Miranda G
Recognized Leader / Outdoor Photography
- State
- Virginia
Since some may not be familiar with some of the photography terms that have popped up on previous threads, I would just like to focus on a few common ones and provide a quick explanation on what they are, and what they mean to you as a photographer. F-stop (also known as f-ratio, or focal ratio) is just a fraction. It tells you how open or closed the aperture of your lens is, and how much light you are letting in to create your image. In most of our cases, the light is exposing a sensor to create the image. In a film camera, the film itself would be exposed instead of a sensor.
So if you think of the aperture as the pupil of your eye, it might make more sense. The wider the opening, the more light is getting in. The f-stop number is based on a math formula that puts the diameter of the aperture over the focal length of the lens.
A lens with a 200mm focal length and an aperture diameter of 50mm would give you a ratio of 200/50 which ends up being f4. As you can see from the illustration, the smaller the f-stop number, the bigger the aperture opening, and the more light entering the lens. Each stop has half the light gathering area as the previous one.
Common f-stops, and their relationship to each other
The lens will determine what options exist for aperture openings. Many lenses have the widest aperture at f4. Typically lenses go all the way down to f22 or f32.
The choice of aperture depends on what sort of effect you wish to give a photo. Specifically what sort of depth of field you wish to show in your image. The more open the aperture, the shallower the depth of field. You may want a shallow depth of field to pick out a single detail of a flower as I have done here.
f 1.8 Exposure: 1/200 sec.
Or you may want to have more depth of field and have more things in your image in focus.
f 8 Exposure: 1/60 sec
The same subject again, with a wider aperture setting.
f 2.8 Exposure: 1/200 sec
This is the same flower shot with 2 very different aperture settings. Hopefully this helps illustrate the difference. Typically things like landscapes are shot with a narrower aperture.
So if you think of the aperture as the pupil of your eye, it might make more sense. The wider the opening, the more light is getting in. The f-stop number is based on a math formula that puts the diameter of the aperture over the focal length of the lens.
A lens with a 200mm focal length and an aperture diameter of 50mm would give you a ratio of 200/50 which ends up being f4. As you can see from the illustration, the smaller the f-stop number, the bigger the aperture opening, and the more light entering the lens. Each stop has half the light gathering area as the previous one.
Common f-stops, and their relationship to each other
The lens will determine what options exist for aperture openings. Many lenses have the widest aperture at f4. Typically lenses go all the way down to f22 or f32.
The choice of aperture depends on what sort of effect you wish to give a photo. Specifically what sort of depth of field you wish to show in your image. The more open the aperture, the shallower the depth of field. You may want a shallow depth of field to pick out a single detail of a flower as I have done here.
f 1.8 Exposure: 1/200 sec.
Or you may want to have more depth of field and have more things in your image in focus.
f 8 Exposure: 1/60 sec
The same subject again, with a wider aperture setting.
f 2.8 Exposure: 1/200 sec
This is the same flower shot with 2 very different aperture settings. Hopefully this helps illustrate the difference. Typically things like landscapes are shot with a narrower aperture.
