Lesson 4Exposure Basics Part 2 - getting to know your mode dial, and other exposure controlsRemember, click on the wiki if you want to see only the lessons and not the other posts.Continuing on from last lesson, we now know why you should move beyond your cameras Auto mode and start taking control. Today we'll talk
how to take this control. Not all camera's will offer full control, but even those that don't still have ways of getting what you want, to an extent.
If you have any DLSR or mirrorless camera you will be able to have 100% control over everything, should you so choose. Most advanced P&Ss (such the Canon S110 and G15, Panasonic LX5, etc.) will also offer this level of control. However, a typical P&S (such a Canon Elph), will be quite limited.
A camera which offers full control is often referred to as having "PASM" - we'll discuss exactly what that means in a moment. Most of the time, there will be a physical dial on the camera for all options - this is called the mode dial. Sometimes, especially on low-end mirrorless or some P&Ss, these options will be menu-driven. Let's have a look at a typical mode dial, and discus what every exposure mode does, how it does it, and when you should choose one over the other. These modes could be grouped into three unique categories; let's have a look starting from the bottom:
Automatic Modes:Auto: Usually indicated by a green square, this mode is exactly what it sounds like. The camera makes every single decision for you. Some cameras will let you turn the flash off in this mode, but that's about it.
Various scene modes: There will be anywhere from none, to one, to many of these on your mode dial. These are usually indicated by a tiny icon of the scene - a flower for close-up (macro), a head for portraits, mountains for landscapes, and so on. These modes are also fully automatic, but are somewhat optimized for the chosen scene. For example, Portrait will use the largest aperture available, so as to blur the background, while Landscape will do the opposite.
Smart Auto: sometimes also called Intelligent Auto, Enhanced Auto, or something similar. This is a mashup of straight Auto and Scene Modes. In this mode, the camera will attempt to figure out what type of scene it's looking at, and then choose from the available scene modes whatever it thinks is most appropriate. This mode is usually indicated by a green square and an asterisk, or by a proprietary logo.
These 3 modes give you no control over your picture in any way. Sure, the scene mode may give you a better result than straight-up Auto, but as discussed last time, the camera is only so smart. You, being somewhat smarter (no offense
), will want to move up to the next level of modes.
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Program Modes:These are the modes which offer the best balance of control and convenience. You make the decisions, but the camera does the heavy lifting. These modes make up the P, A, and S of the PASM we discussed earlier.
Program (P): This mode is just like Auto in that the camera makes the decisions, but with one critical difference: You are able to override everything. While in Auto mode all options are blocked out, in Program mode if you're unhappy with what the camera delivered you could tell the camera what to change. Think the camera underexposed a bit? Use Exposure Compensation. Don't like the White Balance? Change it. ISO? Focusing mode? Metering mode? All within your control, if you so choose. (We'll talk separately about all these features in depth later on).
- Some cameras have something called Extended Program (or something similar). This is usually accessed via a separate button or dial (as opposed from the mode dial), and may be denoted with a P and an asterisk. What this does is very camera-dependent, but it usually lets you temporarily access the functionality from modes A and S below.
Aperture Priority(A): Most camera companies call this Aperture Priority mode, while Canon calls it Aperture Value. Hence, on a Canon it'll be denoted as AV, while everyone else will mark it as A. In this mode, you choose the aperture, while the camera chooses the appropriate shutter speed. Since this mode is the most useful and is what most people are probably best off shooting at, I'll discuss it in far more detail once we're done going through the other modes.
Shutter Priority(S): As in A mode above, Canon decided to call this differently than everyone else; on their mode dial you'll find TV, for Time Value. This mode is the exact opposite of the Aperture mode; here you set the shutter speed, while the camera chooses the appropriate aperture. This mode will be expounded upon together with A mode further down.
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Manual Modes:Manual (M): This mode is exactly what it sounds like: 100% manual. The camera does absolutely nothing for you; you dial in every single setting. There are plenty of situations where you'd use this, such as shooting stars at night, where it's too dark for the camera to figure out how to expose, of if you're shooting with any sort of supplemental lighting (such as in a studio setting). The camera has no idea that all these other light are going to go off, so it won't know to set an exposure taking them into account.
