Photos & Numbers 1
Behold: the f-stop. Why is f-stop called f-stop? I know not. I do, however, find f-stop an awesome nickname. Like, "F-Stop, you so crazy."
Now, f-stop is mathematical, but he makes little sense. The problem is that f-stop is logarithmic.
The numbering for f-stops is standardized, although the numbers themselves are only important in how they relate to each other. Meaning, they do not provide some kind of useful literal information, like shutter speed measures fractions of seconds.
Here's a list I found of most possible f-stops: 0.7, 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64, 90. The smaller the number, the bigger your aperture, which lets in more light.
Not to get too mathematical, but if you look at that sequence, you'll notice that the numerical distance between each one grows as the numbers themselves get bigger, a classic logarithmic relation.
If that doesn't make immediate sense to you, just ignore it and remember this: each successive f-stop lets in half as much light as the previous f-stop. So f0.7 lets in twice as much light as f1.4. And f5.6 lets in twice as much light as f8. So it also follows that f32 lets in half as much light as f22. (Like I said, these are standardized, so it's not like there are lenses built to skip f-stops or something. They always appear in the above order and are always sequential.)
This explains why shutter speeds are also incremented roughly logarithmically, like so:
Adding even more to the confusion is that on most cameras, shutter speeds are written as above, where 1000 = 1/1000 of a second. Luckily, most digitals display it as a fraction for you.
Referring back to this picture, you can see that, on older cameras, the f-stop used to be displayed on the lense itself, right next to the ring that you turned to adjust your aperture. These lenses are fast becoming vintage. Today all the fully-auto-equipped cameras display the f-stop and shutter speed in the viewfinder, and you adjust them with ergonomically placed dials instead of turning the ring. Most digitals show it on the LCD.
Anyways, you can see how the numbers are related. Speaking very roughly — because there will be variation between lenses and depending on the sensitivity of your film or digital equivalent (a whole 'nother post to itself) — a bright, sunny day calls for 1/250 of a second at f16. If you decide you want a longer depth of field, you set the f-stop to 22, reducing the intensity of light by half, and knock the shutter speed to 1/125, doubling the amount of time light is allowed onto the film.
Which f-stops are available to you depends entirely on your lense. For reasons known only to glassologists, it is very difficult to make lenses with really big apertures. With a standard SLR camera — shit, that stands for Single Lense Reflex camera; another effing post to itself; look, it basically means cameras with interchangeable lenses; a Canon Rebel is one common, basic example — it comes with f3.5 – f22 lense. My old high school camera, pictured above, has a lense that is f1.4 – f22. Now, get ready, because newer cameras and lenses can measure fractions of f-stops. For instance, my Optio is f2.8 – f7.9, the latter not being one of those standardized numbers above. Accordingly, my Optio allows more shutter speed increments to match. Anyways, you're going to pay extra money for anything below f3.5, because for photographers, light is The Precious. Anything smaller than f32 is also pretty rare. Ansel Adam's photo clique was called f64, I believe, but that referred to their darkroom procedures, I think. Whatever, Ansel's overrated.
Of course, all this information is useless to the average snapshooter, who points the camera and lets the little automatic gods inside sort it out. But, in posts to come, we'll talk about some simple things you can do using this understanding of f-stops and shutter speeds to really improve your photos. Knowing is half the battle and all that shit.
Now, f-stop is mathematical, but he makes little sense. The problem is that f-stop is logarithmic.
The numbering for f-stops is standardized, although the numbers themselves are only important in how they relate to each other. Meaning, they do not provide some kind of useful literal information, like shutter speed measures fractions of seconds.
Here's a list I found of most possible f-stops: 0.7, 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64, 90. The smaller the number, the bigger your aperture, which lets in more light.
Not to get too mathematical, but if you look at that sequence, you'll notice that the numerical distance between each one grows as the numbers themselves get bigger, a classic logarithmic relation.
If that doesn't make immediate sense to you, just ignore it and remember this: each successive f-stop lets in half as much light as the previous f-stop. So f0.7 lets in twice as much light as f1.4. And f5.6 lets in twice as much light as f8. So it also follows that f32 lets in half as much light as f22. (Like I said, these are standardized, so it's not like there are lenses built to skip f-stops or something. They always appear in the above order and are always sequential.)
This explains why shutter speeds are also incremented roughly logarithmically, like so:
Adding even more to the confusion is that on most cameras, shutter speeds are written as above, where 1000 = 1/1000 of a second. Luckily, most digitals display it as a fraction for you.
Referring back to this picture, you can see that, on older cameras, the f-stop used to be displayed on the lense itself, right next to the ring that you turned to adjust your aperture. These lenses are fast becoming vintage. Today all the fully-auto-equipped cameras display the f-stop and shutter speed in the viewfinder, and you adjust them with ergonomically placed dials instead of turning the ring. Most digitals show it on the LCD.
Anyways, you can see how the numbers are related. Speaking very roughly — because there will be variation between lenses and depending on the sensitivity of your film or digital equivalent (a whole 'nother post to itself) — a bright, sunny day calls for 1/250 of a second at f16. If you decide you want a longer depth of field, you set the f-stop to 22, reducing the intensity of light by half, and knock the shutter speed to 1/125, doubling the amount of time light is allowed onto the film.
Which f-stops are available to you depends entirely on your lense. For reasons known only to glassologists, it is very difficult to make lenses with really big apertures. With a standard SLR camera — shit, that stands for Single Lense Reflex camera; another effing post to itself; look, it basically means cameras with interchangeable lenses; a Canon Rebel is one common, basic example — it comes with f3.5 – f22 lense. My old high school camera, pictured above, has a lense that is f1.4 – f22. Now, get ready, because newer cameras and lenses can measure fractions of f-stops. For instance, my Optio is f2.8 – f7.9, the latter not being one of those standardized numbers above. Accordingly, my Optio allows more shutter speed increments to match. Anyways, you're going to pay extra money for anything below f3.5, because for photographers, light is The Precious. Anything smaller than f32 is also pretty rare. Ansel Adam's photo clique was called f64, I believe, but that referred to their darkroom procedures, I think. Whatever, Ansel's overrated.
Of course, all this information is useless to the average snapshooter, who points the camera and lets the little automatic gods inside sort it out. But, in posts to come, we'll talk about some simple things you can do using this understanding of f-stops and shutter speeds to really improve your photos. Knowing is half the battle and all that shit.
posted by Matt at 8:15 PM
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