TWO QUESTIONS :)

[shankooty]

I have two questions:

1) why most photographers use a wireless flash trigger unit although their cams have a built-in commander unit in the pop-up flash? is that because there are some limitations for this built-in unit?

2) concerning the Nikon d5100 limitations, a) no built-in commander unit; you can buy cheap Chinese wireless flash trigger.. b) no built-in motor, now nearly all Nikon lenses have motors c) no manual control on video mode.. you can work around it by locking the exposure (search youtube) ....regarding these all factors, why people still talking about these problems anyway in the d5100? i think they are not being problems anyway...i wish someone how is already using this camera shares his experience with it..

 

[Big Mike]

1) why most photographers use a wireless flash trigger unit although their cams have a built-in commander unit in the pop-up flash? is that because there are some limitations for this built-in unit?

There certainly are limitations when using a flash to communicate to the remote unit. Firstly, if you're not in a small encloses space, you will need line of site between the commander flash and the remote's receiver. Secondly, in bright lighting conditions (especially out in the sun) the communication can be spotty at best).
Many photographers find that radio triggers are more versatile and more reliable.