An Exposure calculator to compare EV value and stops difference for any two camera or meter exposures is on the previous page.
Learning exposure is an extremely important initial skill in learning photography. Exposure of a photo obviously depends on the combination of the three factors, f/stop, shutter speed, and ISO. There are several possible combination choices (Equivalent Exposures), but usually one best one for the current scene. See Google at "Exposure Triangle" for more basics of learning this, which is about the first elementary concept photographers need to know about Exposure. "Triangle" is the name used, but it is figurative, cute but possibly confusing, since there is no triangle, there are just the three interacting factors controlling exposure (f/stop, shutter speed, and ISO).
BTW, in "things we need to know", if the Google search terms are actually a known phrase, like "Exposure Triangle" or "Field of View" or "Extension Tube Formulas", then add the quotes around your search phrase so Google will search for it as a combined phrase. That can at times improve search results. Then "Crop Factor" won't include the individual words like "rain is a factor of crop growth".
There are always several equivalent exposure combinations, and the skill (to get out of Full Auto mode) involves knowing when and why you might give preference to each of those three factors (when to do what?) Fully automatic cameras do not aid learning this. A cell phone won't offer more, and point&shooters won't even know what camera settings were used. But you are standing there looking at the scene, so you could be thinking about what is most important to this picture? That's what a photographer does.
The trick is to stop and look and think just a second. What are you trying to do? Does it need fast shutter speed to freeze motion, or slow and a tripod? Does it need stopped down aperture for greater depth of field or open wide to blur the background, or to help the flash power? Or maybe low ISO to minimize noise, or high ISO to make the rest be possible? Is your subject in deep shade but with a bright sunny background behind them? (Auto can't work then without your intervention and help). So what is important at this scene?
A light meter just measures the intensity of a blob of light, but it has no human brain to recognize the scene situations to know which Equivalent Exposure combination is best. But you are standing there with the needed brain, so use it. This is your job. Beginners don't always realize these things can be considered first, but this becomes automatic and immediate and easy and obvious with a bit of experience. You see the scene when you walk up, but beginners may not yet realize they need to stop and look and think just a second. These goals can conflict in tough situations, to sometimes be a compromise when you can only do what you can (which is still best choice), but when you know why, then you know how.
If you're having any trouble beginning, an inexpensive good book (likely already in your public library) is Understanding Exposure, How to Shoot Great Photographs with Any Camera, which is about the basics of how to use the camera settings. It's a short easy fun read (with many full page pictures), and it is popular with a huge rating (and has become a classic) to convey the basic first principles so extremely important to photography (The used previous Third Edition is only about $6 total at Amazon.) And Google at Exposure Triangle should help too.
There are concepts of relative EV adjustments, or of absolute EV values.
One major use of EV (Exposure Value) is just to measure any change of exposure, where one EV implies a change of one stop of exposure. Like when we compensate our picture in the camera. If the picture comes out too dark, our manual exposure could correct the next one by directly adjusting one of the three exposure controls (f/stop, shutter speed, or ISO). Or if using camera automation, the camera meter is controlling it, but we might apply +1 EV exposure compensation (or +1 EV flash compensation) to make the result goal brighter, as desired. This use of 1 EV is just another way to say one stop of exposure change.
Why not just say "stop"? I don't know, I suppose only two characters is easier to mark in the camera controls. In film days, both lens f/stop and shutter speed dial had mechanical click stops, but ISO was another roll of film. But we still had to tell the camera metering system which ISO, and that ISO dial had click stops.
But regardless, one stop is an exposure factor of 2 (2x more or 1/2 less). One EV is a step of one stop compensation value (could be aperture, shutter speed, or ISO, or some combination). This +1 EV means a one stop greater exposure. I assume this basic compensation use is already known. The rest of the page is about the absolute EV numbers.
Adjustable cameras offer relative Exposure Compensation and Flash Compensation to correct exposures by few EV. Specifying compensation as +EV means to add more exposure to correct a dimmer light. And -EV means use less exposure to correct a brighter light. The metered EV is what we actually have, more means brighter (requiring less exposure). And then compensation is the correction about what we actually need, more compensation to make it brighter. Compensation is a Relative EV number.