Bulb: Most cameras only let you use up to a 30 second exposure, regardless of the mode. What if you want to use something longer? That's where Bulb mode comes in. It's exactly like Manual mode, but instead of a set shutter speed, it stays open as long as you like. You'd press the shutter button once to open the shutter, then press it again when you want the exposure to end. In this mode you'd want to use a remote to trigger the camera, since you pressing the shutter in the middle of the exposure will usually result in camera shake (even on a tripod), so you'll end up with a blurry picture.
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Let's take a moment to discuss the A and S modes a bit more:
One of the first things you have to decide when composing a picture is how much of it do you want in focus. Are you shooting a landscape, and you want everything from the flowers at your feet to the distant mountains in focus? Are you shooting a portrait of your kid in the park, and want only his face in focus, while the distracting trees and people behind him should be a creamy blur? Or do you want the things in the background to be clearly distinguishable to provide context, but still want them slightly blurry to keep the focus on your kid?
In order to accomplish any of these effects you have to set your aperture correctly. With a little bit of experimentation, you will learn how your lenses render scenes. For example, in the third scenario, you don't want to be at your maximum aperture, since everything will be completely out if focus (that would be the second scenario). So you'd want to use a moderately large aperture, say f/5.6. That way the background will still be blurry, but clear enough for it to be obvious that you're in the park. For the first scenario, on the other hand, you'd want to use the smallest aperture possible, since that'll leave the most in focus. (This last sentence is somewhat oversimplified, as there are things like diffraction and hyperfocal distance to take into account. But these are very advanced topics, which will be discussed in due time.)
From these few theoretical examples, you see that focusing on using the correct aperture is a vital step. Now - as discussed in the last lesson, your choice of aperture will have a tremendous impact on your exposure. Imagine if there was a mode where all you have to do exposure-wise is choose an aperture, and the camera will choose the rest. Well, that's what Aperture Priority mode does. You tell the camera to shoot at f/4, and the camera will choose the appropriate shutter speed/ISO combination (more on ISO modes later). Lets say you take your picture, and you decide that f/4 was too much and you want more of the background in focus. All you have to do in A mode is adjust the aperture - the camera will automatically adjust the shutter speed to match.
It is very rare that if you choose the aperture and you let the camera choose the shutter speed that you will not be pleased with the results.
This is why most of the time it's best to leave your camera in this mode. Your camera doesn't know if you're shooting a landscape or a portrait. But once you tell it the vital part - the aperture - it could generally figure the rest out from there.
Shutter Priority is the polar opposite of Aperture Priority. You probably won't need to use this very often, but when you do need it it's indispensable. For example, when shooting sports, sometimes you know you need a shutter speed of 1/2000th to freeze the motion. In such a case you set your mode dial to S, your shutter speed to 1/2000, and the camera figures out the rest.
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Other exposure controlsISOYou'll notice that that as far as exposure, the mode dial only seems to cover aperture and shutter speed. Whatever happened to the third part of the triangle, ISO? Well, here's the lowdown.
All cameras have at least two ways of dealing with ISO:
Automatic: The camera chooses whichever ISO it deems best. This is sometimes good, but of course sometimes it'd be completely wrong. If you're on a tripod for example, the camera won't know this and would jack up your ISO into the stratosphere, instead of giving you a longer shutter speed.
Manual: You choose the ISO. Typically a camera will offer options from ISO 100 to ISO 6400. These go in exposure stops, so as discussed, ISO 400 will be half as sensitive as ISO 800, and therefore requires either double the shutter speed or double the aperture.
Using manual ISO along with Aperture Priority mode, we have a perfect example of why taking control of your camera is so amazing. Imagine shooting the Eiffel Tower at night, on a tripod. Left to it's own devices, the camera will probably choose a very large aperture (since it's dark and a larger aperture will let in more light), an obscenely high ISO (again, more sensitivity to light), and whatever shutter speed it calculates it needs based on these two parameters (probably something like 1/10th of a second). What do you think the picture would the picture look like? Not only will the foreground will be out of focus due to the large aperture, but everything will be covered in so much noise that the picture may not even be usable.
