Exposure chart

What would happen if you set the camera like this: ISO 100 - f/32 - 1/8000sec?

If you are an experienced photographer, you will answer that probably  if you use this combination you will get an underexposed picture.

But for beginners, it is not always easy. So, I made the following chart:

The difference between each number is one stop. You can print it and consult it, every time you want to set your camera.

The Helios Exposure Value Chart

OK. You understood what f/number is, what ISO is and what shutter speed is. Also, you can use ND filters occasionally. But when you have to find an equivalent combination between shutter speed - aperture - ISO it is not easy for you.
With this chart it is! It gives you choices among the various aperture–speed-ISO-ND filter combinations that result in the same exposure. The only thing you have to do is add the helios that match each value to find the total. Then, every same total will give you an equivalent combination.
Let's see an example: All of us know the famous "Sunny 16 rule". According to this rule in a sunny day we can use the following values: Aperture f/16 - Shuter speed 1/125 sec - ISO 100. At the Helios Exposure Value Chart these values lead to a total of 16 (4 for f/16 + 9 for 1/125 sec + 3 for ISO 100). Every total 16 leads to an equivalent combination (the same amount of light). So, if we choose f/4 - 1/4000 sec - ISO 200 (8 for f/4 + 4 for 1/4000 sec + 4 for ISO 200) the total will be again 16.
If you want, for example, to photograph waterfalls and you need a slow shutter speed in order to produce the classic blurred effect you can use a ND1000 filter. In that occasion you have to subtract 10 selenes so you can achieve the 16 helios in such a way: 8 for f/4 + 14 for 1/4 sec + 4 for ISO 200 -10 for ND 1000 (total 16).
It is simple, isn't it?

Αperture

When a photographer says that he took a shot with f/5.6, he states about the amount of light that will pass through the aperture diaphragm, not about the size of the hole (entrance pupil). The same entrance pupil’s size does not implies that will pass the same amount of light if we refer to different focal length lenses. So, in order to could compare the amount of light in all lenses, we use the f/number which is a value that expresses the relative aperture.
See at below photo in order to understand better:

In this picture, I photographed, in one shot, 3 of my old, manual focus, lenses at the same aperture  f/5.6. As you can easily see, the diameter of the entrance pupil is different in each lens, but the aperture is the same, it is f/5.6. So, although the size of the hole is different in all 3 lenses, the amount of the light that will pass through is exactly the same.
In the above photo you can measure the diameter of the entrance pupil with the help of the meter: 4.3 mm for 24mm, 8.9mm for 50mm and 24.1mm for 135mm lens. Right?
Now, you can calculate the f/number by this equation: N = f/D, where N is f-number, f is focal length, and D is entrance pupil diameter.
In our example:
24/4.3= 5.6
50/8.9=5.6
135/24.1=5.6
Amazing? No, it’s only mathematics and physics!