Digital SLR Camera Lenses Explained
Digital Photography – F Stop Explained
When you are using a camera, the media you are recording the image to is fixed in the amount of light required to create the image. This is referred to as the ISO, or speed, and is represented by a number such as ISO 400, 200, etc. The exposure to the light is controlled by the shutter speed and the aperture f/stop. This is a simple explanation of the f/stop mechanism.
First one must understand that the shutter speed and f/stop directly affect each other. The slower the shutter speed, the longer the exposure to the light. So, in order to prevent flooding, or overexposure, of the medium, the amount of the light must be reduced. This is done using the aperture, or f/stop, by decreasing the amount of area of the lens that is open to the light. The inverse is also true, if you wanted to take a photo of an athlete in motion but wanted very clear, crisp photos, you could use a very fast shutter speed, and a very wide aperture.
Now you know what it’s used for, here’s what the f/stop numbers mean. The numbers printed on your camera lens can range anywhere from f/1.0 to f/128, but this isn’t all of them, by any means. This number represents the ratio between the focal length of the lens, and the diameter of the aperture opening. For example, a 50mm lens with a 25mm aperture is a f/2 lens, and a 100mm lens with the same 25mm aperture setting is a f/4. Most every lens manufactured today has several f/stop adjustments available to the photographer, but the values printed on the barrels may be a rounded off, for simplicity.
For this example, keep the above in mind. If a person wanted to fill a container with water, but the container had a small hole at the entrance, the flow of the water must be reduced. This will require more time to fill the container, but if the opening is larger, the flow can be increased, thus allowing for faster filling. So, if the shutter speed is slow, i.e. 1/8, the f/stop number must be increased to allow less light in, to prevent overexposure. The opposite is true if the shutter speed is perhaps 1/125th the f/stop number should decrease, to allow more light in. This means that if the bottom number i=on the shutter speed gets bigger, the f/stop number should get smaller.
One last thing that should be mentioned is that the wider the aperture rating on a lens, the more expensive, and bulky they tend to be. there are lenses on the market, both new, and used, with maximum apertures of f/1.2, and as low as f/.95, but the costs of lenses like these can be prohibitive. That coupled with the fact that the f/.95 lens requires the use of a tri-pod, make these almost exclusively professional equipment.
About the Author
David Chappell is the owner of SLR Lens Depot – Camera Lenses for Sale, Reviews, and More. A website featuring digital photography guides, lens reviews, lenses for sale, news and much more.
canon slr digital camera reviews explained,canon slr digital camera reviews