Diaphragm is a parts like a donut between the lens and the shutter, Adjusting the size of the hole in the center of diaphragm adjust the amount of light hitting the image sensor. The diaphragm is expressed as the F-number such as F1.4, F2, F2.8, F4, F5.6, F8, F11, F16, F22. As the F-number goes up, the hole at the center becomes smaller, and the light passing through the lens becomes narrower, so the picture becomes darker. If you lower the F-number, the hole become larger and the light passing through the lens will be wider, so the picture will become brighter.
The diaphragm has another effect. It is the depth of field explained in focus. Increasing the F-number increases the depth of field, and lowering the F-number decreases the depth of field.
How to decide shutter speed and diaphragm
Based on the above, let’s organize how to decide the diaphragm and shutter speed. First of all, once you decide the angle and the area to display, focus on what you want to display most clearly. Then adjust the diaphragm and decide the brightness of the photo.
Next, consider the range depth of field b>. Please compare the two images below.
A has a shallow depth of field, so only the lion is clearly visible. People watching the photos may think that they are “cute” or “cool” when looking at the lion. There is something behind, but you will not get much attention.
B clearly shows up to the zebra behind. because the depth of field is deep. People watching the pictures will see the lion, but also pay attention to the zebra that is behind. People maybe think “Do not you notice the lion in the back zebra?” or “I wonder what the zebra feels like”.
Like this, The depth of field affects the impression of photos. The most important thing is where you want to show to the people in the scene.
If you want to show clearly to the back of the screen, set lower the F-number and deepen the depth of field. But,photo will become brighter, so speed up the shutter speed accordingly, shorten the time light enters, and adjust to the first brightness you set.
On the contrary, if you want to show only lion, set higher the F-number. And the photo becomes darker. So, slow down the shutter speed and lengthen the time light enters.
In this way, you can decide the focus, diaphragm and shutter speed.
Digital cameras record images by converting light impinging on image sensor into electrical signals. The shutter speed and diaphragm adjust the brightness of the photo by changing the amount of light hitting the image sensor, but the ISO is a function that can change the brightness of the photo by amplifying the electric signal. For example, if you try to shoot fast moving objects in dark places, you set shutter speed to slow, but the photo will be blurred, but if you increasing the ISO, not set slow the shutter speed, you can take a bright picture without blurring. However, there are disadvantages that the photograph becomes grainy and noise increases when ISO is raised. In case of stop motion animation, Since the puppet does not move, there is no worry that the photo will be blurred. I think that it is safe to set the ISO as low as possible because it can handle the shutter speed sufficiently without raising the ISO sensitivity.