A STOP (step) is a comparison unit, and always in a dual relationship (Positive) and half (negative) in some manuals is also called the EV (Exposure Value).
I mean, if I gain a stop (+1 stop), I doubled what I had, and if a rest stop (-1 stop), I'm halving he had.
STOP in photography is used to express both the increase and decrease of light with which we will make the exposure.
Thus, if we increase +2 stops, we have increased the light reaching our sensor in 4 times, and if we decrease -3 stops, we have removed 8 times the light to the sensor of your camera ... you understand?
Let's see, +2 stops is the same as +1 first increasing and then +1 again ... right?, Ok!, then by increasing the first stop we have doubled the amount of light and then by increasing the second stop will be duplicating what has already been doubled, this is how we will have 4 times more light than the beginning, and if additional stop aumentásemos +1, double what has already quadrupled, ie 8 times would increase the light reaching the sensor.
Similarly, by decreasing -1 stop light will be decreased by half, and if we subtract -1 additional stop, we will have 1 / 4 of the original light (half of half), and finally, to take - 1 stop, we will have one-eighth of the original light (half of a quarter). Since
A STOP or EV is an increase or decrease a little thick, it is common that do allow cameras in increments of one third, +1 / 3 = +0.3 - 2 / 3 = -0.7 for example. I hope I have illustrated
somehow the meaning of STOP in photography. Now go to your camera and look for a button or an item from a menu that has a square with a + and - (positive and negative) on the inside, this is the control for exposure compensation, showing a scale of STOP's or EV's where the right side is positive and the negative left ...
compensation function
EV = Exposure Value
Once you have located the symbol, I recommend you go to your camera's manual and read a little of what the manufacturer says about the use of that function. As the trigger, or press the corresponding button, you'll see the scale below.
Form interpret the scale of compensation
Since a STOP or a EV is an abrupt change something, you can usually make gains both positive and negative STOP or EV-THIRDS OF for better control. So one can perform increases 0.3 0.7 1.0 1.3 1.7 2.0 2.3 .... stops, and the way to the downside.
odem In the following example are seen as three pictures, first send the meter such as the chamber, the second photo with a stop less, ie half as much light as the first, and finally the third photo with a stop more than the first, ie twice as much light.
Photo
odem In the following example are seen as three pictures, first send the meter such as the chamber, the second photo with a stop less, ie half as much light as the first, and finally the third photo with a stop more than the first, ie twice as much light.
original picture without compensation, as measured
photometer camera.
Stop Photo offset to -1,
has half the original light.
Photo offset to +1 stop,
has twice as much light as the original.
This is what makes Olympus manual for an E3 in respect of compensation:
For an alternative explanation, click here
And all this ... that I use?
serves as the basis for understanding the mechanisms of sound exposure, which constitutes one of the principles of photography that should be understood by all those who wish to leave auto mode and move their cameras to take control of your photographs.
Correct Exposure:
is the result of some actions, which aims to ensure that the sensitive element of the camera (sensor or film), as applicable, be exposed to the amount of light to achieve a correct picture from the perspective of amount of light that is not underexposed (too dark) or overexposed (too bright), just at the correct exposure.
Measurement of light (where it all begins):
To achieve the objective we correct exposure from a good measurement of light, it is responsible photometer, which may be the one built into the camera (every digital camera has a built-in light meter), which measures the light reflected towards the camera, or for better control can use an external photometer, which has the ability to measure incident light in the scene and / or subject. At the moment we are left with the meter built (ovbiamente more advanced cameras, and expensive, have more sophisticated photometers).
In most digital cameras there are three light metering modes (light metering), or whatever it is, we can tell the meter how we want to measure the light in our scene.
Click to enlarge
1 .- Measurement Matrix:
In this mode, the meter divides the entire scene in the frame we have in many areas small and light measured independently for each of these areas, then taking an average figure trying to ensure that most of the framed scene has the measure of light that corresponds, in this processor intervenes assessment the camera, and therefore also called evaluative metering, this is a good way for landscapes and more.
2 .- Central Weighing Measurement:
is basically a system very similar to the matrix, but when evaluating the lighting scene gives more weight to the central area of \u200b\u200bthe scene, is a way for portraits, for example, or when shooting scenes where the point of interest is at the center of the frame.
3 .- Measurement Spot:
In this mode the meter only measures the light in a small area at the center of the frame, this method of measurement is used for scenes with complex lighting, high contrast etc. is more work to master, but once achieved is the one that will give us satisfaction. It all depends on where it says a central point to take the sample of light. Look at the example below, where I took a picture of a focus on putting the measuring point on the bulb itself, for the camera to calculate the parameters of making and thus ensure detail despite the very light ... get tested!.
corect To achieve an exhibition should properly handle three parameters:
.- The shutter speed (time).
.- The aperture (numbers "f").
.- The ISO (sensitivity).
