Many people taking photos today only use camera point&shoot automation without any concern about what the automation is doing, and without any worry about what could be done better. The light meter can measure the light, however automation cannot recognize the scene nor any special photographic needs. Automation can only try to make the exposure come out "not too dark and not too bright" (when that is possible). That is a picture, but to actually "create the picture", the situation often requires a human brain and a quick thought about what best to do about it. So only the easy normal pictures have much chance to come out right, but some situations do require more ... a bit of human thought. So while some people are only interested in point&shoot automation, others are more interested in photography, and enjoy doing it better to actually create the picture.
Learning Exposure is the beginning skill that you need to acquire about real photography using an adjustable camera instead of point&shoot with complete automation and taking what you get. If you don't understand about choosing camera settings yet, you may want to look into it. Camera settings have much capability for even the difficult pictures, which automation can not handle (any difficult situations are generally impossible for the automation). Automation is handy, since we don't have to know anything or to think about it (and we likely won't even realize or care what the settings used were), but then the only result is just whatever the automation does, and we ourselves don't get credit for doing much to create the picture. The issue is that automation has no brain, and needs human help to recognize the scene situation to choose better choices for a specific scene.
"But Exposure" is NOT just about how dark or bright the picture is. The full meaning of Exposure is about using the right camera settings to get the best picture, like by freezing the subject motion, or sometimes maybe intentionally blurring the motion (a waterfall maybe). Or by stopping down aperture to increase the Depth of Field. Depth of Field (DoF) is the size of the range of the zone of acceptable sharpness around the focused point. Or maybe shooting with lens wide open to intentionally blur away an objectionable background. How do we make an acceptable portrait under a shade tree with a bright sun background, or if indoors with a bright window behind the subject? Both subjects will be too dark unless we intervene with better settings. Is the scene like a black cat in a coal mine, or a polar bear on the snow? (or your dog on snow?) Without your intervention, both will be metered to come out gray (neither correct as gray). That gray situation could instead just be a group of black tuxedos or a portrait in a white wedding dress. The camera automation only sees some light, without a clue about what it or the situation is. But your brain does immediately recognize the situation (if you bother to actually look at it), so with a little experience, your help generally only requires a glance and a brief thought. Situations vary, and need different techniques. That is photography, which is a lot more than just a cell phone. There is more to be considered than just locating the shutter button. It is very helpful if your brain actually looks and recognizes the situation. Then skill is often about just remembering past situations.
There are many creative choices possible in photography, which do require an adjustable camera, and knowing a few basics, and most of all, a couple of seconds of thought about the situation and what we are to do about it. But it's all easy, and is the first thing photographers must learn. And it's fun getting it right, and soon becomes our automatic procedure, so that we usually just already know what it needs when we first walk up to the scene. The brain is the photographers best tool, and knowing a few basics is a huge help too. It is easy to see, it is all right there in front of you. You just have to look, and think a second about what you are doing.
Choosing WHAT to point the camera at is a different discussion, but any photo scene allows a wide choice of possible Equivalent Exposure combinations, all "correct" with regard to exposure (even our cell phone camera must select one), but generally, only one is "best" (and several may be quite "wrong" for the situation). The big advantage of using our human brain is that it can immediately recognize the subject and the situation, and can choose the best choice for this particular picture (and automation simply cannot). Good Exposure does NOT just mean not too dark, and not too bright. It also means choosing the best available exposure combination for the scene situation. If we consciously think a second about what we're doing when we actually LOOK at the scene, our brain learns to likely "just know" immediately what it needs. Past experience (seen it before) is a big part of skill. Unless of course, you just can't be bothered to think about what you're doing. 😊
Shown here is an example of just three rows from the EV Chart (Exposure Value, which is a combined value of f/stop and shutter speed) showing sample values . The chart EV is sort of a brightness level of the light, as modified by our cameras ISO setting. EV 15 is a normal bright direct sunlight level (at ISO 100). What the chart shows is that there are several Equivalent setting choices all for the same exposure. For example one exposure combination for this EV 15 is f/2.8 at 1/4000 second. (1/4000 freezes fast motion, but f/2.8 is not much depth of field). Or f/22 at 1/60 (much depth of field, but won't freeze fast motion. Or maybe 1/500 at f/8 is generally the best suited overall compromise). We can choose what is best suited this time, and taking a few test pictures to explore this sometime will be a very valuable lesson.