A light meter reads a higher EV reading to mean a brighter light requiring less exposure. In the EV Chart at bottom of this page, the highest EV numbers use the least exposures. Bright light meters higher EV, and dim light meters lower EV. These are Absolute EV numbers, but which apply to whatever the ISO being considered.
The light meter measures the scene light brightness value, which is the EV reading, for example bright sun is often EV 15 (if ISO 100, or EV 16 if ISO 200). The EV 15 row of the EV Chart will show Equivalent exposures typical of bright sun and ISO 100. The camera settings of ISO, shutter speed and f/stop can match the exposure to that light reading. Another first basic of photography is Equivalent Exposures. There are multiple different settings that can give the same exposure, called Equivalent Exposure. For example, we can increase the shutter speed faster to be half duration to reduce the light seen (like from 1/100 second to 1/200 second, which is one stop less light, called -1 EV), and also simultaneously open the aperture one stop to increase the light seen, like from f/8 to f/5.6 (one stop more light, called +1 EV). These changes can be chosen to balance and cancel so that we still get the same exposure. Called Equivalent Exposures, these two relative changes combined both compute the same absolute numerical EV (details follow).
One first basic skill fundamentally needed in "photography" is in learning which of these equivalent exposures is better suited for our current picture, knowing which equivalent choice to choose for the picture. For example, changes in shutter speed may better stop motion, or changes of f/stop affect the depth of field, so we can choose settings to improve the picture result, but the exposure can be the same. You choose the most important factor for your picture. If the EV result is still low, then you need more ISO too. Composition is important too. The light meter automates basic exposure, but actually learning "Exposure" really means learning which of these equivalents is the right one this time. The meaning of Equivalent Exposure is, change the shutter speed, but equally compensate with the f/stop, and it is still the same Equivalent Exposure. Compromises may sometimes be necessary, but still, often there is one best equivalent choice. It might be said that cell phone camera users don't know the details, and the camera does not offer any controls anyway, so the difficult jobs are always a problem, even if they're happy with most pictures.
Equivalent Exposures relate to any normal continuous light, generally any daylight or incandescent lighting, but Not flash, flash is not continuous light. Speedlight flash exposure is faster than, and independent of shutter speed, so it has no same concept of equivalent exposures. But all Equivalents are not Equal — as always, there are ifs and buts. :) Yes, equivalents are the same exposure (regarding brightness of the picture), but freezing fast motion requires a fast shutter speed, a slow shutter won't do. Maximum Depth of Field requires stopping the f/stop down, a wide aperture won't do. Fluorescent lights with magnetic ballast do seriously flicker that the camera captures, causing possible color problems except at specially considered slower shutter speeds (CFL bulbs and electronic ballast are OK). Television screens also need a slow exposure (1/30 second is typically OK). There are many considerations, and there are better and worst choices of Equivalent Exposure, and there is often good reasons to choose the one best one.
EV is named Exposure Value, which sounds like an "exposure", and it is, but the EV chart does not measure light. The EV chart (below) is simply about combinations of numerical camera settings of shutter speed and f/stop. An EV number represents a set of camera settings, regardless if it is a proper or accurate exposure or not. But in use, it involves ISO too. A light meter could measure the light, and tell us EV at some ISO, then we look up the Settings in the EV chart for proper exposure at that ISO. EV basically gives a name to the group of several "equivalent exposure" choices comprising any one row of the EV chart below. Each row is a one stop step from its adjacent rows. A 1 EV step is one stop. This one stop step could be due to a light change, or a setting change, or an ISO change. When the camera compensation changes the camera settings by one stop, it calls it one EV. But the main concept is that this row of settings contains "equivalent exposure settings", identified as some EV number.
The EV concept was developed in the late 1950s, as a computing method to be able to add light meters into cameras for the first time (which became the common practice in the 1960s). Film cameras used the current roll of film, with its predetermined ISO, so ISO wasn't technically a camera setting yet (but it was a light meter setting). Yes, there certainly are the three variables of exposure, but light meters measured light and computed shutter speed and f/stop for that existing film ISO. And this separation of ISO is in fact how the actual exposure formula works too (next).
