another setting that will be affected if you change that setting. The combination of settings is what gets you the final correct picture.  I will explain the settings one at a time 

1.   ISO - You will see this setting on every DSLR camera. ISO stands for "International Organization for Standards". This setting determines the camera's sensitivity to light. The lower the number the better the picture but also the longer the camera's shutter will need to be open to get a correctly exposed picture. If you have a lot of light this setting can go as low as 50 but if there is very little light (and depending on the camera) this setting can go up into the thousands. The price you pay for high ISO settings is a picture that is "noisy" a term used when you see a picture that looks "soft" and not sharp.

2.   fstop or focal length - Every lens has a built-in iris that can open and close to let in more or less of the subjects reflected light and "expose" the digital sensor.  When the fstop number is small e.g. f2.8 (a smaller number is a larger opening) and you are focused on the subject the distance that is in focus in front and back of the subject is very small. The background of your picture will be gradually out of focus and sometimes like in portraits this is desirable as it makes the subject stand out. When the fstop is a large number e.g. f22 the subject and most of the foreground and background are all in focus. The price you pay for these settings is this, a small fstop number opens the lens up wide for the light from your subject thus the speed your shutter opens, and closes can be very fast. This is why a lens with a very small f stop number, or "focal length" is called a "fast" lens. Typically, a lens is described by the widest f number it can achieve. A 35mm f2 lens is very fast and good in low light situations. It is also more expensive as the glass required to build it is larger in diameter 

3. Shutter Speed - The shutter is typically located inside the camera body behind the lens. Its job is to open when you push its button to allow the light and image pass through the lens and onto the digital sensor (for a film camera the digital sensor is the same as the film). The length of time the shutter is open will determine the correct exposure the sensor sees. Too much time open and the picture will be too light, too little time open the picture will be too dark. The combination of how wide the iris in the lens (fstop) is set and the time the shutter is open will determine the proper exposure (or amount of light and image) is cast on the digital sensor in the camera.

4. Focus - Most modern cameras have two options for focusing, manual and auto. Most of the time you would leave the camera on auto focus as the camera's electronics does a very good job of focusing on the subject you are shooting. In some cases manual focus may work better an example being if you're shooting a subject that is on the opposite side of a window the auto focus may try to focus on the window even though you're pointing at the subject. In this case you would switch to manual focus and concentrate on getting a sharp subject. Also most cameras will allow you to choose a "focus area" all the way from wide to pinpoint. Wide would be where you want everything in the frame to be in focus and pinpoint (or just a small area) would be when what is important is what part of the subject is within the box. A good example is if you were shooting an animal or even a person it's usually important to have the eyes in focus. For this you would set the "focus area" to pinpoint (or very small box) and make sure the eye is in focus. 

5. Exposure - The "proper exposure" is not a setting but rather the result of all the camera's settings. Proper exposure means you have adjusted all the settings to be sure you achieve the proper balance of details in your photo. If the exposure is correct you will get a good photo that shows all it's properties in balance. A good balance means the photo is as close to the actual scene as possible. 

6. EV +/- - Most cameras have an EV(Exposure Value) plus or minus setting. This is a very important setting and needs to be understood as it can make or break a photo. When electronic sensors in a camera have balanced the fstop and exposure time to get a properly exposed shot it does so by looking at the whole picture in the frame (with some exceptions discussed later). If the picture in the frame has a high contrast area the camera's electronics may be fooled as it tries to get a good exposure for the whole photo. An example is, say you are looking at a photo of a person that is standing in front of a white background (like snow). The person may be taking up 30% of the photo while the snow is the other 70%, so the camera will be basing the exposure on the snow or 70% of the scene. The electronics in the camera will dramatically close the iris (fstop) in order to shoot the snow properly, but you want to expose the person correctly even if it means the snow which is less important is overexposed (too light). This is where the EV+/- setting comes in. The EV+/- setting "cheats" the camera's electronics and allows you to manually get the correct exposure for the person. In this case you'd set the EV+/- setting toward the + side, so the camera will expose the person properly. The opposite of this would be taking a photo of the moon at night. The surrounding area of the moon would be very dark, so to get the proper exposure of the moon you'd set the EV+/- toward the - side to close the iris (fstop) thus getting the correct photo of the moon while the surrounding dark are isn't as important. The degree to how much you set the EV+/- too depends on how much contrast there is in the photo. A person standing in front of a gray background may not need much EV correction at all.