The Idea of it, Why and How
: I am trying to be brief while not leaving out much, which is of course doomed, but this is my try. I do include a couple of points (in Italics) that might be considered a bit advanced (about relationship of EV and ISO, and a mention of Depth of Field CoC), which is too much for first day, but they do seem important for actually understanding anything. If you're a little techie, you'll like it and there are other pages here too, but if not, you can ignore it for now.
All entries on any one entire row of the EV chart are Equivalent Exposures. Equivalent means that any and all of them are a "correct" exposure (for the row's matching light level), but we're looking for the one best combination for our specific situation. The standard EV chart is for any ISO, specifically it is for your current ISO, including Auto ISO. A different ISO will match a different EV number on a different row. The EV number (Exposure Value) is the camera settings (f/stop and shutter speed) for exposure of the current light level at the current ISO.
The light meter will suggest some f/stop and shutter speed for the current scene. But then from those settings, we know that a wider aperture (a smaller f/stop number, towards f/2.8 or less) is less Depth of Field but is more light, and the larger f/stop number (toward f/16 or more) is more Depth of Field but less light. The fastest shutter speed (towards 1/4000) is less light, but it freezes the fastest action. The slowest shutter (like 1/30, or even 10 seconds) will not stop fast motion, but it is more light. So we choose a better combination based on the situation's need for Depth of Field sharpness, or about motion to be frozen, and in particular, that using a wider aperture can compensate for the lesser light of a faster shutter speed, and vice versa (Equivalent Exposures). So our goal is to weigh the balance of factors to choose the best combination for our scene. This is generally much easier than might be assumed (it is virtually automatic with a bit of experience). But the automation can only see some light, and cannot recognize what the scene is or needs. The cat in the coal mine and the polar bear on the snow both come out mid-tone gray. Humans know that isn't going to come out right.
No worry, in practice, you don't have to calculate anything. There are Depth of Field calculators, but just knowing a couple of basics will let your intuition tell you all you need to know every time. All you have to do is to learn to actually look at the situation, and recognize its needs.
First, a definition of Depth of Field: Every picture (meaning every camera's settings result) have some degree of Depth of Field. The lens of course has the best sharpness at the one exact focused distance, and it gets less sharp at distances further from focus (distances both in front of and behind the focused distance), which eventually gets far enough out of focus to call it blurred (just beyond those distances, not at focus).
The blue object represents the camera lens, and the dark black vertical line at far right is the camera sensor where the scene is focused.
A “point” is the theoretical zero size of a hypothetical point when perfectly focused.
The Blue line is the actual focus point at S1.
The Red line is the out of focus distance of a “point” at S2.
C is the blur circle of the zero size point at S2.
c is the reproduced CoC size on the sensor.
CoC is NOT the size of any scene object, it is about every computed out of focus hypothetical spot of original zero size.
DOF computes the near and far distance limits where c does not exceed the maximum permissible CoC specified for the sensor size, which is judged to be Not perceptible by the eye after a standard 8×10 inch enlargement at the standard viewing distance of 25 cm (10 inches).
More detail at Wikipedia.
A bit of Math talk, maybe out of place at a beginning level, but an explanation of Depth of Field should answer future questions. There is a number called CoC (Circle of Confusion, capital C in the diagram, which is the calculated diameter of the blur of a hypothetical infinitesimal size point at a specific distance from point of focus). This tells how much blur is at that distance.
Its image is projected onto the sensor as the size marked lower case c. The maximum acceptable size of c on the sensor is the number we discuss as CoC. Not what size it is, but the size of its maximum acceptable limit to be called sharp.
