What is a stop?
In photography, a stop is a measurement of Exposure.
If you were to increase the exposure by one stop – you would in effect be doubling the exposure.
So if your settings are
Shutter Speed: 1/100
And you upped the ISO value to 200 you will have effectively increased your exposure by 1 stop.
This function of photography can be a bit daunting but understanding this is instrumental in helping you achieve the results that you are after and knowing what needs to be done.
Let’s see a little simple sample of this.
Say you are shooting at f/2.8, 1/100 Shutter Speed with an ISO of 200 but the effect you are after is a shallower depth of field. Widening the aperture to f/2 will produce the required effect but knowing that this will double the amount of light that is entering your lens will allow you address this problem.
You’ve made a full stop with your aperture to get the correct DOF.
The consequence is that the exposure is too bright now.
To combat this you could halve the ISO to 100 or double the shutter speed to 1/200 of a second.
Each of the 3 elements will have different stops. Let’s see the difference between them.
ISO doubles between stops. So in effect:
ISO 100 -> ISO 200 is one stop.
ISO 200-> ISO 400 is one stop.
So far so good. Let’s move onto Shutter Speed stops
Shutter Speed Stops
The simple one here is when you are using shutter speeds of 1 second or longer. The same principle as above applies. You simply double the time 1->2, 2 -> 4 etc…
When shooting at fractions of a second (which will probably be most of the time at least during your early journey in photography) you will need to halve the number on the bottom (the denominator)
So 1/100 is twice the length of 1/200. 1 Stop, double the exposure.
1/50 is twice the length of 1/100. 1 Stop, double the exposure.
Phew… that wasn’t so bad. Now let’s move on to
This is where I’ll need you to bear with me.
This little puppy is the most complicated and mathematical of all.
The aperture scale doesn’t follow the same path as the shutter speed or ISO.
Aperture is measured in what is known as the f-stop scale. This f-number tells you how wide the aperture is which affects the exposure and the DOF. The lower the number, the wider the aperture (or bigger the hole).
The scale is as follows: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16 and f/22.
The most important thing to know about the numbers above when dealing with stops is that each number decreases the aperture to half its size (1 stop).
Keep in mind that the scale above does not show every number that will show in your camera. There will be other numbers in there (i.e.: 3.5 and 3.2) these are known as third stops and won’t be doubling of halving your exposure but lie somewhere in between.
Take out your camera, compose your shot and play around with the settings to see what the outcome is.
Compose? The next big factor in your photographic journey. Stay Tuned.