- The aperture regulates the lens opening - the wider it opens, the more light can enter
- The shutter-speed regulates the exposure. The longer the 'eye' is open, the more light gets in.
- The ISO-sensitivity sets the camera's light sensitivity. the more sensitive it is, the less light you need
So let's just put it wide open and to very sensitive, that should work right? wrong.
Every setting has certain 'side-effects', so it boils down to making compromises. Depending on what we want, we put the priority on of the above, and have to give in a bit on one or both of the other values. To get a better understanding, let's take a look at the settings, what ranges they have and what effects we can control:
|F-stop (Aperture)||1.4, 2.8, 4.0, 5.6, 8.0, 11, 16, 22, 32||Influences depth-of-field (blur/out-of-focus)|
|Shutter-speed||1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000||Influences motion freeze/blur|
|ISO-sensitivity||100, 200, 400, 800, 1600, 3200||high iso-speeds give more 'grainy' pictures|
Imagine a person standing in front of a house.
- with a large F-value (e.g. 2.8) we will see the person sharp and the house unsharp
- with a low F-value (e.g. 16) we will see sharp through the entire range
For portraits, photographers want to put the focus on a single person (shallow depth-of-field) - which means they prefer a large F-stop value. Your camera probably has a portrait-mode, in which it tries to do exactly this.
Imagine a helicopter with a rotating blade:
- with a fast shutter speed (e.g. 1/4000 second) it will appear to be standing completely still.
- with a slow shutter speed (e.g. 1/2 second) the rotor will be blurred
Your camera probably has a sports mode, in which it tries to freeze the action using a fast shutter-time.
The below overview gives you an impression of what ISO-value to set.
- 100-400 = bright summer day, outside
- 800-1600 = cloudy, afternoon
- 1600+ = evening, inside
If the image is to dark we can do the following:
- increase iso (more sensitive)
- increase aperture (open further)
- decrease shutter-speed (open longer)
The advantage is that they usually have really small F-stop values (smaller then 2.0) and are small and light. The disadvantage is that you probably need multiple for different focal lenghts (as such they can be inconvenient since you will have to swap lenses more often)
Now there is one thing to keep in mind - the minimum and maximum focal lenghts are given for full-frame camera's (the really expensive professional ones). The (pro)sumer models usually have a so called 'crop-factor'. For example the canon 550D has a cropfactor of 1.6.
If you multiply the focal length with this value, you get the corrected value. So a 70-200mm lens would be a 112-320mm lens on a camera with an 1.6 cropfactor. Notice that this is very nice for the maximum value (better zoom', but inconvenient for the minimum value (not as wide as on a full-frame dslr)
The below diagram shows what happens if you zoom between minimum and maximum focal lenght. Imagine the light-blue figure being your wide viewing angle. When zooming it moves towards the darker figure - and as such your angle gets smaller while at the same time increasing your 'range'.
The light-blue figure shows the minimum focal length and gives a wide angle.
The dark-blue figure shows the maximum focal lenght and gives a small angle.
The dashed lines show the in-between focal lenghts.
IS only helps countering your own motion - it essentially improves handheld images shot at slow shutter speeds. If you have a blurry image, and the foreground and background have the same level or blurr then your image was blurred due to camera-shake.
IS does little to help you capture motion (i.e. to freeze a moving object like wildlife, sports - without having motion blur). In this case a fast lens ( large aperture ) is the only way to freeze the speed, besides increasing the ISO sensitivity. Motion-blur causes only a (small) part of the image to be blurry (e.g. while making a picture of a landscape, someone walks sideways through the shot) By tracking the subject with your camera (i.e. keeping the car in the same spot, relative to the camera's viewpoint) you can keep the subject sharp while blurring the background.
Remote triggering of Canon speedlite's with the Canon ST-E2.
In general. flash (especially on-camera flash) has a very limited range. People photographing at concerts with flash (with the artist 30+ meters away) are - besides creating a lightshow - mostly wasting battery life.