The acceptable CoC limit (which is the one that we call CoC, which then specifically means the value that is the limit of acceptable blur). So what Depth of Field calculators do is to compute both the near distance and the far distance (distance on both sides of the lens) where this blur diameter reaches the CoC limit. The actual size is determined by the lens focal length and aperture. The CoC limit is determined on the sensor size (due to its need for considerable enlargement to a viewing size of 8×10 inches, which enlarges blur too). CoC varies inversely with sensor size, smaller sensors require greater viewing enlargement, but they use shorter lenses, which somewhat balances out (not exactly, camera settings like aperture and focus distance also have effect).
This CoC limit, when exceeded, determines the distance point where Sharp Enough becomes NOT Sharp Enough. This limit determines the near and far distance extents of the zone of adequate sharpness (either side of focus) called Depth of Field. The math uses CoC as a hard limit at an exact distance from focus, but actually, sharpness falls off very gradually across that limit. Then Depth of Field is considered the zone of the still acceptable sharpness around that focused point. But if the CoC limit is 0.03 mm, then 0.03 is considered sharp, and 0.0300001 is not. But blur is a vague thing, and Depth of Field at CoC is an adequate guide — normally we are just guessing our distances anyway.
Depth of Field is Not a difficult subject, but it really is more than is appropriate for a First Day introduction. You will get to it again pretty soon after you begin, and this explanation is intended to help then. Providing adequate Depth of Field in your pictures will become important.
Anyway, let's say our scene has important objects at about 10 feet and at 30 feet that we want to be sharp. Making up an example now (for a 1.5x crop factor camera with a 50 mm lens), maybe the light meter suggests f/5.6 at 1/1000 second (which numbers are EV 15 for any ISO we are using, since a different ISO would change the lens settings we are using). We know that focusing at a distance a bit into the DOF zone (some say 1/3 of the way in, which may be common, but it varies) provides a zone of more sharpness on either side of the focus point. The Depth of Field calculator says a focus at 15 feet and 50 mm at f/5.6 (with that camera) has the DOF zone from about 12.4 to 19 feet. That won't handle our situation of 10 and 30 feet objects. And we don't see any need for 1/1000 second speed to stop motion in this scene. And it so happens that focus at 15 feet at f/16 1/125 second is Depth of Field of 9.5 to 35 feet, so that is an acceptable choice.
In practice, we don't know those numbers out when out at the scene, but we do see the scene, and our experience may know this case does not need 1/1000 second but does need more Depth of Field if we can provide it. And we can. The 10 and 30 foot points still won't be as sharp as the point of focus at 15 feet, but our help makes the difference be very slight, probably not noticeable. This example is only intended as giving a first clue about how lens Depth of Field works. A picture can only be focused at one point, and Depth of Field is the range of the sharpness zone considered acceptable around the point of focus. Our eyes and brain have considerable control of that zone.
Don't misunderstand, in practice, we almost never look at an EV Chart. And of course, we really don't know accurate distances to objects in our scene anyway. And we don't have a Depth of Field calculator with us in the field. The light meter gives us some shutter speed and f/stop for the ISO we set, and we don't know the actual EV number unless we look into it (there is a little formula for EV). But there can still be a good plan.
But what we do know is that we can see that our scene objects (at about 10 and 30 feet) has an extended distance range needing more Depth of Field, so we stop down f/stop (to a larger f/stop number) to give it "more". We usually don't know any numbers, but are thinking in units of needing "more", so we give it "more". And we focus a bit into that zone to provide more sharpness on either side of focus (instead of wasting the sharpness in front of the focus point, where there is nothing important). Or in another situation, we might see that the scene has some motion needing faster shutter speed to freeze it, which the light meter cannot recognize, but our brain can, so we give it "more" with shutter speed. If it appears to be an exception situation, we give it all we've got. We don't know exact numbers, but a little experience will make a big difference (having seen similar situations before). And the EV Chart has shown us that there are always several possible equivalent exposure choices we can choose. And adjusting shutter speed and f/stop oppositely but equally, is still an Equivalent Exposure (as the chart shows). Your brain is the best photography tool you have. Use your head, and don't waste it, it's very useful.
