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- One of 47 entries in the i3m blog (34 before this & 12 since).
F-Stops explained
- May 13, 2009, 5:46 pm
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Basic photography principles: Part I – F-Stops explained
Chances are that if you’re reading this then you are already a DSLR (digital single lens reflex) owner and are starting to move away from the nice comfortable ‘everything at automatic’ setting on your camera. Steady!
If you’re an expert or experienced photographer already then an introduction to aperture and stops is going to be something you’re already familiar with but along with the previous blog ‘Camera modes explained’ this forms the foundation of some forthcoming photography blog articles which we are working on.
Stops explained
So, once more into the world of photography that isn’t point and click! Let’s start with Stops (so to speak!) Stops are a measure of the lens aperture and control the amount of light entering into our camera through the lens. Too much light and we get an over exposed image, in which case we need to increase the number of stops in order to reduce the amount of light falling on our cameras sensor. Stops are quoted as an f number, for example f8. The bigger the f-stop the smaller the aperture is set to and hence the less light entering the camera through the lens. All lens manufacturers give their lenses an f rating, which is its maximum.
Basically that’s Stops explained and you can quite happily walk away with this knowledge and no need for anything more technical. Or we can go on to give an explanation of what an ‘f’ actually is and that’s going to require some basic maths! In our example we used an f8 but what is f8? Well, it means that the diameter of the aperture is set to 1/8 of the focal local of the lens. So a 100mm lens set to an f stop of f8 would have an aperture diameter of 12.5mm (100 x 1/8). Well, historically it wouyld anyway. Back in the days when a 100mm lens was a 100mm tube with an element at the end. The fractional f-stop dates back to the days prior to multiple element lenses used in modern DLSR cameras!
So how does this relate to our photography? Well, in automatic the camera will stop down the lens to what it considers the best setting for an average photo. By moving out of automatic we can halve or double the amount of light entering our camera by adjusting through the range of available stops. Different conditions will determine how much exposure we need and what f-stop setting for our lens. In our case we are looking at night photography where we need to set our f stop down, increasing the lens aperture and allowing more light in low light, night time, conditions.- 'Chances are that if you’re reading this then you are already a DSLR (digital single lens reflex) owner and are starting to move away from the nice comfortable ‘everything at automatic’ setting on your camera.'
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