Since it is the easiest to understand, let us begin with "Shutter Speed". Although the electronic controls on modern cameras have the ability to make infinite changes in shutter speed in general the shutter speeds are indexed where each setting is either � the speed of the preceding index or twice as fast. By example, a typical shutter speed dial would be indexed as:

1000 � 500 � 250 � 125 � 60 � 30 � 8 � 4 � 2 � 1 � M

Each of those numbers is actually the numerator of a fraction, thus 1000 is really 1/1000 of a second.

Notice that from any point if you move up one click it doubles the number, which cuts the actual time in half. By example moving up from 125 to 250 the exposure changes from 1/125 of a second to 1/250 of a second. That means the exposure time is cut in half and only half as much light will hit the film or digital sensor. On the other hand, if you move down from 125 to 60 the time changes from 1/125 of a second to 1/60 of a second and it allows twice as much light to hit the film or digital sensor.

On the bottom end of the scale you see the letter M. That indicates Manual Exposure, and when your timer is set to M the shutter will remain open as long as you hold the shutter release button down. When working in extremely dim light we attach an external shutter release that has a locking mechanism and we can make the exposure time however long we need it. (I have shot pictures that required a 6 or 8hr exposure).

THE APERTURE is a movable mechanical device inside your lens that can increase or decrease the size of the opening through which the light passes and the setting increments are called "f-stops".

Technically the f-stop number is an index that means the actual diameter of the opening is equal to the focal length of the lens divided by the index number, but you need not worry about doing all that math, just memorize the f-stop scale.

F-STOP SCALE 16 � 11 � 8 � 5.6 � 4 � 2.8 - 1.6

Remember that the F-stop guide is dividing the focal length by the index number so the higher the number the smaller the actual lens opening. Now, here again, by moving the selector one f-stop you are either doubling or halving the amount of light entering the film plane or digital sensor.

The question then becomes , Why would we want to make these changes?

With the camera set in the normal mode it is assuming you are shooting a stationary subject, or perhaps people who are simply walking and the camera will select a shutter speed in the order of 1/125. But what if you are shooting sports shots where the subject is running, or perhaps a racing car. At 1/125 the subject is moving too fast and you get blurry pictures.

Let us assume in the normal mode the camera says the correct exposure is 1/125 @ f-11 but you are shooting a race car and want to use 1/1000 to get stop action. You click your shutter speed up to 1/1000 and note that it was 3 clicks (125-250 250-500 and 500 -1,000). Since you changed the shutter speed three clicks you must now open the lens 3 f-stops so you change from f-11 to f-4 and you will get the same exposure.

Now notice that the ISO speeds also increase in increments that double, i.e. iso 100, 200, 400, 800, 1600 @ 3200 thus each increase in iso speed is also equal to one f-stop.

Later I will post how to use the aperture and shutter speed to control depth of field.

Awesome! Thanks Lazypup!!

Tropicalfreak

Nice work by lazypup!

One other way to think of it is to equate what the camera sensor sees to how the human eye sees:

Think of shutter speed as how quickly you blink your eyelid. A quick blink is like a fast shutter speed like 1/1000 of a second. With a quick blink you hardly expose your retina to the image you are looking at. A longer gaze where you stare at an object would equate to a slower shutter speed like 1/30th of a second.

Think of aperture as being related to the size of the pupil in your eye. A wide open or dilated pupil is like a low f-stop number (a more open lens aperture), it lets a lot of light through to the sensor. A pinpoint-sized or very small pupil is like a high f-stop number (small lens aperture opening), it lets little light through to the eye's retina or to the camera's sensor.

In the daytime in bright sun, your pupil will naturally decrease in diameter/size. It's trying to not overexpose your retina to bright sunlight, it's like using f-stop settings toward one end of the scale, f/8 to f/16.

At night when light is limited, your pupil will open up wide to let light in, like a camera's f-stop settings in the f/5.6 to f/1.4 range.

Think of ISO as how good your night vision is, or how well your eye or the camera's sensor sees at night. A high ISO number means you have excellent night vision capability. You might not always use the high number, but you have the capability. So a camera with a sensor that goes from ISO 100-1600 will be fine in bright light and at dusk, but in darker situations (indoor or theater photography) you'll wish your sensor was from ISO 100-6400.

In general, the higher the ISO setting, the more artifacts or "digital noise" can be introduced into the picture. So you want to keep the ISO towards a lower number when able. Just because you can see at night, it doesn't mean the picture will be perfectly clear. One other thing, it is relative: ISO 1600 on a camera with a 100-1600 range will be grainier or noisier than 1600 on a camera with a 100-6400 range. The closer you get to the highest ISO setting your camera offers the more likelier you are to get noise. It's not a hard rule, just a guideline.