So in practice, we see that our scene has objects both fairly close and fairly far, so we know more Depth of Field is important. And we do know if there is any motion in our scene (including our ability to hold the camera still with a slow shutter speed), then shutter speed would be important too. And we do know that stopping down the aperture will increase Depth of Field, and if we realize we need some of that, we take our best shot at providing it. But if there were also some motion in the scene, making shutter speed would be a factor then too. You brain can understand all of this, and if necessary, we compromise to do what we can, based on what seems most important. And it generally works out rather well.
However, the proper exposure of the light (maybe bright, or maybe dim) can also impose restrictions on what is possible. It may not leave range for the setting to what this situation needs. If too dim and shutter speed is too slow to handhold, we can use a tripod. Or higher ISO can allow stopping down f/stop or to use a faster shutter speed. But an ISO excessively high can worsen the picture. But stopping down f/stop can increase Depth of Field. The camera knows how to implement our setting choices, but the meter is just a dumb chip unable to recognize the scene situation to know which settings are best. So the big point here is that our brain is the very best tool in photography. It looks and sees and knows many things at a glance, and it can help the camera, if we choose to think about what we are doing. Yes, it might be a puzzle at times, and it might sometimes require a compromise, but it's not so difficult. We do see everything right in front of us (if we just bother to look). This is the fun in photography for many of us, to create the photo ourselves, to be the way we want it. Experiment a bit, and actually look at what you see, which is the first step of photography and understanding. What you learn will help your photography, to be enjoyed as a life-long hobby. But it will require an adjustable camera.
The light meter only sees a blob of light, which it can measure accurately, but cannot recognize the situation to know what it is or actually needs instead. So this automation can choose the actual exposure of many "average" scene contents, but only our human brain can choose how those camera settings should be first modified for the more difficult special cases when the automation fails.
The light meter first meters the scene, and then we might change some of the three exposure factors to be better for some specific needed reason. If using camera mode A, we change aperture. Camera mode S, change shutter speed. If using Auto ISO, you might need to set a specific ISO. We looked at the scene and know what it needs. The meter is certainly a big help, but do give a thought to what you're doing before you press the shutter button. Simply just looking is a real big deal. This is easy, and soon you might not always even realize you're doing it automatically. Like checking your car's side mirror before changing lanes. You simply just glance at it, and the extra little bit of thought can dramatically improve the results of the situation, far better than not glancing first. Try this a few times, and it becomes easy and automatic.
Another simple example of this learning concept in difficult situations: The case of a picture of a person indoors, but with a bright window behind them showing the sunny outside. Or a subject in the shade of a tree but with a bright sunny background beyond them is the same thing. The light meter sees that sunshine, and these are relatively impossible scenes for point&shoot. Automation cannot recognize this situation, and will be heavily influenced by all the bright outdoors light, but the photographer is more interested in the relatively dimly lighted subject, and needs to know how to compensate the picture. There are some easy ways, but the first important action is to recognize the scene and its special requirements. Just stop a second to look, and think, and actually see it. You will need an adjustable camera better than the smart cell phone.
Some choices for a too bright background, solved by looking and thinking a second:
- If possible, simply move around so that there is no bright window behind the main subject, because it is a huge obstacle to the automation. Otherwise, the subject will be far too dark. Instead of just wondering why the poor picture, you will be way ahead by just simply recognizing the situation.
- If you can't move to avoid the window, a quickie fix is to simply aim the camera down toward the subject's feet, enough that the bright background is Not included in the view finder. Half press the shutter button to lock in that exposure without the window, and then still holding half press retaining that exposure, re-aim up on the subject and the Full click the picture (but cell phones have no half press feature). Due to the window, the light in the same room should be about the same down there. We might debate if that metering accuracy of the feet is exactly the same as the face, but it should be close enough, and is a quick method, and it normally works great. Just try it. It will solve the problem.