However, if
you take control of your camera, you could choose a small aperture, a very low ISO, and let the camera choose the shutter speed (say, 10 seconds). You won't have to worry about the fact that the shutter speed with inevitably be very long, as you know the secret that you're on a tripod.
What will happen is that everything you want will be in focus (small aperture), there will be no noise whatsoever (low ISO), and the picture will look great. Another benefit of this particular setup (small aperture + long shutter speed) is that it will introduce a number of lovely elements into the picture. The small aperture will cause points of light to appear as stars, while the long shutter speed will blur clouds, and turn car headlights into pretty streaks of light (these effects will also be discussed at length eventually). See Chaim'l's first picture
here for a great example of this scenario, including the effects I just mentioned.
Back to ISO, you'd notice that some cameras have an ISO lineup that goes like this: Lo1, Lo2, 200, 400, 800, 1600, 3200, 6400, Hi1, Hi2. What's going on here? Basically most sensors have what's called
native ISO and
extended ISO. The native settings would be the numbered ones; those are what the sensor is optimized for. The higher you go, the more noise you get. Extended ISO would be the Lo and Hi settings, and are usually the equivalent of the next higher or lower native stops. In our example, Lo1 would be the equivalent of ISO 50, Lo2 would be 100, while Hi1 and Hi2 would be 12800 and 25600, respectively. While they're equivalent to regular ISO settings regarding exposure, these settings push the boundaries of the sensor and may cause undesired effects. For example, in certain situations, Lo1 could have
more noise than ISO 800, even though officially it's only ISO 50.
Other ISO settings: Many cameras these days allow you to limit how high of an ISO it will choose in auto mode. This is very useful, and is a great thing to take advantage of. If you know that anything taken with your camera above ISO 1600 has a horrible amount of noise, you may want to limit your auto ISO to 1600 max. Don't worry that if you do that, there will be situations where you'd get blurry pictures due to the shutter getting too long, as you could always jump into manual ISO for a while if the situation warrants it.
Some cameras (generally newer SLRs) take this a step further, and let you fine-tune your auto ISO settings to an insane level. For instance, on my Nikon D600, I could set a minimum shutter speed to work along with my auto ISO. For example, If I set my minimum shutter speed to 1/500, the camera will use the lowest ISO it can and still keep me under that shutter speed. And not only will it choose from ISO presets (200, 400, etc.), it will choose the
precise ISO it needs to keep to that shutter speed - I have pictures that show ISO 633, for example. It goes even further - the longer your lens, the shorter your shutter speed has to be, all things being equal. This will be discussed at length, but for now let's just say that the longer lens magnifies blur which would usually be invisible using wider lenses. Using these ISO fine-tuning settings, I could have the camera automatically adjust my minimum shutter - and therefore, my maximum ISO - depending on what lens is mounted. If your camera offers these options, I advise you to take the time and go through them. It isn't the simplest thing to set up, but once it is it'll save you an immense amount of time while shooting.
Exposure compensation:This is one of the most important and useful features on any camera. This works in any program mode (P, A, S); some cameras allow it in other modes too. This setting tells the camera to shift every exposure up or down.
Let's examine this in more detail, and you'll see why you'd want to use this all the time. Imagine you're shooting outside on a sunny afternoon. The sun is behind you, lighting everything in front of the camera with a harsh, bright light. The camera looks at the scene, and decides on an exposure. (Remember that even if you choose the aperture for instance, it's still the camera that makes the decision on the overall exposure by choosing a shutter speed and ISO.) Now, the exposure may be "correct", but since everything is so bright, the colors are washed out. Lowering your exposure by, say, 1/3 stop should help keep the colors nice and vibrant by making everything very slightly darker.
There are two ways that you could make your camera do this. You could decide that the camera is not smart enough to lower the exposure a bit, so you switch over to Manual mode and dial in the settings yourself. You make the click, and voila!, the colors are all lovely. However, what happens half and hour later? The sun is a bit lower in the sky, so everything is a drop darker now. If you stick to manual mode, you'll now have to raise your exposure by, say, 1 stop to keep up with the falling light. Your other option is to switch back to Aperture Priority mode, where the camera could adjust itself to the changing light conditions. However, you're back to your original problem - the "correct" exposure is too bright! You'd be dancing back and forth, futzing with your exposure over and over again.
