Thank You @AJHenderson. thats what I mean..

@primitiveType cool, did the answers on that question help you?

Yeah not really But they have me an idea

I have some lame doubts of this Shallow depth of field (Object will be in Focus and background will be blured)

For example in my PIC There tow people in it So what I want here is blur the back ground and keep them in focus

BUt in D5200 I cant focus like that..

I use AF Area focus

I can manage to get them into focus but that shallow depth of feild is missing

I cant fully blur the background

why wide aperture is shallow depth of field ?

@primitiveType that's just the way optics work

basically, light has to be coming in from the sides in order to spread back out more quickly

with a narrow aperture, light can't spread out as quick, so it can't blur as much

with a wider aperture it can

similar thing for full frame cameras versus crop. Since full frame sensors are farther away from the aperture, the light has more time to spread out as it expands to fill the sensor, where as on crop sensors, it doesn't have as much time to spread out

the fact is, with a kit lens and a crop body, you are going to have a hard time getting background blur

it is doable, but you have to position the subjects, background and camera carefully (as described in the answers to that question I linked)

@AJHenderson Thank you very much for your response .. So To blur the background we need to allow more list righ?

Am I correct regarding for this equation LongExposer+narrow Apparture = HighShutterSpeed+wideApparture

No, the amount of light only impacts exposure.only the aperture and the focal distance impact depth of field

However if you use a wider aperture (smaller f number), you will need a faster shutter speed to avoid overexposure

Alternately, iso can also be adjusted

For exposure

That's called the exposure triangle, but as I previously mentioned, exposure and depth of field are not related,other than your desired dof may set your aperture to a fixed value

Oh Okay okay Thank you so much