- Or assuming an adjustable camera, examine the first too-bright picture result on the camera's rear LCD, and compensate the exposure for less light and try again. And repeat if necessary until you get a good picture. Compensate meaning, if in a camera automated mode (like camera Mode A), there is a compensation button, like -1 EV is half the exposure, and -2 EV is 1/4 the exposure. If a manual camera, stop down the aperture or increase the shutter speed or reduce the ISO (less exposure). A little experience will make the next time easy.
- Any picture only has one exposure for the entire frame area, so these corrections will then overexpose the bright outside scene (perhaps to be near white), but if that outdoor scene is also important and desired, then instead half press (and hold it at half press) likely sets a camera exposure correct for the window's outside scene (which leaves the indoor subject dark), but (in advance preparation) add a TTL flash for the indoor subject, which will trigger at Full press. Bounce flash is normally very good indoors, except this time, a bounce power level will have trouble at the outside sunlight exposure settings. There may be some minor ifs and buts then, and if so, you can see what it needs. But likely this will make both scenes correct.
Thinking about what you are trying to do is important. If you can't be bothered with it, that's one thing, but if interested in improving your photography, and looking to make it be an enjoyable hobby, then when you become aware that you're supposed to take a second to actually LOOK at the scene first, you will have a pretty good idea about the situation when you first walk up to it. When you can recognize it (and all you have to do is to just actually look at it), you will know what it needs. Then you can get a great picture where the automated camera would simply fail. Look for the basic things to think about, like:
Before you click the shutter, you should have decided what modifications to the metered settings are needed. The best choices usually become obvious when you actually look at the scene situation. In most cases, this is not at all difficult, and soon we will be able to "just know" at a glance when we walk up what will be better, or necessary. A little experience does help (experience is remembering what you have seen before). It does require a bit of thought about what you are doing.
- Any larger scene areas of dark or bright that might adversely affect overall exposure? Even if not behind the main subject. That will require choices.
- Any important objects too near or far from the focused point for adequate Depth of Field? (DoF is the range of sharpness, which is adjusted with aperture and focal length). Stopping down (towards f/16) will help, but will need a slower shutter speed (or higher ISO) to compensate exposure.
- Any fast motion needing freezing with a faster shutter speed? Any motion (like a waterfall) you want to emphasize by blurring with a slower shutter speed? If the shutter speed is slower than you can hold steady, it needs a tripod. If the shutter speed is faster than your available settings, higher ISO will help.
- Any problem background details that ought to be avoided? (either blur the background, generally with a wide open short lens or maybe a longer lens, or maybe better, just move a little sideways to exclude that bad part of the background from view). A longer lens or zoom will reduce the width seen. Is there a a better choice of distance or zoom, or of camera height or angle?
- Image Composition is an art itself, and is another subject, but always consider framing the subject tighter (closer) if that omits areas of wasted surrounding blank space or objectionable surrounding features (and tighter framing also enlarges your subject in the frame). However if a wider view shows more that should be seen, great, that wide view is clearly important as a good thing. But if you are trying to show detail, then are you close enough? But are you too close to include all you want to show? Too much clutter, more than you want to show and distracting from the subject? Pause to think about what the viewfinder is showing you. Is it what you want to show? Perhaps the situation needs both a near and a far view? Maybe think about what you want to show, instead of just "there's something else to click on".
- Think to check in the viewfinder that your camera is level (no tilted horizons). If indoors, aiming the camera down or up a little makes the walls lean in or out. All of this is seen in the viewfinder if you simply think to look at it, and you can straighten it there. But outside or indoors, do hold the camera level (so that the walls are not seen leaning and any wall corners are vertical).
