The f-number, or f-stop, is related to the aperture in the camera which adjusts the amount of light let in. The two reasons to adjust a camera's aperture are light control and how much of the photo is in focus (depth of field). Determining the right f-number can be tricky but with practice gets easier.
Instructions
1. Locate the f-numbers on your camera's lens. The f-numbers available to you can differ depending on your lens. You will most likely have a range similar to the following: 1.8, 2.8, 4, 5.6, 8, 11, 15, and 22.
2. Remember that the smaller the f-number, the larger the opening or aperture that will let light into the camera. The larger the f-number, the smaller the opening or aperture.
3. Consider the light as you take a picture. If it is bright, you will need less light and can try an f-number of 11. If it is dusk, or indoors, you will need more light and should try an f-number of 5.6.
4. Consider the picture you are taking. Do you want the subject in sharp focus and the background out of focus (shallow depth of field)? Or do you want the entire photo in focus, like in a landscape (greater depth of field)? For a shallow depth of field you will want to choose a lower f-number, like 5.6. For a greater depth of field, choose a higher f-number, like 16.
5. Practice by setting your f-number to 5.6 (large aperture) and take a photo. You will have a shallow depth of field in this photo-meaning there will be a narrow zone in the picture that will be in focus. You will also have a larger opening, allowing in more light.
6. Look at your photo. If it is dark, you will need to select a smaller f-number (larger opening) the next time you take a photo in similar conditions in order to let in more light. If it is too bright, or washed out, you will need a higher f-number (smaller aperture) the next time to reduce the amount of light in the picture.