You should have heard all the uproar complaining back then (early 1960s) about the concept of meters actually being in the camera. There was no internet yet, but monthly camera magazines were very popular back then as about the only current communication, and they exploded with articles about could we trust a meter in the camera? But that wasn't about the accuracy of the meter reading (in fact, the "through the lens" metering was a big advantage for reflective metering, it saw what the lens saw). The debate was about the control of the camera, about the necessary skill of selecting the proper Equivalent Exposure for the situation. Could a dumb computer replace the human brain to recognize the situation? There is a little more to that, and camera chips are still too dumb to recognize the situation, and it's still a very good question for any difficult situation. Meters do need human help to recognize the situation, but we obviously do need a light meter, and a photographer makes good use of their eyes and brain too.
Some EV math computing details are on anther page here if interested in calculating — but relax, you don't need to know the math to take pictures. We normally don't even need to know EV number. It is part of how things work, and a glance might be interesting, but we can rely on the light being metered, and the EV Chart shows the EV numbers already calculated. But EV is the topic here.
The EV formula, see Wikipedia EV
N is f/stop Number, t is duration Time of shutter speed — the camera settings.
Log₂ creates EV as an exponent of 2:
The reflected light meter Exposure formula:
See Wikipedia light meter calibration
where L is the scene luminance, S is the ISO sensitivity, and K is a constant typically 12.5.
The only purpose here is to just show there is a formula where ISO adjusts the scene luminance to match a proper exposure with the camera settings expressed as EV. We don't have to know it, but it is how light meters work. Meter results show one of the setting combinations, or some meters can show the EV number too.
A special trick is to note that the f/stop Number in any Exposure EV calculation is always squared (N² above). Because the Number is √2 steps, but EV is steps of 2x. √2² = 2. N may represent the f Number, but N² represents the aperture exposure. But shutter speed or ISO values are NOT squared, because their full stops are steps of 2.
This is because f/stop number = focal length / aperture diameter. The circular area determines the exposure and circular area = Pi r²
EV 0 is f/1 at 1 second: Any number to the power of zero is one, so 20 = 1 = 12/1, so f/1 at 1 second computes EV 0. The exponent is log2(1) = 0 EV. This is the math of EV. See more of the EV math here.
(the value of X) log ÷ 2 log = log2(X).
The EV number (for any one ISO) can represent several equivalent exposures (using several camera shutter and ISO setting combinations) computing the same EV (Equivalent Exposures, like f/2.8 and 1 second, or f/4 and 2 seconds). Any one setting combination is on only one row of the EV Chart, and those Equivalent Exposures make up that one row. Exposure Value (EV) represents the light level, as adjusted by the selected ISO. If a different ISO were selected, it would compute a different EV which would be different camera settings. And the log₂ causes 1 EV to be powers of 2, i.e., exactly a 2x exposure change. EV is very important to our light meter's exposure calculations. The EV value alone is not actually an exposure, because exposure also needs the specified ISO, which is very important to make a match, even if ISO is not a direct factor of EV. EV is a reaction of exposure to the scene light level and ISO. Then the EV value determines which other camera settings that will match the scene light level. This EV calculation is just a scale with 2x stops, proportional to f/stop number squared, and inversely to shutter speed.
The EV formula does compute EV using only f/stop Number and shutter speed, so some "experts" claim EV is independent of ISO. It is true that there is no term for ISO there, but it's not that simple. An absolute value of EV is quite meaningless without a specific associated ISO, because any camera exposure setting numbers of interest to us were determined by the ISO choice. Exposures in direct bright sun normally meter near EV 15 at ISO 100, or the same light is near EV 18 at ISO 800. EV does determine the appropriate settings for the ISO number we use (and for the existing light level).