- Always remember to check your ISO, because you may have forgotten that you changed it. This is very good advice if not using Auto ISO. And my notion is that with more experience, the less you will allow Auto ISO (preferring to set it yourself to what is actually needed instead of letting automation meddle with it). There might be times to use Auto ISO, but as an oldtimer, my Auto ISO is routinely always off. And note that Auto ISO cannot adjust a manual flash, which absolutely CANNOT work with Auto ISO (if ISO changes).
- Time of day can be important for outside pictures in the Sun. Photographing a building or mountain may not be best if it is in shadow then. For some planned important picture, plan your visit time too. The first hour after sun rise and the last hour before sunset are considered great light outdoors (called the Golden Hour), and high Noon may be the worst (harsh shadows, etc), so consider finding some shade then. But there are always exceptions, noon might be the only time the street between the tall buildings gets any sun at all.
- Simple is often better than complex. Don't overdo anything, including your scene content. To get what you want, have a reason for your choices.
Your camera meter will pick some combination with a correct exposure, often fine enough for some routine everyday snapshots with no special requirements, but for anything "different", maybe another different combination is the best choice
for a particular photo situation. You decide if the metered exposure is the best you can do, or if this scene is a special situation needing human intervention. So we change it first to fix problems if something else is better. The decision can become a compromise, but you help the worst case. You may not realize yet how easy and satisfactory this is, but a little experience (of thinking about it) will work wonders for your photography.
To Begin Photography
The first day might be a little difficult, but after learning about a few things, experience will soon come, which completely changes the game. Take lots of pictures of all kinds of scenes, and look at the scene first and examine the results closely after, and find the special situations that cause problems. Think about how the problem can be averted. You will learn for years, but major results come fast with just a little experience.
If interested in learning photography, a faster way is to check Google for a search on the words Photography Class and your city name. Often local camera stores or community colleges offer after hours classes. You will need an adjustable camera. Or ask around locally too, like at the camera stores. Friends that are actually into photography can be a big help.
Also Google for the words Camera Club and your city name. There will be lots of help there, and they might have classes too. Now and then take in some of your problem photos (and know their exposures, f/stop, shutter speed, and ISO) and ask about them.
Otherwise, I would at least suggest Bryan Peterson's book
Understanding Exposure, Fourth Edition: How to Shoot Great Photographs with Any Camera
which has become very popular, THE modern classic about beginning photography.
Specifically, it is about the basics of using shutter speed and aperture and ISO, the first basics of photography that we absolutely must know. When and why you might need to chose a different camera setting. If you don't realize how that helps, then you really need a book like this. Any photography class (which would be good too) would have to start with these first fundamentals. Because without someday learning them, you'll never advance beyond your smart phone camera point&shoot. Learning ability to have control over your pictures is so much better.
This book is about using adjustable cameras with manual control of aperture and shutter speed and ISO (to be able to control your picture results) which need not be at all spooky, because it is very definitely a beginning first day level book, and a very good one, the first step for newbies, but extremely important to know to ever get off the ground. This is what photography is about, and to have any control in our pictures, we absolutely gotta know this most basic stuff. This book should be any beginner's first photography book to start them down the road in the right way. By "beginner", I don't mean about how many years taking pictures with your cell phone, but instead about anyone wanting to get out of fully automatic mode, to have ability to select settings to best match the situation, to create the picture instead of just point&shoot. Peterson's book is a similar subject as this brief page, but extremely well explained, and Not deep, Not techie, and with many large pictures, It is a very easy fun read about how the first basics of photography work, about using shutter speed and aperture and ISO for exposure of special situations. This book has developed a wonderful reputation about being very effective to get beginners started right, they like it. There is more to its subject than just "Exposure" — it is about the Whys of your choices. When you know why, you know how. The newest edition has added an introduction to flash, but primarily this book is about photos in regular continuous light, sunlight and light bulbs. If aperture and shutter speed are still any mystery, you need this one before all else.
The book is not expensive, but its price has recently gone up. This book is about $24 now, and if you are a beginner (actually interested in starting real photography), then this is easily the best $24 you can spend on photography. This book will may also be in your public library (the older versions are good too). And the second hand previous 3rd Edition can be ordered on Amazon for around $5.50 including shipping. It will do the job too, but the 4th edition is very nice.
