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photography :: what the f/stop?

with 2 comments

if you’re like me, you’ve put off learning the basics of manual photography way too long. all those numbers and decimal points: they make my brain hurt and my heart race. my eyes go blurry with each page, which often read like an eternity. automatic is fine by me, thanks—until now. it’s time. i can handle it. so can you. here’s what i’m starting with:

time of day: early morning and late afternoon produce long shadows, which make pictures more effective. but this doesnt mean you shouldn’t go out shooting at other times.

ISO: the sensitivity of the film. the more sensitive, the less light it needs; the less sensitive, the longer you need to keep the shutter open—not good for photographing things that move. my grandpa once told me about 800 speed film; it saved me from needing a tripod. the least sensitive i’ve seen, the one needing the most time with the lens open, is 100.

shutter speed: the shutter speed is one of the two basic exposure settings on your camera, the other being the lens opening which i get to next. shutter speed determines the amount of time you allow light through the opening of the shutter—how long you expose the film to light. remember your ISO number: the higher that number is, the less light you’ll need to produce a photo, which means you can snap away at faster shutter speeds. some cameras can go as fast as 1/8000 second (the standard unit for measuring shutter speed) and some can keep the shutter open for 30 seconds, a long time in the photo world. with the automatic setting, your camera will choose the best speed to try and capture a still image, read: not blurry. but what if you want something blurred? what if you’re off at the races and think a trail behind a horse would look pretty cool. the shutter speed will help you with this effect.

here’s the math: as you decrease the shutter time, making the snap quicker, you cut the amount of light hitting the film in half. as you increase the shutter time, holding it open longer, you double the amount of light hitting the film. this doubling and halfing will, i’m sure, mean something to me one day.

f/stop: this is the term used to indicate the opening of the lens. its other names, which are a bit more descriptive, are lens aperture and lens diaphragm. this determines the amount of light allowed to pass through the lens.

from largest opening to smallest, here are the most common f/stops: f/2, f/2.8, f/4, f/5.6, f/8, f/11, and f/16. notice that the numbers on this one feel a bit counter-intuitive: when you increase the lens opening the number paired with the ‘f’ decreases and vice versa.

here’s the math on this one: as you let more light in by decreasing the f/stop number you double the amount of light hitting the film. as you slow the light coming in by increasing the number you increase the amount of light by half compared to what it was before.

reason to care: so far, the most intriguing reason to learn this stuff is called “depth of field”. depth of field is a way of saying what in your photo, from the foreground to the background, is in (sharp) focus. if you want a sharp foreground and a fuzzy background, set the f/stop to the largest opening—or the lowest number on the number line. to have the entire photo in focus, use a small lens opening, the smallest f/stop—or the highest number on the number line. and everywhere in between. see, fun. i’m sure the shutter speed plays a role in making sure you don’t overexpose or underexpose your work—go outside and figure it out.


Written by Gabrielle

November 22, 2010 at 10:01 am

Posted in how-to, photography

Tagged with ,

2 Responses

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  1. It sounds like a huge undertaking, but it’s really not that bad once you start working with it 🙂 I prefer to think of it as the trinity of exposure – ISO, f stop, and shutter speed. Pick the point for the effect you want and adjust the others for a good exposure.

    In other words, if I want a shallow depth of field, bump the ISO and SS until it works.

    (also note that high ISO adds a nasty grain or digital noise.)

    Good luck!


    November 22, 2010 at 12:51 pm

    • hey…thanks for weighing in. i’m looking forward the learning curve.


      November 22, 2010 at 3:01 pm

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