i don’t get it.
In: Physics
ISO is how sensitive the sensor would be to light. It used to be ASA before. It’s called ISO due to the International Organization of Standardization making the value universal.
Diaphragm is a set of shutters allowing light to pass. They can open and close. It also makes things sharper or blurry. Giving you Bokeh effect.
Think of iso as the sensitivity of a microphone. If you increase it, it can pick smaller sounds but also background noise.
Diaphragm is just a adjustable hole in the lens to allow more or less light. It also affects depth of field.
When taking a landscape photography you want the maximum of the landscape to be sharp, so you increase the F stop number, which make the diaphragme hole smaller. Undesirable effect is that you have less light (issue with night landscapes).
When shooting portrait you generally want a soft background to focus the viewer into the face. You reduce the F stop number, which increases the diameter of the hole in the diaphragm. More light enters and the depth of field is reduced.
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