If interested in learning photography, you'll enjoy this book (see the user review comments at Amazon). But at minimum, this Exposure subject is on Google ( Exposure Triangle ). There is no triangle involved, (so don't try to figure out any actual triangle), it only tries to mean there are the three factors of Exposure, the three combined into one exposure value. And there are Equivalent choices for different reasons.
Other than the above Exposure topics, there are more things to be learned. I suggest looking at Google too
Tips improving your photos. And substituting the word photography for that search word photos is a little different list, maybe more about composition. Both are large lists of many things.
Here at this site (which is more about how the equipment works), there are pages maybe a little advanced beyond first beginner level, see the Main page menu.
Photography is a learning experience, and you will continue learning for years, but a little experience works wonders, and most cases are obvious and easy, but simply require attention. First, you must look a the , and actually see.
We don't actually compute motion blur or depth of field numbers for each picture, instead we just learn that action pictures need a faster shutter speed (or a speedlight flash). Or that some pictures need more depth of field, stopping down aperture or using a shorter focal length is all that is possible. These two ideas can conflict about exposure however, and what is possible becomes important, meaning we still have to make all three factors of shutter speed, f/stop, and ISO combine to match the correct exposure (use of Equivalent Exposures). This becomes easy and second nature with a little experience. It does mean we have to think a bit about what we're doing, but we can usually "just know", and then we simply do what is necessary as an automatic reflex. We just know what to do (because we have experience thinking about things before). So for starters, remember to think about looking and thinking about what you are doing.
The camera light meter exposure is a starting point, often pretty usable in many average scenes, but the meter cannot recognize the scene or its issues. It just provides an exposure "not too dark, not too bright". Abnormal bright or dark areas in the scene can fool it. A good example of situation that a beginner with the non-adjustable camera cannot handle is an indoor subject standing in front of a big window with bright sunshine outside. Or same thing is a person under a shade tree with the bright sunlight behind, beyond the tree. The camera light meter cannot recognize know what the scene is, or what it needs, or if it has a bright background, or if it contains fast motion, or needs greater Depth of Field, or whatever, etc. But these are not difficult situations for a photographer who stops to think a second about what they see. In worst case, they can realize why they may need to select a better scene situation. 😊
Exposure is determined by the combination of aperture, shutter speed and ISO. If you increase one of the three, you normally have to decrease the effect of one or both of the other two to keep the same Equivalent Exposure. This combination is sometimes called "the Exposure Triangle", only meaning these are the three factors of exposure, shutter speed, f/stop, and ISO, which combine into the actual exposure. Exposure Triangle is a good search term, but there is no actual triangle). Before we click the shutter, we just take a brief instant to consider if this first metered combination is fully appropriate for the scene situation.
- Shutter speed is the duration time that the shutter is open to pass light. 1/100 second shutter speed is 0.01 second duration. More time is more light (brightening a too-dark image). Fast shutter speed is also used to freeze motion but then it also passes less light. A slow shutter speed can intentionally allow motion to blur (blurring water falls is one popular purpose), and it passes more light. If fast motion is present, a faster shutter choice like maybe 1/1000 second would be necessary to freeze it. Or 1/200 second should handle reasonable motion, like walking. If there is no speed problem for a motionless scene, just hold the camera steady or use a tripod.
To compensate for a faster shutter (which is less light), simply just open the aperture some (smaller f/stop number), or increase ISO some (greater ISO number), either one is more light. Or do both if needed in more dire situations.
Twice or half shutter speed duration time is 2x or 1/2 the light, called 1 EV (Exposure Value), or is causally called "a stop". A "stop" originally meant the click stops (detents which could be set by feel) on the shutter and aperture dials, which in the old days, only did full stops, so one click was called one stop (for any of shutter speed, aperture, or ISO). Today, the camera also has third or half stops for finer precision steps, so that's more clicking now. But one full stop is a term for 1 EV, which is 2x exposure. Going the other way is 1/2 exposure, usually called -1 stop or -1 EV. Once you get into this, it will come easy.