The ISO is set, either by the roll of film, or by your digital settings. Then the light meter reading at that ISO determines the row of equivalent exposures (like the row in the EV chart below). Fully auto modes cannot recognize if the situation is special (regarding motion to be frozen for example, or that the depth of field needs to be extreme), but do try to keep shutter speed not excessively slow if possible. Auto ISO automation may change ISO for other numbers (is 1/2 second too slow? Is f/1.8 too wide and fuzzy? Higher ISO can be a solution then.)
Anyway, the EV number is determined by the light meter from the luminance of the scene and by the ISO film speed (ISO was called ASA until 1974). This single EV number represents the group of shutter speed and f/stop combinations that all match the proper exposure, called Equivalent Exposures. This set of Equivalent Exposures (of one EV number) were all the "same exposure", which was a huge plus for using exposure, but not quite the same as "same picture", because f/stop affects depth of field, and shutter speed affects the degree of freezing motion blur. The light meter gives us an exposure, but the basic skill of photographic exposure involves evaluating the proper combination of the Equivalent Exposures, knowing when to choose what (basically deciding the relative importance of the need to freeze action or to increase depth of field), which every photographer seriously needs to learn. This topic of control is often named Exposure Triangle, simply because there are the three interacting exposure factors involved (the actual graphic "triangle" adds nothing else to the concept).
A brighter light, or a higher ISO number, meters a greater EV number, so less camera Exposure is needed. A greater EV number is a lower row in the EV chart with faster shutter speeds, which is less Exposure. EV number is about the necessary camera settings to match the scene and ISO. EV number increases in the opposite direction from the Exposure required (one EV is same amount as one stop, both are a 2x change in exposure).
To clarify a common misunderstanding, exposure depends on luminance, which is the average light per unit area of the scene, and which is NOT about the total area of scene or sensor. Photo exposure is NOT affected by the size of the sensor. If it were otherwise, hand-held light meters would be useless for differing cameras (and they certainly are Not useless). A scene (for example containing a dark shadow area with a bright patch of sun near it) will contain several areas of different exposure, and the trick is finding the one camera exposure suitable for the mixture. Camera automation can only try for a middle or averaged value; not too bright, not too dark. Unfortunately, this is true of reflected meters regardless if the subject ought to be quite bright or quite dark. Without your help, the metering result will come out as a mid-level value (see How Camera Light Meters Work).
A reflected meter (like in a camera) reads the light reflected from the subject. Whereas an incident meter does not even see the scene. It is instead aimed from the subject towards the camera, to measure the actual incident light falling on the subject. Both reflected and incident meters center the exposure on their average reading. The incident meter has the strong advantage of Not being affected by the variable colors reflected by the subject (green reflects brighter, blue reflects dimmer, affecting reflective metering). But it means more than that.
If a reflected meter sees a mostly black or dark-colored subject area (colors that do Not reflect well), it reads a dimmer light, and puts it at mid-range, and the picture turns out gray (brighter). If it sees a mostly white or bright-colored subject area (colors that do reflect well), it reads a brighter light, which it puts at mid-range, and the picture turns out gray (dimmer). If it sees an average subject with a mix of average colors from dark to light color, averaging middle, it puts it at mid-range, and it comes out good. Meters cannot recognize the subject to know what it is or how it should be, they can only put all exposures at mid-range. But photographers know and can see the subject colors and know how it will come out, and can make corrective actions. Which was important in film days, but with digital, we can preview it and get a second chance.
In contrast, an incident meter reads the incident light directly instead of the subject reflections, meaning brighter white things actually will be white and darker black things actually will be black. Which is great, however an incident meter reads the light at the actual subject location, instead of in the camera, which can be more awkward to use (it's Not point&shoot). Incident metering is on the third page of How Camera Light Meters Work.