The first two control the amount of light reaching the sensor or film in our camera, the shutter speed makes controlling the time the shutter (gate that lets light enter), remains open, this can be from a very short time (high speed) how 1 / 4000 of a second (a second-cuatromilavo) until a very long time as 30 seconds, while the aperture makes controlling the size of the opening through which light will enter, this can range from very large apertures (f: 1.4), even very small openings (f: 22). Finally, the ISO operates electronically amplifying the light that reaches the sensor, the product of the combination of speed and aperture determined by the photometer.
Shutter Speed \u200b\u200b(Shutter Speed):
This parameter controls the time the curtains are open to let light into the sensor or film, as the case, is measured primarily in fractions of a second, standardized steps with a caesarean relationship STOP units or EV.
Click to enlarge
Suppose we choose, just by way of example, the speed of 1 / 125 of a second (a second-cientoventicincoavo) as a starting point, and We agree with the "0" scale on the chart above, if we double the amount of light with this single parameter, ie increasing one stop (+1 STOP), then we should double the time, and this will be 1 / 60 sec., but if we decide to take a picture with one-eighth of the light we had with 1/125 seg., entonces deberemos restar -3 STOPS; o lo que es lo mismo, poner la velocidad de obturación en 1/1000 seg. (un milésimo de segundo).
Es así cómo este solo parámetro de la velocidad de obturación me permite controlar, mediante el tiempo, la cantidad de luz que entra al sensor de mi cámara; obviamente tambien tenemos medidas intermedias para poder realizar saltos de un tercio de STOP ó EV, para con control más fino, a continuación les muestro algunos valores intermedios (tercios de STOP) hacia las velocidades más rápidas que 1/125 seg. (en negro):
1/125 - 1/160 - 1/200 - 1/250 - 1 / 320 - 1 / 400 - 1 / 500 - 1 / 640 - 1 / 800 - 1 / 1000
And now some intermediate (STOP-thirds) to slower speeds:
1 / 15 - 1 / 20 - 1 / 25 - 1 / 30 - 1 / 40 - 1 / 50 - 1 / 60 - 1 / 80 -1/100 - 1 / 125
aperture (Aperture) and numbers f:
diaphragm iris camera or Pulilan equivalent to the eye (the black center part), the which opens and closes automatically according to the amount of ambient light.
The size of this opening, in cameras, is represented by a number (f-), which results from dividing the focal length of the diameter of the lens, ie is a certain relationship between the two measures.
But now want to go into technicalities, since the purpose of this post is to unravel the mysteries of the STOP or EV, so for now I have to trust me and believe what I describe in the following paragraphs.
In the case of the aperture, the smaller numbers represent larger openings, and values \u200b\u200bsuch as 1 - 1.4 - 2 - 2.8 represent respectable opening, the former being characteristic of very expensive glasses, and securities how 16 - 22 to 32 represent very small openings.
I will choose an intermediate aperture, f: 8, to place at the center of the scale, so we will see how to reduce the aperture (high numbers), we reduce the entry of light into our sensor and if we use larger apertures (low numbers), we allow the entry of more light into our sensor, and obviously be interpreted in units estopuede STOP or EV, for a better understanding of what we are doing.
Click to enlarge
This parameter can also be manipulated into thirds to stop for a finer control, so we have the following intermediate (stop-thirds) For smaller openings af: 8 (in black):
8 - 9 - 10 - 11 -13 to 14 - 16 - 18 - 20 - 22
And these are the values intermediate (stop-thirds) for openings greater af: 8:
2.8 - 3.3 - 3.5 - 4 - 4.5 - 5 - 5.6 - 6.3 - 7.1 - 8
For an alternative explanation Engadget PHOTO click here
value ISO (sensitivity / gain):
Unlike the two previous standards, the ISO does not act on the entry of light into the sensor or film, but on the sensitivity, in the case of the film, or Amplification of the electrical signals in the case of the sensor. Consider the first case
This value represents feeling in a movie, so that a film with ISO 800 name is more sensitive than +3 STOPS denominació one with ISO 100, which translated into simpler language, means that it requires eight times less light to take the same photo ... means that it is good to take photos and films of low light situations (churches, interiors etc.) similarly, an ISO 50 film is -1 STOP less sensitive than an ISO 100, ie needs twice light to take a picture equivalent.
For the sensor, ISO value represents the amount of amplification that we apply on the electrical signals who came to that component, so if I apply a value ISO 200, I doubled the amplification if compared with that applied to ISO 100. It is understood that this case relates to digital cameras, so how in low light conditions we have the resources to raise the ISO setting on our cameras, this makes the effect that there is more light than actually exist, we gives the possibility to take photos in low light ... but at a price, photos taken with high ISO values \u200b\u200bhave less quality than low ISO vaores.
pubic But I have a post about it, enter the following link to access it:
ISO value
With this information, zero have exhausted the subject of STOP, in a next post I will explain the close interrelationship between these three parameters: shutter speed, the apertuta the diaphragm and the ISO. In the meantime I recommend you come to this link (in English) which they can go forward an idea:
The SimCam
If you think that some concept is not clear, please write to blog let me know.
... Continued ...
Until NEXT post!
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