Understanding the relationship between, shutter speed, aperture, ISO,and focal length

I have been spending some time looking at the relationship between shutter speed, aperture and focal length. After watching a video by digital Rev on how to shoot photography in the early morning with little light I decided to explore more about how to get the best shots with different lenses, one of the main things I discovered was the best relationship between the focal length of the lens and the best setting to shoot with on the shutter speed for example of shooting on a 50mm lens its best to shoot at a shutter speed above 50 for example 1/60th and if shooting on a 200mm lens above 1/250th to avoid camera shake. The website explains that if shooting on a 50mm lens it’s important not to shoot below 1/60th to avoid camera shake. Another good thing to website explained was how moving the shutter speed up or down effectively doubles or half’s the amount of light let as does the aperture so a good tool to use is if increasing the speed of the shutter speed to also increase the aperture by one stop also to compensate for it in lighting. Or alternatively increase the ISO the following is taken from the website as examples to consider

For example if you speed up your shutter speed one stop (for example from 1/125th to 1/250th) you’re effectively letting half as much light into your camera. To compensate for this you’ll probably need to increase your aperture one stop (for example from f16 to f11). The other alternative would be to choose a faster ISO rating (you might want to move from ISO 100 to ISO 400 for example).

 Read more: http://digital-photography-school.com/shutter-speed#ixzz2I3pXFCXS

 I’ve found this very useful and although not directly linked to filmmaking I know and feel that the greater knowledge of how cameras work in a general sense the greater understanding i can take into filming a piece. Also as a general point i also want to understand how to be a competent photographer as well as filmmaker as this is another interest and passion of mine and also think it will prove a greater help in becoming a more accomplished cinematographer by having a greater understanding of lenses, light, shutter speed, aperture,ISO and relationship between them all.