Here is another learning series article and video. This time I go over the camera lens aperture.
The camera lens aperture is the variable opening inside the lens that lets more or less light into the camera. A small aperture has a larger number.
See a full technical description of aperture on Wikipedia:
http://en.wikipedia.org/wiki/Aperture
Also important is the f-number that explains what the aperture number means:
http://en.wikipedia.org/wiki/F-number
f-number = focal length / diameter of the entrance pupil
So if we want to know the entrance pupil size of an 100mm f4 lens we calculate it like this:
Diameter = 100 / 4
Giving us a 25mm front lens element.
An 85mm f1.4 lens results in a 60.7mm front lens element (85 / 1.4 = 60.7143).
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| Aperture size vs. depth of field. |
The most important statement I didn’t cover in the video is “the aperture determines how collimated the admitted rays are,” so a small aperture has very collimated rays of light getting through to the camera’s sensor.
A large aperture (f1.4) will give you less depth of field (distance of perceived sharpness), and a smaller aperture (f22) will give you a larger depth of field.