Speed / Aperture

Shutter Speed

The shutter is in the camera body, while it is open the light is entering into the camera.

The shutter speed is how long the shutter stays open when I shoot the camera and therefore the amount of time the light will be reaching to the sensor.

Higher speed: The less time the shutter is open, the less time the light is reaching to the sensor, that means in the same conditions that the sensor will capture less light.

Lower speed: The more time the shutter is open, the more time th elight is reaching to the sensor, that means in the same conditions that the sensor will capture more light.

I say in the same conditions because for each situation the light can be very different (we will see that later). The fact is that with the same shutter speed we could have too much light, just the right light or low light depending on the site and conditions. We must find the right shutter speed in each moment for the right exposure.

The correct exposure will depend on these 3 parameters, the shutter speed, the aperture and the ISO (we will see that later too). We must adjust these parameters in order to the sensor can capture the appropriate amount of light.

If I put a lower speed I increase the amount of light that the sensor will capture, on the contrary if I put a higher speed I decreased the amount of light.

Classic shutter speeds from less to more light:  

2” –1” –2 –4 –8 –15 –30 – 60 –125 –250 –500 –1000 –2000

1" means 2 second, 2" means 1 seconds. 2 means 1/2 seconds, 4 means 1/4...

60 (1/60 seconds) marks the limit  recommended for shoot without tripod, in lower speed we must use tripod.

Each change from one classic speed to the next is call one stop.

From one stop to the next:

If we go from less to more speed (example: from 15 to 30) we will have just the half of light capture for the sensor.

If we go from more to less spedd (example: from 15 to 8) we will have just twice of light capture for the sensor.

 How does it affect the shutter speed to the image?

We must understand that while the shutter is open the camera is capturing light but also is capturing everything that happens, all the movements,these movements will appear in the image.

The longer time the shutter is open more movements will be captured the camera, what is moving is going to be more blurred.

The less time the shutter is open less movements will be captured the camera, what is moving is going to be less blurred.

Here is a curious effect:

If I use a very very slow speed, things which are moving (people, animals, vehicles, ...) are very little time still in front of the camera in proportion to all the time that the camera his capturing the scene. What happen is: these objects, things or people will tend to become more blurred but also less visible with a lower and lower shutter speed. They  could even disappear completely to the image if I use a very very low speed.
 

Said and understood this, we will see what effects can be achieved with the shutter speed:

 Motion capture:

 Higher speed freezes motion.

Lower speed blur effect

The effect is only in moving objects

If all the image is blurred we made the wrong photo, in this case we didn´t cause the effect by using the shutter speed but because we move the camera.

Aperture

The lenses have a diaphragm, this is like a curtain that we can open or close more or less around the lens. It makes more or less light can pass through the lens because.

If we open the aperture tha gap through light enters is greater (more light) and if we closed it the gap is smaller (less light).

The diaphragm is inside the lens, that means depending on the lens that we use we will have different apertures.

There are lenses more or less bright, the more bright it is the maximun aperture it have.

We measure aperture with the f-numbers.

In this case for example the maximum aperture in this lens  is f/2 and the minimum aperture is f/22.

Logically each lens will have a maximum aperture and then we can go close it. We can see  the maximum aperture in the front of the lens, this corresponds to the lowest f-number.

The lens always indicate us the minimum number f we can get, so for example in this lens we have 1:1.8, that means our maximum aperture will be f/1.8.

Note that the maximum aperture is the minimun f-number. When I start closing the aperture the f-number is going higher.

In zoom lenses we have two f-numbers in the front, for example: 1:3.6-5.6, the first number is the maximun aperture corresponding to the shortest focal length and the second for the longest.
The more brighter the lens is the more expensive, lenses that allow a full opening of f/1.2 are very bright and very expensive, and it's very rare that even in a professional level we have lenses that allow more aperture.

Lower f-number ==> higher aperture

Higher f-number ==> lower aperture

Classic apertures:      

1 – 1.4 -2 – 2.8 – 4 – 5.6 – 8 – 11 – 16 -22

Each change from one to the next is also one stop, and it means the same, if we open aperture (for example from 4 to 2.8) we will have twice amount of light, if we close aperture (for example from 4 to 5.6) we will have half amount of light.

How does it affect the aperture to the image?

In the depth of field:

The blur affects both the back and the front

The higher f-number the more focused the background. If I want to blur the background I must use a lower f-number.

Brighter lenses - smaller f-number - have more effect of blurring the background.

The sharpness:

 

The higher f-number the greater shoud be the sharpness, but sharpness also depends on the diffraction which increases with higher f-numbers.

As a result of that it is considered that the greater sharpness is achieved when the aperture is one or two steps more open than the maximum of the objective.

For example if  we have 1:2 maximum aperture f/2, then the sharpness probably will between  f/4 and  f/8.

Interaction between shutter speed and aperture:

We have stops, when I go up one classic stop in the camera the amount of light falls to half, when I go down one classic stop the amount of light rises to the double.

I can up or down stops with aperture or shutter speed (and also with the ISO) and the result is the same if I do it with aperture or shutter speed ( or also with the ISO ).

Let´s see that I want more light, then I can do two things ( but for now we only talk about aperture and shutter speed ):

- I can open the aperture: I can lower the f-number.

- I can lower the shutter speed.

¿ When I do the first and when I do the second ?

If I have a correct exposure and I want to achieve freezes motion then I have to raise the speed and I can compensate the loss of light opening the aperture (lower f-number).

If I have a correct exposure and I want to achieve depth of field then I have to close aperture (higher f-number) and I can compensate the loss of light down the shutter speed.

...

APERTURE

Maximize depth of field: For large depth of field we need the minimum aperture.

Selective focus: To highlight an object leaving the rest out of focus I need the maximum aperture.

SHUTTER

Higher speed: Under 125 (1/125) I can freeze motion.

Lower speed:  Motion capture.

Panning:   I use  lower shutter speed and when I shoot I follow the moving object. The result is a blurred background and the subject frozen.

Silk effect: +4”  the water becomes in lines +20” water becomes in mist-foam +2 minutes the water becomes transparent like a fog.

Painting with light: Lower shutter speed and moving objects with light.

Please note:
Bright lenses enable lower ISO speeds which means less noise and better image quality.

Bright lenses also allow faster shutter speeds in dark situations.