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Tutorials :: A Beginner's Guide to Simple Photography Concepts: ISO, Aperture, and Shutter Speed
A Beginner's Guide to Simple Photography Concepts: ISO, Aperture, and Shutter Speedby redsunphotography
There are 3 things that affect your image quality in photography; ISO, aperture and shutter speed. All 3 of these things depend on one other factor which is light. A photograph is basically a chemical process in which light is exposed to film, or a sensor in digital cameras, and registers an image.
Thereís a device in the camera called the diaphragm, which is directly connected to aperture. The different aperture settings are called f-stops, and are represented by the numbers you see on the image. The larger the number, the smaller the aperture, so for example, an f-stop of f1.4 would be very large, while an f-stop of f16 would be very small. Typically, most consumer lenses have a range of f2 to f16. Donít be overwhelmed by the technical terms and numbers and things like that, once you try everything out on the actual camera, it will all start to make sense. When I first went over the module on this it was all gibberish to me, until I actually took some pictures trying all the different settings. Thatís when it all made perfect sense.
Now, usually a faster shutter speed will require a larger aperture to allow enough light into the camera, and a slower shutter speed will need a smaller aperture to prevent too much light from getting in. You see, shutter speed is how long the shutter is open to allow light into the camera. Shutter speed is always measured in seconds. To demonstrate the effect of ISO, see the below image. Each photo was taken at 1/250th of a second, and the aperture set to f5.6, while the ISO was changed. The ISO is simply how sensitive the film, or censor in a digital camera, is to light. The lower the ISO is, the less sensitive it is to light. The higher the ISO is, the more sensitive it is to light. You can see from the photo, that at 100 ISO, the picture is quite dark. At 400 ISO, the picture is better, and at 1600 ISO, the picture is far too bright. Depending on the ISO you are using, your shutter speed will have to be adjusted to allow the right amount of light for what you want to achieve.
The more light that is available, the faster your shutter speed can be. The type of light will also change things, but that gets more complicated. All light has a temperature in degrees Kelvin, which also affects things. I wonít get into that yet, as itís a little more advanced.
Now, letís talk a little about why shutter speed is important. Itís pretty simple, actually. The faster your shutter opens and closes, the less you have to worry about a blurry image. For most people, a shutter speed of 1/60th of a second is the slowest you can hand hold the camera before experiencing blur due to camera shake. If you are photographing a still object, or a slow moving object, a fast shutter speed isnít as important. If you are photographing a fast moving object, a fast shutter speed suddenly becomes a necessity most of the time. Now remember, the higher the ISO, the more sensitive the film/censor will be to the light. So one might think itís best to always use the highest ISO possible, right? The correct answer is; sometimes. In the next image we see something new, called grain.
Grain is essentially how nice your photos look. Most of the time, you wonít be able to tell the difference in grain at standard print size of 4x6. However, if you ever have a photograph youíd like to enlarge, ISO suddenly becomes very important. The higher the ISO, the grainier your photo will look. Below I cropped just the face of an image, one at 100 ISO and the other at 1600 ISO. The first photo looks smoother, while the second looks, well, grainy. Most consumers wonít need to be making a lot of enlargements, so this doesnít always matter. But even an amateur will sometimes get that one perfect shot they just would love to hang on their wall. Unfortunately, if that perfect shot was taken with a high ISO film, or using a high ISO setting on a digital camera, the size of the enlargement will be limited before it starts to look bad. I find for the average every-day John and Jane Q. Normal, 400 ISO is best. It gets more complicated of course if youíre looking at it from a professional level, and I may get into that another time.
Finally, we get to what most people get lost on, Depth of Field. Letís start this time by looking at a picture.
Most likely, in the first frame, your eye is attracted to the figurine. This is because the back round is blurred, and unobtrusive. In the second frame still focused on the figurine, but a little distracted. In the last frame, your eye was probably drawn first to the red box, and when you look at the figurine, youíre distracted by the box in the center. So as you can see from the pictures, depth of field is essentially the area in front and behind the object that is in focus..
Each photo was taken with the same ISO, but both the shutter speed and aperture were changed. As you can see, the back round became less blurred the smaller the aperture. The entire time I kept focused on the figurine. Anything in front of, or behind the figurine would appear blurry. You can set things up however so that your depth of field is infinite (to a degree) and everything is sharp. The further away something is, the more infinite the focus can be. The closer it is, the more limited that becomes. For example, if taking a macro photo of a small insect, you can have the insect in focus, but no matter what lens or camera you have, you can focus on both the insect up close and mountains in the distance. The closer something is, the more limited the depth of field will be.
Depth of Field is probably the most confusing to beginners, because reading about it can be complicated, as there are many different factors that will affect your depth of field. For example, a telephoto lens will have a more sensitive depth of field, while a wide angle lens will be less obvious. Itís easiest to tackle this one factor by taking your camera out and just trying the different aperture settings and distances from objects. Some cameras will have a depth of field preview button, that will show you in the viewfinder how the depth of field will look. This is a very helpful function to have, but if not, trial and error must be used for the beginner.
The best thing to do is buy or rent an old, fully manual film camera. The biggest problem most beginners face is the ease of automatic features. Buying a fully manual camera forces you to learn these beginner concepts, which will aid greatly in how all you photographs will look in the future. My 2 favorite manual cameras are the Pentax K1000 and the Canon AE-1 (But do not get the Canon AE-1 Program, as it is largely automatic if you want it to be).
The settings for all these functions will be available on most digital cameras, not just SLRís. Chances are if your camera is 3 megapixels and up, it will have the right functions. Youíll have to consult your manual for help on where to find them and how to set them on your camera however.
Next time, I will talk about the basics of composition, exploring things like image placement, shapes and perspective.
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