D3100

zaid

How i can use d3100 in manual mode effectively. ?

bruto

That's a big subject and the question is too general to answer very usefully. First off I think would be say what you're using now, and what your goal is. Switching from one of the automated modes to either P,S,A or M modes will give you the ability to control many functions of the camera that Auto and other modes take over.

But what is most effective will depend a lot on what you are trying to accomplish and what improvements you would like to see.

One of the advantages of such things as the "cheat sheets" offered by the host of this site is that they can provide settings that will utilize those modes, without requiring you to experiment right away. Once you've gotten used to how they work, and what happens when you vary them a little, you can gain power over your exposures, varying things as you see fit. Various other resources can be found on the net as well, but settings that are particular to your camera can help, since you can be sure that what they call for actually exists on yours.

By the way, I'm not connected with this site except as a forum participant. I've seen the cheat sheets for the D3200, which will be similar to those for the D3100, and they will generally get you a good exposure in a variety of situations. There's more than one way to do many things, but Moose's approach will get there. If you look around the site you'll get a pretty good idea of the kind of images he favors, which tend to be straightforward - brightly exposed, not oversaturated, and not burdened with special effects.