Light meters usually convert the light reading to camera setting values. We tell the camera meter the ISO value. Then:
But these next pictures are of a meter mode to show the EV reading directly. These are a Sekonic L-308S metering EV exposure in brightest sun. The incident meter sees the light directly (meter aimed from subject toward the camera instead of vice versa), and then the light reading and specified ISO compute the EV. It makes the point that EV certainly varies with ISO. Bright direct sun will be near EV 15 at ISO 100, which one choice is 1/125 at f/16. This was Texas, 3 PM in mid-February, very clear sky. Note that days and skies can vary slightly, and the previous very similar very clear day try metered 0.2 EV lower (haze, humidity, etc). EV mode reads in tenths. Tenths are very handy for metering multiple manual flash (studio situations). Then for example, some other tenth stop metering in f/stop mode might be read as f/8 plus 7/10 EV. That does NOT mean f/8.7, but instead means 7/10 of the way to f/11, which is about f/10 (more or less f/8 plus 2/3 EV).
This example shows how the one standard EV Chart is good for any ISO (or rather, specifically good for whatever ISO that you used to measure it). Both pictures were taken within a few seconds in same sunlight. The point is, ISO certainly does affect the EV number. There is only one standard EV chart (for full stops). A row of Equivalent Exposure settings are indicated by the EV number. EV is that chart row of Equivalent Exposure settings. That EV row applies to whatever ISO was used to measure it.
On the EV 15 row in the EV chart below, you can find the settings f/16 1/125, which the EV 15 row number tells you those settings are EV 15 (for the ISO being used). But if you look on the EV 18 row (on this same standard chart), you find f/16 1/1000 second, which is +3 EV, which row is correct exposures for EV 18 (for an ISO 3 EV higher). So for whatever ISO it may represent, just look up the EV on the EV chart. Or look up the settings to find the EV (for the ISO that causes those settings). That is why it is the standard chart. The EV formula computes the standard chart for any use. We can't say "EV is independent of ISO", because a specific ISO has already influenced the situation, either the meters EV reading, or the camera settings selected.
Bright direct sunlight is normally near EV 15 at ISO 100, or near EV 18 at ISO 800. In both cases, a light meter set to that ISO will read that EV value. The metered EV 15 row will show the correct settings for ISO 100, and the metered EV 18 row will be correct for ISO 800. On this one standard EV chart.
Any one row of the EV chart shows the Equivalent Exposures at THAT EV, for that ISO that measured the EV.
Wikipedia has an ISO 100 chart of typical EV values for many types of scene lighting conditions, some of which might be difficult to meter.
Used like this:
We can meter our bright sun scene as EV 15 at ISO 100, and look up EV 15 in EV chart, to see f/16 at 1/125 second settings to be used for exposure at ISO 100.
Or we can meter EV 18 at ISO 800, and look up EV 18 in EV chart, to see f/16 at 1/1000 second settings to be used for exposure at ISO 800.
Either setting would be the proper metered exposure at the ISO specified. Any of the Equivalent Exposures on the same row of the EV chart are the same exposure too. Anyway, ISO 800 meters 3 EV higher than ISO 100, and the camera exposure will require settings 3 EV higher too.
Sekonic meters call it EV mode. Meters for photography show the "EV reading" of the scene computed for the ISO specified, which varies, so if for a standard comparison, the term Light Value is converted to ISO 100. Unless using ISO 100, this is Not the EV values that meters show, but it can be converted.
The light meter's EV mode will indicate camera f/stop and shutter speed settings directly at the specified ISO, which combination of settings is found on only one row of the EV chart. The meter basically can do the EV chart lookup for us. So absolute EV is not a concept we really need for photography now, but it is still valid, and the rest of this page should help to explore the numbers.
When no light meter is available, the Sunny 16 Rule on next page offers approximations for several outdoor daytime situations. It was generally included on a printed sheet with every roll of film sold. Bright sun often reads EV 15 at ISO 100, which could be f/16 at 1/125 second. The Sunny 16 Rule is based on bright sun being f/16 at shutter speed of 1/ISO seconds, for example 1/100 second at ISO 100. That is a 1/3 EV difference, but pretty close, certainly ballpark. And some days bright sun often reads a bit less (variations in the atmosphere haze), making them very close.
Half stops are marked with *½
EV charts normally only show only full stops for EV and settings. A third stop difference wasn't much for B&W negative film, easily adjusted in the darkroom print, and much older cameras likely only did full stops. However, EV charts for third stops and half stops have also been provided below.
