Rahul...these are the basics:
Exposure depends on these factors :
1. Aperture Value (how much light is allowed through your lens).
2. Shutter Speed (how long the sensor is exposed to this light coming thru the lens)
3. ISO speed (how sensitive is your sensor to the light falling on it.
A > When you use Av mode (Aperture priority) you get to decide
a) The aperture value...like F2.8, F3.5 F8 and
b) The ISO speed 100/200/400/800 etc..
c) Setting the right desired exposure (your light meter would point
from -2....-1....0...+1...+2) epending on how you set it.
The Camera's metering system tells the camera how much shutter speed is required to achieve the desired exposure (your light meter would point from -2....-1....0...+1...+2).
d) The camera gets to choose the resultant shutter speed like 1/30, 1/60/1200 etc
B > When you use Tv mode (Shutter speed priority) you get to decide
a) The shutter speed value like 1/60, 1/100 1/125
b) The ISO speed 100/200/400/800 etc..
c) Setting the right desired exposure (your light meter would point
from -2....-1....0...+1...+2) epending on how you set it.
The Camera's metering system tells the camera how much shutter speed is required to achieve the desired exposure (your light meter would point from -2....-1....0...+1...+2).
d) The camera gets to choose the resultant Aperture width for teh chose ISO, speed and desired exposure values.
D > When you use M mode (Manual) you get to decide :
a) The shutter speed value like 1/60, 1/100 1/125
b) The ISO speed 100/200/400/800 etc..
e) The aperture width.
The camera derives the resultant exposure and tells you how wellunder/over exposed your image is.
Hope this helps...
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