benjiblanco
09-06-2009, 11:19 PM
To take a photo, you need to get the correct amount of light from the subject through the lens into the camera, onto the sensor.
The settings you can control on your camera to make sure it gets the correct amount of light are..
The Aperture, How big will the aperture be, the hole the light travels through to reach the sensor.
The Shutter Speed. How quick will the shutter open and close, allowing the light to pass through to the sensor.
The sensitivity of the sensor or film. When the light reaches the sensor, how sensitive is the sensor to light, does it need a lot of light to expose properly, or does it need a really small amount of light to expose correctly.
Aperture is measured in f numbers, a small f number, ie f4 is a big aperture. a large f number, ie f16 is a small aperture.
Shutter Speed is measured in seconds. 1/10th of a second is quite slow, 1/2000th of a second is pretty fast.
Sensitivity of the sensor or film is measured in ISO, ISO 100 being not very sensitive. ISO 1600 being very sensitive.
What these setting are will depend on how light the subject is, how much you want in focus and if any of the subject is moving, or indeed if you are moving (camera shake).
Depth Of Field - DOF - is how much of the image is in focus. A large DOF will mean everything from an object very close to you, and an object very far away from you is in focus. A shallow DOF means that the object you focus on is in focus, but any objects closer or further away, will be out of focus.
When taking a picture, we have to analyse what we are photographing, decide how much light there is, how much of the image do we want in focus, are there any fast moving objects we want to capture, are we ourselves moving (camera shake) or are we using a tripod.
When we have decided that, we can then make the decision on what settings to use.
If we want a large DOF (lots in focus), we need to use a small aperture, a larger f number, eg f16
If we want a shallow DOF (not much in focus) we need to use a large aperture, a small f number eg f4
If we want to freeze any motion, or to avoid camera shake, we need to use a fast shutter speed, 1/60th or faster.
If we want to show motion in our pics, or there is no movement in the subject and we are using a tripod, we could use a slow shutter speed. 1/60th or slower.
If we want a large DOF AND a fast shutter speed, we may not get enough light passing through to the sensor, we then may have to make the sensitivity of the sensor higher to compensate, ie a higher ISO, eg ISO 800 or more.
When we change any of these settings, we usually do it by doubling or halving. (known as a 'stop')
We make the aperture twice as big, or half as big, we make the shutter twice as fast, or twice as slow, we make the iso twice as sensitive or half as sensitive.
Doubling or halving Apertures. Aperture is the area of a circle, an measured as a fraction, so the numbers are a little tricky to start with.
f1, f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22, f32, f45.
Thes f numbers are reducing the size of the aperture by half each time.
http://i3.photobucket.com/albums/y70/munchycarrot/Picture2-2.png
Going back to the start, we need to make sure the Correct amount of light passes through to the sensor, and the sensor has the right sensitivity for that amount of light.
When we (or the camera) get the settings right for the correct amount of light, we can then change any of one the three settings, as long as we adjust one or both of the other 2, to compensate. We do this by halving of doubling the settings.
For example.
A Landscape on a bright sunny day. The correct amount of light needed may produce these settings.
ISO Shutter Speed Aperture
200 1/200th f8 = correct exposure
If i then half or double any of these settings i need to half or double one of the other settings to compensate.
ISO Shutter Speed Aperture = correct exposure.
100 1/100th f8 = (halved iso, so doubled shutter speed)
100 1/200th f5.6 = (halved shutter speed, so doubled aperture)
200 1/400th f5.6 = (doubled iso, so halved shutter speed)
200 1/200th f8 = (doubled shutter speed, so halved aperture)
400 1/200th f11 = (doubled iso, so halved aperture)
All of these will produce a picture with the correct exposure.
In Aperture priority, we get choose the aperture we want, and the camera will calculate the shutter speed for us.
In Shutter Priority, we get to choose the shutter speed and the camera will calculate the aperture size for us.
Iso is usually best to set as low as possible, ie 100 or 200. If set at 1600, the result can be unwanted noise (tiny dots like film grain) in the shot. Sometimes this is unavoidable.
If the shutter speed is too slow for us to hand hold the camera without introducing camera shake, and we need a particular aperture to get a large enough DOF, then we have no alternative but to increase the iso, the result of this will be we can then use a faster shutter speed and still get a correct exposure.