The EV number takes into account only the shutter speed and f/stop settings (but which were chosen of interest for some specific ISO value). To provide comparisons, "Light Value" is a conversion of the EV number to be the same exposure at ISO 100 (below). ISO 100 is a nice arbitrary standard choice, convenient maybe, and very popular but not special in any way. 100 is just a number, with no special significance (humans just see it as a nice round number). The EV Chart is NOT about ISO 100, it is about whatever ISO you are using at the time.
In bright sun, the photo above shows ISO 800 was metered as EV 18 (the settings necessary for ISO 800). And the EV chart shows f/16 at 1/1000 second is EV 18, so that works if using ISO 800. And if we compute EV of those settings, we get EV 18.
But ISO 100 metered EV 15 (the settings necessary at ISO 100), which is a different row in the EV chart, and different settings of f/16 at 1/125 there, which also work if using ISO 100. These different settings will compute that EV 15, which due to ISO, is an Equivalent Exposure. ISO determines proper exposures for the settings, so to speak, and exposure cannot use the same settings at different ISO. So it's just different situations. Different light brightness does meter different EV values, requiring different settings. Then simply look up the proper settings on the correct EV row. Only one chart EV row has Equivalent Settings for that EV.
A chart of estimated exposures for many common situations is at Wikipedia. Nothing like that can be precise, but it should be a good starting point. The EV chart below will give Equivalent Exposures for their EV value. Note that the Wikipedia chart is for ISO 100. ISO 400 for example is numerically 2 EV greater.
The EV chart shows rows of Equivalent Exposures for a given light level. Each row is a light level measured in absolute EV. If you find your metered exposure settings in the chart, that row has other Equivalent Exposures for the same light.
The EV chart shows camera shutter speeds, in seconds. It "shows" nominal stops, but it computes precise stops. The combination of a f/stop with a shutter speed is the camera settings which comprise the EV value. Any such combination can appear on only one row of the chart (row is called EV). The EV chart is about the numerical combinations of the shutter speed and f/stop values, and the resulting exposure at some ISO. Specifically, an EV row is the list of Equivalent Exposures for that EV. ISO is of course an exposure factor, it matches the settings to the light. Instead of computing the math, the chart could be drawn by just starting at f/1 at 1 second is EV 0, and then adjacent values differ by one step (usually steps of one stop).
Again, the EV formula and the EV chart are NOT about any specific ISO value (and certainly NOT only about ISO 100). When you might realize that its values are appropriate for ISO 100, and then imagine ISO 100 must have some special meaning, you should also notice that the chart values are also appropriate for any other ISO that is metered or that gives a correct exposure. The chart is appropriate for any ISO. Our common usage may condition our brain to favor thinking of ISO 100, but the EV number in the chart is determined by the settings we choose for any ISO we are using. Not necessarily ISO 100. ISO 100 is simply just another number, special only because our memory may be conditioned to think of it first. The EV number is technically computed only from the f/stop and shutter speed, but any proper exposure is then due to that ISO used. Higher ISO increases the EV number for the same scene light value (needing different camera settings). All I am saying here is the EV Chart is NOT about ISO 100. It is good for whatever ISO you are using, which does include ISO 100. :)
In normal usage, if your light meter meters bright sun to be EV 18 at ISO 800, then you look up EV 18 in the chart, which row gives the Equivalent Exposure settings for use to give a correct exposure at ISO 800. f/16 at 1/1000 second for example. The scene light is NOT EV 18, that number depends on the ISO. The camera settings are EV 18 to match the scene at ISO 800.
If using ISO 100 and the light meters as EV 15, the correct camera settings are on the EV 15 row.
If using ISO 800 and that same light meters now as EV 18, the correct camera settings are on the EV 18 row.
If metering ISO 800 and then converting to use ISO 100, that's the same -3 EV that we would always expect.