You can still use a camera's flash to illuminate what you are photographing, much like a person would use a flashlight to see better at night. But a sensor with a high ISO rating allows flashless photography in low-light situations. Plus, a camera's flash can only illuminate so far out in front of the camera. At an indoor graduation ceremony you'll want to be in the front row to effectively use a flash. With a high-ISO camera you could be in the rear of the auditorium and still get nice shots with no flash.

These three things; shutter speed, aperture or f/stop, and ISO, can be thought of as sort of making up the three corners of photography. There's fluidity between the three, shooting one of your camera's manual or priority modes allows you to vary things as needed for what you are shooting.

Like lazypup wrote, shooting outdoor sports you'd want a fast shutter speed (a quick blink of the eye) so the fast moving athletes won't be blurred. A fast shutter speed limits the amount of light that gets to the sensor. So you can increase the amount of light that gets to the sensor by using a lower number aperture setting like f/4 or f/2.8, and an ISO setting like like ISO 200 or 400. In bright sun you could be ISO 200 for example, if there are clouds, the 400. These are just theoretical numbers mind you, not real-world specifics.

If I'm in bright sun shooting outdoor scenery for vacation photos, I can have a low ISO number to maximize photo quality like ISO 100, a smaller aperture opening (smaller opening means higher numbered setting) like f/14 to maximize depth of field so everything in the photo, from foreground to background, is in focus. Then whatever shutter speed is required to make the desired ISO and f/stop work.

Shooting indoor theater I want flashless photography. There is some motion on stage, maybe a little dance here and there, so I can use a somewhat slower shutter speed like 1/200th of a second to keep the moving actors from blurring, a sort of medium blink of the eye. I still need more light though, so I'll open up the eye's pupil with a wider aperture setting like f/2.8, and I'll give the sensor better "night vision" by increasing the ISO to a higher number like 800 or 1200.

If I'm taking photos of a non-moving sleeping baby in a quiet room, blur really isn't an issue, so I can use a slower shutter speed of 1/60th of a second to let light in. I can use a medium-ish ISO like 400, and I can open up the aperture with f/5.6.

All of the above are sort of wags of numbers to try to convey the idea of how the three things can be adjusted to compensate for what you are trying to shoot.

The thing you'll find is that based on what you are shooting, one of the three things will be prioritized. Fast moving athletes might lead you to prioritize shutter speed to control blur. I might shoot in "S" mode to prioritize shutter.

Shooting your child on stage in a school play might lead you to open the aperture wide open to maximize light to the camera's sensor. I might shoot in "A" mode to prioritize aperture.

Lazypup said he'd write about depth of field, that can be an important criteria that leads to using a certain f-stop or aperture setting.

So lots of variable. But you only learn by shooting, analyzing your shots, and trying different settings. The "delete" button is one of the beauties of digital photography.

just gotta say, I'm looking into getting a DSLR camera, and really appreciate these simple to understand instructions and have printed them out

The best thing any beginning photographer can do is buy themselves a book about the basics. Shutter speed, aperture and ISO are just the beginning. Although I dislike the title, "The Complete Idiot's Guide to Photography" is a great book to help master the basics.

Hi Jean,

If you are thinking of getting a DSLR, the new Nikon D3200 entry level camera packs a lot of "bang for the buck". It performs competitively some very expensive cameras. They even have a red version of it, if you want something a bit less formal than solid black. I got the black one, taking advantage of the $150 off bundled price of the Nikon 55-300mm f/4.5-5.6G ED VR AF-S DX Nikkor zoom lens. That lens complements the kit lens (18-55mm f/3.5-5.6 AF-S DX VR NIKKOR Zoom) very nicely.

The kit lens is very versatile, and focuses from infinity to 11 inches throughout its zoom range. You can get some good closeups with it. Both the kit lens and the telephoto have VR (vibration reduction), which is Nikon's name for image stabilization. I have gotten some decent shots of butterflies handholding the stabilized telephoto at its maximum telephoto setting of 300mm. That kind of amazed me, because I thought I would have to use a tripod at that much telephoto.

If you are thinking of getting the Nikon D5100 instead, be aware that it is due for an upgrade to the D5200 in the next few months, at which time you might prefer to get it, or take advantage of probable price breaks for the D5100.

ZM
(not associated with any product or vendor mentioned or linked)

ZM...awesome..thanks so much. I probably should have clarified, I want the camera to shoot video.

The Nikon D3200 can shoot video just fine.

This little chart was found on pinterest. Easy cheat sheet for quick reference!!! (clickable)

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Found on pinterest! A quick reference guide sheet-thought it pretty cool!