The settings you can control on your camera to make sure it gets the correct amount of light are..
The Aperture, How big will the aperture be, the hole the light travels through to reach the sensor.
The Shutter Speed. How quick will the shutter open and close, allowing the light to pass through to the sensor.
The sensitivity of the sensor or film. When the light reaches the sensor, how sensitive is the sensor to light, does it need a lot of light to expose properly, or does it need a really small amount of light to expose correctly.
Aperture is measured in f numbers, a small f number, ie f4 is a big aperture. a large f number, ie f16 is a small aperture.
Shutter Speed is measured in seconds. 1/10th of a second is quite slow, 1/2000th of a second is pretty fast.
Sensitivity of the sensor or film is measured in ISO, ISO 100 being not very sensitive. ISO 1600 being very sensitive.
What these setting are will depend on how light the subject is, how much you want in focus and if any of the subject is moving, or indeed if you are moving (camera shake).
Depth Of Field - DOF - is how much of the image is in focus. A large DOF will mean everything from an object very close to you, and an object very far away from you is in focus. A shallow DOF means that the object you focus on is in focus, but any objects closer or further away, will be out of focus.
When taking a picture, we have to analyse what we are photographing, decide how much light there is, how much of the image do we want in focus, are there any fast moving objects we want to capture, are we ourselves moving (camera shake) or are we using a tripod.
When we have decided that, we can then make the decision on what settings to use.
If we want a large DOF (lots in focus), we need to use a small aperture, a larger f number, eg f16
If we want a shallow DOF (not much in focus) we need to use a large aperture, a small f number eg f4
If we want to freeze any motion, or to avoid camera shake, we need to use a fast shutter speed, 1/60th or faster.
If we want to show motion in our pics, or there is no movement in the subject and we are using a tripod, we could use a slow shutter speed. 1/60th or slower.
If we want a large DOF AND a fast shutter speed, we may not get enough light passing through to the sensor, we then may have to make the sensitivity of the sensor higher to compensate, ie a higher ISO, eg ISO 800 or more.
When we change any of these settings, we usually do it by doubling or halving. (known as a 'stop')
We make the aperture twice as big, or half as big, we make the shutter twice as fast, or twice as slow, we make the iso twice as sensitive or half as sensitive.
Doubling or halving Apertures. Aperture is the area of a circle, an measured as a fraction, so the numbers are a little tricky to start with.
f1, f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22, f32, f45.
Thes f numbers are reducing the size of the aperture by half each time.
http://i3.photobucket.com/albums/y70/munchycarrot/Picture2-2.png
Going back to the start, we need to make sure the Correct amount of light passes through to the sensor, and the sensor has the right sensitivity for that amount of light.
When we (or the camera) get the settings right for the correct amount of light, we can then change any of one the three settings, as long as we adjust one or both of the other 2, to compensate. We do this by halving of doubling the settings.
For example.
A Landscape on a bright sunny day. The correct amount of light needed may produce these settings.
ISO Shutter Speed Aperture
200 1/200th f8 = correct exposure
If i then half or double any of these settings i need to half or double one of the other settings to compensate.
ISO Shutter Speed Aperture = correct exposure.
100 1/100th f8 = (halved iso, so doubled shutter speed)
100 1/200th f5.6 = (halved shutter speed, so doubled aperture)
200 1/400th f5.6 = (doubled iso, so halved shutter speed)
200 1/200th f8 = (doubled shutter speed, so halved aperture)
400 1/200th f11 = (doubled iso, so halved aperture)
All of these will produce a picture with the correct exposure.
In Aperture priority, we get choose the aperture we want, and the camera will calculate the shutter speed for us.
In Shutter Priority, we get to choose the shutter speed and the camera will calculate the aperture size for us.
Iso is usually best to set as low as possible, ie 100 or 200. If set at 1600, the result can be unwanted noise (tiny dots like film grain) in the shot. Sometimes this is unavoidable.
If the shutter speed is too slow for us to hand hold the camera without introducing camera shake, and we need a particular aperture to get a large enough DOF, then we have no alternative but to increase the iso, the result of this will be we can then use a faster shutter speed and still get a correct exposure.