This chart computes with precise values, but shows the camera's nominal shutter speeds (seconds), except there are no nominals longer than 30 seconds, so then the precise actual values in seconds are shown instead (up to 512 seconds which is 8 minutes and 32 seconds). If curious about the nominal full 2x stops being uneven shutter speed progressions of 1/8, 1/15, 1/30, 1/60, 1/125 seconds, then see the explanation of camera precise values.
There is only ONE definition of EV and EV charts, used for all ISO. For any ISO value, your f/stop and shutter combination in use would appear on only ONE EV row. If your exposure in direct bright sun was ISO 100 f/16 1/125 second, f/16 1/125 is on only one row which is EV 15. If it is ISO 800 f/16 1/1000 second, f/16 1/1000 is on only one row, which is EV 18. The EV is the row where you find your actual used camera settings. The correct way to verbalize these is EV 15 at ISO 100, or EV 18 at ISO 800.
A regular EV Chart normally only shows full stops, normally starting from f/1 (f/1 at one second is EV 0). Our cameras do use third stops, but EV Charts for third stops are never shown because the chart becomes quite large (very wide on the screen). Nevertheless, three EV charts are provided here, the standard EV chart for Full stops, and also EV charts for third or half stops are offered.
Third stops from f/1 to f/32 will fill a 1920 pixel full screen width, but you can limit the range to show only maybe f/2.8 to f/16 (which is then half width). You can also reduce chart font size too.
The "Show Chart" checkboxes toggle Third and Half stop charts to be On or Off (Half stop is Off by default).
These charts are for any and all ISO. If your reading is EV 14 at ISO 400, then your Equivalent Exposures for ISO 400 are on row of EV 14. But doubling ISO is one EV, which will then be the settings one EV row lower, at EV 15.
So we don't need EV chart versions for each ISO. The chart is for the ISO you are using. There is only one standard EV chart. It works for any ISO, for whatever ISO is used, and ISO certainly does change the settings selected. We will see a different EV number for other ISO, and there is just the one standard EV chart.
Any possible combination of f/stop and shutter speed (for example f/8 and 1/250 second) appears on only one row in the EV chart. The EV number is the name of that one row (of Equivalent Exposures). If we meter EV xx at some ISO, then EV xx is the one EV chart row which contains the correct exposure settings for that ISO.
EV is named Exposure Value. It is the exposure of the camera settings at some ISO, and is assumed to be a proper exposure. But in the absolute sense (the EV chart), EV technically does just compute f/stop and shutter speed, but it computes with those values that were selected for the specific ISO you are using. EV is certainly about some specific ISO situation. ISO is a factor that will obviously affect which f/stop and shutter speed values you select to properly expose your photo. Just saying "EV 16" has no meaning (other than to describe shutter and aperture equivalent settings). We instead might say "EV 16 at ISO 200", which then defines a useful exposure setting, probably for full direct sunlight in that case.
In the absolute sense, EV needs a defined ISO situation.
In the relative sense, EV is just a relative change in any of these three variables, one EV is one "stop" of exposure.
The EV nomenclature was invented to aid development and control of the first light meters placed into cameras in the late 1950s, back when film speed depended only on the roll of film loaded in the camera. EV camera "settings" are in that context, meaning shutter speed and f/stop, for the film speed that was already defined and in place (for whatever ISO we are using). The old mechanical cameras only had settings for shutter speed and f/stop. However, in use, we still had to set a film ISO value for the meter, so we can meter an EV value at that ISO, and the camera settings are computed from EV (or the EV chart does this too). EV computes only the shutter and aperture settings (for that ISO), and when we use it, we see that EV cannot work without ISO. In use today, we set our light meter for ISO, and it tells us EV (or f/stop and shutter speed directly).
The EV formula may have no ISO term, but EV is computed from the camera settings which are already explicitly chosen to match some ISO to some scene light level for proper exposure — so EV depends on the ISO used. Digital cameras make it easier to change the media sensitivity, but concept is still the same. Change ISO and the EV changes (different settings are required). For a proper exposure of any scenes light level, any EV number applies to only the one ISO value metered (other ISO obviously have other EV, and other settings).
