In days of old, photographers had two choices: shoot with a camera with fixed exposure settings that was so generic it limited quality and creativity or shoot with a camera that required an advanced degree in mathematics to use but if you could master it, you had unlimited creativity and control over your photo’s exposures. That was the reality until the late 1970s.
Around that time the concept of automatic settings started showing up in the cameras and photographer’s got the ability to make one adjustment and the camera took care of the rest.
Exposure simply put is making sure the “right” amount of light hits the film for a single photo. What “right” means is up to interpretation. You might want a dark moody photo or you might want a light misty photo. But if you control the exposure, then its your decision.
Exposure is controlled though three measurements:
- How sensitive is the film to light or Sensitivity
- How long the shutter is open to let light thru or Shutter Speed
- How much light does the lens lets through or Aperture
You may know “Sensitivity” as the camera’s ISO setting. ISO stands for the International Standards Organization so its really not a camera setting, but the ISO defined the values that describe the settings. But ISO is three characters so it fits well on camera buttons.
Before we can go on, we are going to have to get into some math. Its really not complex, so don’t freak out. Remember doubling and halving.
The amount of light hitting the film or digital sensor is called an “Exposure Value” or EV. A change in EV from one whole number to another, say 1 to 2 is called a “stop”. An EV of 2 is twice as bright as an EV of 1. An EV of 3 is twice as bright as 2, 4 times as bright as 1. This concept of doubling is very important. If you go the other direction from EV 10 to EV 9, its half the light.
The EV numbers are kind of like celsius temperatures where someone decided that 0 would mean freezing. In this case EV 0 is defined as the amount of light that would be properly exposed at 1 second shutter speed with an F1.0 aperture. An F1.0 lens in theory lets 100% of the light pass through. Some typical EV numbers: A household interior is around EV 5 to 7. A Bright sunny day is EV 15. You can read a more detailed description at: http://en.wikipedia.org/wiki/Exposure_value wikipedia.
Most cameras can be adjusted in 1/3 stops or EVs of light. So you will see settings like -0.3 or 0.7 where -0.3 is 1/3 of a stop less light, or 0.7 is 2/3 of a stop more light. When you turn the dial on your camera, each click is 1/3 of a stop. You need to be aware your camera adjusts in 1/3 stops but for the balance of this tutorial we are only going to deal with whole stops to keep it simple.
Back to ISO.
Films are measured in values like 100, 200 and 800. These are the numbers that the ISO defined to standardize film measurements. The basic bright daylight film you buy in the store is ISO 100 film. Many of your digital cameras best quality setting is ISO 100. You can buy ISO 200 film which is twice as sensitive to light as ISO 100. ISO 400 is 4 times as sensitive to light as ISO 100. Your digital camera’s ISO settings mimic film, so you can set your camera to ISO 100, 200, 400, 800 and in some cases 1600 (or higher!). Of course you have those 1/3 settings, so you can set the camera to ISO 640 (and you can buy ISO 640 film too)!!!
The key thing to remember is each time you double or half your ISO number, your doubling or halving the sensitivity of your film or sensor.
The other think to keep in mind, the higher the film speed (ISO), the more grain your photo will have. An ISO 1600 speed film has golfball sized grain where and ISO 100 speed film has almost undetectable grain. With digital this grain is known as noise. This is why you don’t like the photos from your cameras when you set it to 1600. They are noisy/grainy.
Now with film, you need to tell the camera how sensitive the film is and the whole roll stays at that sensitivity. More modern cameras can read the ISO setting from the film canister so you don’t have to set it. For digital users, you can change the ISO setting from shot to shot, so you can go from bright outdoors (ISO 100) to indoors (ISO 800 or 1600) without having to change film.
Remember numbers double and half because light doubles and halves.
The next camera setting that we are going to cover is shutter speed. This is how long the shutter is open to let light through. It is measured in seconds or fractions of a second. Like film speed, a halving or doubling of the shutter speed half or doubles the light…. sort of. You are going to need to remember this chart or remember one value and do some math!!!
Lets start with the most common shutter speed to start with, which is 1/60th of a second. Your camera will show this as “60” on its displays. The reason we are starting with 1/60th is that its the minimum (slowest, longest duration) shutter speed that most people can hand hold their camera and avoid camera shake. More on that in a bit.
The standard whole stop shutter speeds for most dSLRs are:
30″ is 30 seconds which is something you might use at night shooting stars (the ” means seconds). You will notice the doubling / halving isn’t perfect. 1/8th should half to 1/16th, but its 1/15th. This is to help you remember the numbers rather than being precise with math, the same when you move from 1/60 to 1/125th of a second.