Camera settings are marked on the camera in rounded approximations called Nominal values (these exact numbers are not necessarily actually implemented in reality, but Nominal numbers are a 100 year old marking convention, and may be easier for humans). But modern camera design knows to instead actually implement (the best that it can do) the Precise Design Goals with exact 2x full stops, but which are still today marked with Nominal numbers.
|Full stop Shutter Speeds, seconds
I hope this is not confusing for a first day beginner, but I wanted to show the Nominal settings you will see on the camera. Again, there are also third or half stops between each full stop, which you can see these values in these large charts. It won't take long to discover you will have most of these numbers easily memorized.
- Aperture (f/stop) is the size of the lens opening, and aperture size can be adjusted (called f/stop). Wider diameter with larger area (and smaller f/stop number) allows more light to pass through the lens (for the time specified by the shutter speed). Double or half the area is 2x or 1/2 the light, which 2x step ± is also named 1 EV. The camera also has third or half stops for finer precision. Aperture is dimensioned in f/stop numbers. The f/stop NUMBERS themselves increase in √2 (= 1.414) steps, but each full stop is 1 EV.
The f/stop NUMBER is calculated as ("lens focal length" / "effective aperture diameter"). That nomenclature may be a little awkward, but the purpose is that f/stops have the very important property that a value like f/8 is the same aperture exposure on any camera lens also set to f/8.
|Full stop f/stops
A larger aperture diameter (smaller f/number, maybe f/1.4) is more aperture exposure. Or stopping down (smaller diameter, larger f/number, maybe f/16) can also be used to increase Depth of Field sharpness. Focus can be at only one distance, and focus is acceptably sharp in a zone either side of focus distance, with acceptable sharpness in that zone called Depth of Field. The Depth of Field zone can made larger by a longer focal length, or by stopping aperture down more, maybe like to f/16 or even f/22 (which allows less light, so then to compensate, exposure will require slower shutter speed or higher ISO, Equivalent Exposures). Either end of the extremes (wide or narrow) of lens aperture is less sharp than the middle range. Wide open has optical aberrations and minimal Depth of Field. Stopping down aperture extremely increases Depth of Field, but also adds diffraction (distortion hurting resolution, but the greater Depth of Field is sometimes worth it). So there are times and reasons to choose these values reasonably carefully. Small cameras (like cell phones with very short focal length) have extreme range of Depth of Field, but it can be a concern in larger cameras.
- ISO is the sensitivity to light of the sensor ("film speed" so to speak about older days). Increasing ISO is another choice allowing more exposure, meaning it then allows either or both faster shutter or stopping down aperture more. Digital cameras can simply change ISO with a dial. Lower ISO 100 may be better image quality but high ISO is often needed to allow faster shutter speed or stopped down aperture. Larger cameras have an advantage, but at some point, excessively higher ISO can add image noise which hurts sharpness and clarity.
- The combined Exposure is the three factors combined: This best choice likely varies for different reasons in different scene situations, so you first just actually look at the scene, so the situation details will register with you, and then make appropriate adjustments as seen needed. Unless of course, you simply can't be bothered to think about what you're doing. 😊 Seriously, consciously creating the best pictures is a very popular hobby, and even a business for some.
A light meter can only measure the brightness of a blob of light, but cannot recognize the scene or its needs. So the decisions about the scene situation require a human, with eyes and brain, which can analyze and understand. So remember, a fully automatic camera is trying to create a picture that is "not too dark, not too bright", but it simply doesn't know more, and couldn't care less. There are ordinary pictures that a cell phone just can't do. For one example again, if there is a bright sun background behind a subject in the shade, or indoors aimed toward of a bright window behind, the meter doesn't have a chance without help. Just give a quick thought to what you're doing, because that's what makes the magic happen. There is joy in the results when you know how to get it right.