Turnerea
TPF Noob!
- Joined
- Aug 28, 2008
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- 212
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- SoCal
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I've read some of the beginning photo books, done a good amount of searching online- I understand all the basic concepts of aperture, shutter speed, ISO to get a proper exposure.
I'm just confused as to why aperture is expressed as a fraction. I understand how the stop system works to increase/decrease the area by 2, but for different focal lengths, I don't understand why the same f number corresponds to the same amount of light (assume the same shutter speed).
For Example
If you had f/1.8 on a 55mm lens, wouldn't that equate to more light into the sensor than f/1.8 on a 24mm lens? The actual diameter of the opening for the 55mm lens is 55/1.8=30.5mm, while for the 24mm lens it is 24/1.8=13.3mm, right? Now the area just scales linearly, so the areas are different... maybe I'm missing a concept here??
Hopefully that makes sense, and someone might have a suggestion for another way of thinking about it that might help myself and others who might have questions along the same lines....
I'm just confused as to why aperture is expressed as a fraction. I understand how the stop system works to increase/decrease the area by 2, but for different focal lengths, I don't understand why the same f number corresponds to the same amount of light (assume the same shutter speed).
For Example
If you had f/1.8 on a 55mm lens, wouldn't that equate to more light into the sensor than f/1.8 on a 24mm lens? The actual diameter of the opening for the 55mm lens is 55/1.8=30.5mm, while for the 24mm lens it is 24/1.8=13.3mm, right? Now the area just scales linearly, so the areas are different... maybe I'm missing a concept here??
Hopefully that makes sense, and someone might have a suggestion for another way of thinking about it that might help myself and others who might have questions along the same lines....