Change the shutter speed from 1/60 to 1/125 (60 and 125 on the camera display) and you have halved the light hitting the film. Go from 1/60 to 1/30 and you double the light.
A camera set to ISO 100 and 1/60 shutter speed is the same exposure as ISO 200 and 1/125th of a second. ISO 200 is twice as sensitive, but 1/125th is half the light. Its critical to understand this if your going to shoot in anything other than “P” or program mode (or the little symbol settings!)
The third number that effects things is how much light comes in through the lens. Lenses have an adjustment called “aperture” which works just like your pupils in your eyes. The brighter, the smaller the whole, the darker the wider the opening. These settings are referred to as “F-stop”. These numbers kind of break the doubling rule because we are dealing with circles, but the numbers double every other value. So your whole F-Stops are:
So changing a lens from F5.6 to F8 halves the amount of light. Going from F5.6 to F4 doubles the amount of light coming through the lens.
See we are still doubling and halving. That means if your camera is set to:
- ISO 100 1/60 F5.6
and you want to change to a faster shutter speed, you have to change one of the other two settings to keep the same exposure. So lets say you want a shutter speed of 1/125th (one stop) you would either have to change the F-stop to F4 or change the ISO to 200. If your shooting film, you really can’t adjust the ISO between shots, only between rolls, so in most cases you will balance between Shutter Speed and Aperture to set the exposure.
Our equipment gives us some practical limits. Many of our lenses do not open up any wider than F5.6, so you couldn’t in this example change to F4. Also our ISO settings are for the most part limited to 100-1600 which is only 4 stops of adjustments.
This is all the complex hard stuff. Remember doubling and halving (except f-stops which double/half every other one) and to keep the same exposure, if you adjust one up, you have to adjust one of the other two down.
Now what does all this mean and why is manual better?
Well lets look at the effects changing these numbers mean.
We have addressed ISO sensitivity already. The higher the number, the more grain or noise you get, the lower the less. Sometimes grain makes photos look better, but for the most part, we want to minimize it. But if your being creative, you might want that grainy look.
Shutter speed affects motion blur. The shorter (or higher) shutter speed, the more the image is frozen. The longer (or lower) the shutter speed the greater the chance blur caused by movement.
We call this “Motion Blur” as opposed to the lens being out of focus. Motion blur comes from two sources: The subject moving and you moving. Lets address your moving first.
A wide angle lens shows less motion than a telephoto lens does. To avoid more math, accept the fact. If your shooting at 300mm you will see much more motion in your shots than shooting at 24mm. There is a standard rule of thumb that you should have a shutter speed that is faster than 1 divided by the size of the lens. Thus if you have the standard 50mm lens on your camera, you need a 1/50th shutter speed to hand hold the shot (which is 1/60th since we are only working with whole stops!!). Your 300mm lens therefore needs 1/300th (rounded up to 1/500th).
If you’re more shaky than most, then you might need a higher shutter speed, or if your more steady, you can cheat and use slower shutter speeds. But its a good guideline. That is until digital came along. Many of our cameras sensors are smaller than 35mm film. Most Nikons are 1.5x smaller. The Consumer Canon’s are 1.6x smaller, while the EOS 1 family is 1.3x (full frame cameras aside). To keep math easy, I’m staying with 1.5x. So your 50mm lens on a Nikon D80 is effectively a 75mm lens. So to hand hold a 50mm lens on a 1.5x camera you need a shutter speed of 1/75th (which rounds up to 1/125th). That means you need to take this rule of thumb and up it one shutter speed if you want to eliminate blur from your shaking!!!!
Your motion blur is almost always unwelcome and you need to keep this minimum shutter speed formula in mind. Unless you have a Vibration Reduction / Image Stabilization lens, you should put your camera on a tripod if you have to have a slower shutter speed. These VR/IS lenses generally let you hand hold exposures 2-4 stops slower than non-VR lenses. So if you are of average shakiness, and you need a 1/60th to hold a 50mm lens, then you can typically hand-hold 1/8th to 1/15th of a second with a VR/IS lens. Keep in mind though, VR/IS lenses are for your movement. They don’t do squat for your subject’s movement.
Subject movement can be desirable or not. Lets look at a couple of examples. Taking a photo of a helicopter at a high shutter speed will freeze the rotor blades and the helicopter will look odd just sitting there in the sky. In this case, you want a lower shutter speed to allow the rotors to blur, but not so low that the helicopter itself blurs and the photo will look much better.
Shooting a car racing around a track with a high shutter speed makes the car look like its just sitting still, where as a slower shutter speed will let the wheels turn during the exposure giving some sense of life and movement to the photo.