The camera settings (shutter speed and f/stop) determine the cameras exposure of the light. ISO matches the camera settings to the scene light level, which is our goal. Considerations of depth of field or of stopping motion can choose other Equivalent Exposure setting choices (those on same row of EV chart), but the EV number still needs to come out right, for the ISO used. See the pictures below, the EV metered absolutely will depend on the ISO. Set the shutter and f/stop to that EV, and the exposure will be correct.
This is not semantics, it is impossible to ignore that a different ISO will result in a different EV value (speaking of any real correct exposure). EV is the numerical combination of shutter speed and f/stop settings in the camera, which choice was selected because of the ISO used. The EV chart is about the f/stop and shutter setting numbers for proper exposure, which certainly includes consideration of ISO. ISO has been accounted for in the settings that compute EV. Doubling ISO certainly will move us down one row in the EV chart, which is different settings, and a higher EV. EV involves whatever ISO we are using. ISO makes the EV settings correct for some specific level of light. And we certainly do get wrong exposure calculations if we try to factor in ISO a second time.
If in bright sun at ISO 100, the camera shutter speed and f/stop settings are any combination of Equivalent Exposure of 1/125 second f/16 (the row of the EV chart, see below), then these camera settings are EV 15 (that chart row where 1/125 sec at f/16 appears).
In the same bright sun, if a light meter at ISO 800 meters EV 18, then your correct exposure at ISO 800 is on the EV 18 row of the EV chart (Equivalent Exposures are on that row). EV has a value at any ISO, specifically the ISO we are using, in bright sun or in a dark room. In these cases, then both EV 15 (at ISO 100) and EV 18 (at ISO 800) are the correct exposure (of Equivalent exposures).
Hand-held incident light meters often do have a mode to meter an EV value (representing a row of equivalent settings in the chart), as an exposure for the ISO value you select. This could also be used for comparing brightness for non-photographic purposes, like lighting in work areas or plant growing areas. We have come to assume bright sun will meter EV 15 at ISO 100, if we set our light meter and camera to ISO 100.
But today, it is more usual for the light meter to have a mode to directly report the f/stop and shutter speed values to us, instead of a EV value. Those setting will be in the EV chart on only ONE row, so that EV value of that row agrees with metered value at the ISO value used. The meter looks up those settings for us, from the EV value.
The EV chart has infinitely wider use, for any ISO. However, it is common practice for camera manufacturers to specify a certain luminance as an EV at ISO 100, as when specifying metering range or auto focus sensitivity. It is a way for them to specify luminance that we would understand. When they say "EV at ISO 100", then what they mean is these camera settings if at this ISO. For example, the Nikon DSLR cameras specify their metering exposure range as 0-20 EV, qualifying that these numbers apply to a f/1.4 lens at ISO 100. They say this because if you are using ISO 1600, the maximum EV range must be 4 EV less. If it is said that some EV statement applies to ISO 100, then yes, the statement is about ISO 100. Light Value is also computed to be EV at ISO 100 (because 100 is popular and convenient). EV should not be confused with Light Value, but the combination of EV and any ISO becomes a light value (meaning converted to ISO 100 for comparison, more detail below).
So Wow, the EV chart must be for ISO 100, right? No, sorry, that's not the correct interpretation. That's all an arbitrary choice. If we use any other ISO value, like 800, the bright sun meters about EV 18 at ISO 800, and then the chart also provides the correct camera settings for ISO 800 and EV 18 (if assuming bright sun again). The formal LV for Light Value (below) itself simply arbitrarily chooses to compare at ISO 100 (100 being a very popular value).
The EV chart itself is Not about ISO. Or rather, it is about all ISO, any ISO, the one you are using. It is about camera settings for a proper exposure at whatever ISO. Different ISO values in the meter will meter different EV values (meaning, different combinations of shutter speed and f/stop which match that ISO). ISO 400 will meter 2 EV higher than ISO 100 (so we move down two rows in the chart). The EV value is simply the combinations of the equivalent numerical camera settings. The meter is simply measuring luminance at some ISO, and then calling it EV. (but EV alone, without an ISO, is NOT a Light Value, it is just camera settings).
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