In photography, we talk a lot about "stopped": This is the standard measure of exposure where an increase of one represents a doubling of the amount of light hitting the sensor or film. One thing that many photographers do not realize is that the exposure has an absolute magnitude. Let me explain.
RELATED: What's a "stop" in photography?
Exposure values and stops
When you learn the bases of the triangle of the exhibition-Step shutter, aperture and ISO – it is important to know that there are several combinations of aperture and shutter speed that give the same exposure, even if the photo can look different because of the aperture or shutter speed you have chosen. For example, if you did an outdoor portrait and wanted a shallow depth of fieldyou can go with f / 2.0 for 1 / 2000th of a second; Moments later, if you decided to shoot a landscape, you could use the f / 16 for 1 / 30th of a second. In both cases, the sensor receives exactly the same amount of light. The brightness and the exposure of all the pieces will be identical, but the photos will be totally different because of the different aperture and shutter speed.
But how do you know which combinations to use? Of course, you can go there by trial and error, but there is a definitive scale that is rarely taught. The values f / 2.0 for 1 / 2000th of a second and f / 16 for 1 / 30th of a second have an exposure value of 100 ISO (EV100) of 13. There are many other combinations that also have a EV100 of 13 as f / 8 for 1 / 125th of a second or f / 4 for 1 / 500th of a second.
And that's where things get even more orderly: an EV100 out of 13 actually corresponds to actual lighting conditions. A cloudy day or the sky just before sunrise usually has an EV100 of 13; any combination of aperture and shutter speed that also has an EV100 of 13 will work perfectly.
Why the value of the exhibition deserves to be understood
Before going any further, I would like to take a step back and explain why EV deserves to be understood; it is unlikely that you will need to analyze EV tables to calculate the shutter speed to use when shooting.
Instead, what gives you an understanding of EV is a deeper understanding of what your camera is doing and why. I am convinced that every photographer can take advantage of what happens with their camera when they press the shutter button. It's this kind of knowledge that allows you to choose the right light meter mode or autofocus settings without just guessing.
For me, find out more about the value of absolute exposure also made click. All these abstract discussions about the judgments suddenly took on a real and concrete meaning. I could understand why some combinations were equivalent. So, do not feel the need to memorize all the values of this article; just try to understand them.
The EV100 scale
The EV100 value of 0 is the combination of an aperture of f / 1.0 and a shutter speed of 1 second. Everything else is based on that. This means that your camera and lens can use EV100s between -1 and +21 without using an additional kit. That's one of the reasons you need special equipment to take good pictures of the night sky which has an EV100 between -3 and -11, depending on the state of the moon, stars and aurora.
Here is a complete table of values of the EV100 from Wikipedia. It shows very well which combinations of aperture and shutter speed correspond to which electric vehicles.
More interesting, I think, that to see how the shutter speed and aperture match, is to see what level of light corresponds to which EV. Even if your camera can reach +21, EVs are unlikely to be much higher than 16 in the real world.
|16||Snow on a sunny day|
|14||Hazy, some clouds|
|12||Overcast, shady areas on a sunny day, sunrise and sunset|
|9 to 11||Just before sunrise and after sunset, the blue hour.|
|8||Bright street light, bright interior lighting|
|5 to 7||Inside lighting. Light of the window.|
|2 to 4||Dim light from the window.|
|-1 to 1||Black morning before sunrise, black evening after sunset.|
|-2 to -3||Moonlight from a full moon.|
|-4||Moonlight from a gibbous moon.|
|-5 to -6||Moonlight moon, bright aurora.|
|-7 to -8||Stars and starlight.|
|-9 to -11||Center of the Milky Way.|
The table above is approximate, but precise enough. There will always be variations, but if you follow them you will not be too far away.
Using the value of the exhibition
As I said earlier, understanding the exposure value is more useful for your photography in an abstract sense than in a practical sense, but that does not mean there is no way of not 'use.
If you are long exposure shot with a neutral density filter, you can take your test photos without filter, then add the filter, add whatever the filter stop value to your current VE and set your new shutter speed setting to help of the table EV above. You can also use a EV calculator online; it will probably be faster and you can also calculate EV values for ISOs other than 100.
The other way to use electric vehicles in the real world is to use the Sunny 16 rule. This rule states that, if the sun is looking good, set your aperture to f / 16 and your speed to Shutter for a correct exposure equal to 1 /[Your ISO], so in our case 1/100. If you look at the graph, you will see that f / 16 for 1 / 100th of a second has about one EV100 out of 15, which aligns perfectly with a sunny day. The fact is that you can then use it as a basis for setting the correct settings for other lighting situations. A slightly cloudy day needs f / 11 at the same shutter speed and ISO, just one more stop. A very cloudy day needs f / 8, a very cloudy day needs f / 5.6 and the light at sunset needs f / 4.
Although you should always review your photos to make sure you do not blowing your lights or crushing your shadowsIt's very good to be able to quickly guess the settings of the camera and be in the right stage.
One of the main reasons why people have trouble understanding the show is that they try to learn it in an abstract way. If you understand his relationship to the real world through exhibition values, it's a much simpler concept to understand.