Shooting sports, people think you want to freeze action, but that’s not always the case. Sometimes some blur in the hands and feet convey motion to the viewer and can make for a more dramatic photo. But a lot of times you want to capture your child playing and you want a high shutter speed to do this.
So how much movement freezing you want is up to you and if you control the shutter speed you can make those decisions.
The lens opening controls how much of the photo is in focus. With an aperture/f-stop of say F2.0, very little of the photo will be in focus, maybe only a few inches. This is called “Depth of Field”. Sometimes a blurred background while the foreground is in focus is desirable. You need a lens that can open wide, say F2.8 to do this. Sometimes you want a lot in focus. You need a high Fstop of say F11 to get that effect.
Keep in mind the closer you are to the subject the less will be in focus, the further away the more depth will be in focus. Shooting a closeup portrait at F11 will still have a blurred background where a F2.0 fstop may only have the eyes in focus.
Shooting manual gives you control over motion, depth of focus and grain and how you mix those determines the look of the photo.
But wait, thats not all. If you call now, we will also include….
You’re saying “something is still missing” and you’re right. You get the doubling and halving and the effects they cause, but what does it all mean?
If you look at any given scene you shoot, there will likely be some dark things, some bright things and some things somewhere in the middle. If you were to look at everything in the photo and average dark, light and in between you would find that in most cases it averages out to the middle values.
Our camera’s have meters that look at the scene and determine what this average middle value (and since we don’t care about color here, just shades of grey), the camera wants to declare a photo properly exposed when there is enough light hitting the film/sensor will cause everything in the scene to average to middle gray.
In most cases this works and this is the basis of your camera’s automatic settings. Lets quickly look at the settings and what they do:
P or Program:
This mode, the camera figures out what ISO your camera is set to, then tries to adjust the shutter speed and aperture for you to the safest settings. Its going to make sure you have enough shutter speed to hand hold the lens and then if there is enough light, work to get an average depth of field to get enough in focus. If its really bright, it will push the shutter speed up, if its dark, it will try to open up the lens fully before having to cheat on the shutter speed.
You end up with very average photos in P mode. I never use this mode.
A or Aperture Preferred (Av in Canon terms):
This was the first automatic mode to show up on cameras. You set the lens to how much light you want to let in, the camera then calculates the right shutter speed based on the ISO setting. You only have to control one thing. (Note, I shoot in this mode for my general photography). You have some control, but the camera is still trying to get to that average middle gray and you might be forced into some shutter settings you don’t want.
S or Shutter Preferred (Tv or Time Value in Canon terms):
In this mode, you pick the shutter speed, the camera sets the lens opening. You can concentrate on how much movement you want in the photo or how frozen things need to be and the camera makes the rest of the adjustments. I rarely use this mode. The one time I find this useful is if I’m trying to use flash outdoors and I need to guarentee the shutter is open long enough for the flash to fire.
Then there is the M mode or Manual.
In Manual YOU are responsible for both the Shutter Speed and Aperture settings (and the ISO setting for that matter). You’re saying “Why would I ever want to do that since I can control depth of field and motion using the automatic modes?” That’s a good question and there are two main answers for that.
1. The camera meter is frequently fooled. A really bright spot will make the camera think its brighter than it really is, causing the photo to be too dark. Or your shooting someone in a room with dark paneling on the wall. The camera will see that dark wood and make the photo too light.
Since our scenes are not always “middle gray” you need to be able to recognize these situations and be able to adjust for it. A classic problem is your kids are playing in the shade of a tree and you want to shoot that, but there is a lot of bright grass in the background and it tricks the camera and you get a dark photo.
Since You have the ability to look through the view finder and see what is really there, you have the ability to fix this problem by adjusting the settings.
2. You might want a photo to be brighter or darker than the camera wants for creative reasons. You want one of those “High Key” all white portraits of your kids? If you leave it up to your camera, you will get a nice gray photo. By shooting in manual, you can adjust the camera to what you want to accomplish and not take what the camera thinks you want.
There are more than these two reasons but those two are the main ones and the rest can be classifed into either of those.
Some other examples of where Manual is better:
- Studio Photography — your camera meter can’t measure studio strobes and you generally have to have a special hand held meter to get the light settings and then you dial the camera to the right settings.
- Shooting in a gym — the light falling on the players is fairly even in most cases, but dark bleachers, white walls, dark away jersey and white home jerseys will almost guarantee that you won’t have a middle gray photo, so meter off of something mid-toned and set your camera manually and shoot the game without having to worry about if your camera has a bunch of away jerseys against dark bleachers throwing the camera off.
Finally shooting in manual makes you have to think about these three settings and once you understand them and can shoot successfully in manual mode, then you will be able to move on to dealing with flashes and such.
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