But there's a better way. The minute you notice that the colors are washed out, all you do is engage exposure compensation, and set it for -1/3 stop. What's happening is that you're telling the camera, "Hey - I'm gonna leave you to deal with the overall exposure, and change it along with the light as needed. However, whatever you do, knock it down by 1/3 of a stop." Now, you don't have to deal with changing the exposure, since the camera will adjust it when the light falls. However, now that you dialed in -1/3 exposure compensation, the colors will come out correctly too!
Exposure compensation is an incredible tool in dozens of everyday situations. Take your camera outside tomorrow and take a picture of the snow. Look at the picture and you'll notice that the snow is grey, not white. And I'm not talking about the lovely, sopping slush New York is blessed with a day after a snowfall. Look at some clean snow - and you'll see that it's grey. Why? Because the camera sees all that white snow as bright white, so it thinks it's too bright and exposes lower than it should. This is a problem with all modern cameras. How do you fix this and have the snow come out white in your pictures? Wait for it......... Exposure compensation! Set it to +1 stop and watch every picture come out beautifully. (In fact the 'Snow' scene mode (if your camera has one) does exactly this.)
Going to the zoo? Try taking a picture of a bear and have it come out properly lit. Since the bear is a small dark object surrounded by a bright foreground and background, the camera will expose for the scene and not the little bear. Dial in some positive exposure compensation, and walla, the bear looks great.
So how does it work? That really depends on the mode you're in.
In P mode, since the camera chooses both the aperture and shutter speed, so when you choose to compensate the camera will again choose which of the two (or combination thereof) to change.
In A mode, since you choose the aperture, the camera has no right to change that, so it'll use the shutter speed to compensate. So if you dial in -1 compensation, it'll double your shutter speed.
In S mode, it'd do the opposite and use the aperture to compensate.
Note that most cameras have an exposure compensation limit of +/-3 stops. You should rarely need to get even close to that limit; if your camera routinely exposes things 8 times as high or low (3 stops) as it should, you should probably get it checked out
.
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All this is well and good if you have a camera that offers all these options and controls. But what if you have a simple point and shoot? Well first of all, the main reason why you should get a better camera (after image quality) is exactly this - the ability to manipulate and control everything. That being said, there are something every camera offers, and some things that the camera could be tricked into.
Auto, Scenes, and Program modes are offered by virtually every camera. The control possible in P mode varies greatly, but most will allow you to change the ISO and White Balance settings, as well as apply exposure compensation.
As far as controlling your aperture or shutter speed, your generally our of luck. However, now is a good time to explore your scene modes and use them for things they were not really intended for
. Learn how your scene mode operate and you'll be able to trick the camera into doing stuff. For example, think about what Portrait mode does. Among others, it'll use the largest aperture available. Conversely, Landscape mode will use the smallest. That means that you now have a way to access both the largest and smallest aperture settings. Night mode will use a long shutter speed, sports a short one, etc. etc.
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In the next Exposure installment we'll dig into how the camera
sees a scene, and what makes it make the decisions it does. You'll learn all about metering, and how to use the different metering modes to your advantage.
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Lesson Summary:Automatic exposure modes:
- Auto: auto everything.
- Scene modes: Auto modes, but optimized for different preset situations.
- Smart Auto: a mashup of the tho others.
Program modes:
- Program: Automatic, but with the ability to change things as needed.
- Aperture Priority: You choose the aperture, the camera chooses the shutter speed and ISO.
- Shutter Priority: You choose the shutter speed, the camera chooses the aperture and ISO.
Manual modes:
- Manual: You choose everything, the camera does nothing.
- Bulb: Like manual, but allows unlimited shutter speeds.
ISO:
- Auto: The camera chooses the ISO setting.
- Manual: You choose the ISO setting. Some cameras allow a tremendous amount of fine-tuning.
Exposure Compensation:
- Allows the fine-tuning of the camera exposure decisions.
- Very useful to get better colors, and for tricky exposure situations.
- If you have a camera that doesn't allow this level of control, you could use some scene modes to try to replicate some of them.
- Some settings may simply not be possible.