Shutter speed

[rahuldg11]

Increasing or decreasing the shutter speed by one stop doubles or halves the amount of light reaching the sensor. How is this done in the camera? The same thing happens in aperture and I understand how that happens. i could explain it mathematically, but is that possible with shutter speed also?

[autofocus]

Originally Posted by rahuldg11

Increasing or decreasing the shutter speed by one stop doubles or halves the amount of light reaching the sensor. How is this done in the camera? The same thing happens in aperture and I understand how that happens. i could explain it mathematically, but is that possible with shutter speed also?

Picture the shutter as a curtain allowing light in...the slower the curtain is opened, the more time light will hit the sensor. Obviously, the opposite is true if you were to quickly open and close the curtain, less light hits the sensor.

[RichardTaylor]

The total light hiting the sensor is

(1) How much (aperture)
and
(2) For how long (shutter speed)

Another anology
The total amount of water coming out of a hose is;
(1) What is the diameter of the hose
and
(2) How long is the tap turned on?

[rahuldg11]

I understand this. What i wanted to know is: for aperture we know the f number is the ratio of the focal length and the diameter. From that i can mathematically establish that increasing or decreasing the f number by one stop, amount of light is doubled or halved. Is it possible to establish the same for shutter speed?

[zona5101]

??? shutter speed is even more directly "halves and doubles" without thinking about diameters and ratios and all...
30, 60, 125, 250, 500 etc represent:
1/30 sec 1/60 sec 1/125 sec...each of those is 1/2 as much or twice as much time as the next

[autofocus]

Like Zona said above the numbers are fractions of a second..so expressed as fractions 30 becomes 1/30th of second, 50 is 1/50th of a second, and so on...

[RichardTaylor]

The "equivalent" of 1 F stop
Half the time = half the light.
Double the time = double the light.

[rahuldg11]

Ok...now i get it...and what about ISO then? is it the same? Increasing the iso value implies doubling the sensitivity of the sensor? Is it like this?

[zona5101]

Originally Posted by rahuldg11

Ok...now i get it...and what about ISO then? is it the same? Increasing the iso value implies doubling the sensitivity of the sensor? Is it like this?

bingo.
100,200,400,800 iso are all one stop apart.