When I take pictures on my Nikon 3100 they keep coming out dull. They often look better on the screen as to when I look on the the desktop. I’ve been playing with settings and not had much luck. I even use a soft box, not that you could tell! Please help.
The primary problem here is simply one of exposure. The camera's metering system is not really smart — it doesn't know the difference between a white blanket that's dimly lit and a gray blanket that's brightly lit. It just assumes that everything is somewhere in the middle.
Your scene contains a lot of white. This fools the camera's assumption about the world, and as a result it underexposes.
You can compensate for this when shooting by adding one or two stops of exposure compensation. (EV +1). Or, in post processing (especially if you have the RAW file), brightening the exposure with the equivalent slider will help, too. (Not as good as getting the exposure right first, but should be just fine even with a DSLR that's a few years old.)
I’ve been playing with settings and not had much luck.
Stop playing with the settings and understand them.
Stop relying on luck and control the outcome. :o)
Do not wait until your baby is asleep or in a cute position, just take the picture of the same blanket with some pillow on it and change the settings.
First of all, the other answers commented about exposure. That is the first place to look.
Add 1 EV to it, and see the results. Add 2 EVs and compare.
You can use Aperture priority or Shutter priority, but as always, try to use manual exposure so you can change one parameter at a time.
Change the "Flavours" or Picture modes. Landscape, Portrait, Neutral. You probably have it on Neutral, change to Portrait.
Do not use Auto white balance. Define your custom white balance depending on your light.
Play with the direction of the light, not too flat, but a bit more to one side. This will give the image more contrast.
See if your light has enough CRI. I do not know if you are using some fluorescent lights.
Explore the option of doing some post-processing. Normally dull images are good! It is easier to add saturation and contrast than to remove them from an oversaturated and a clipped image.
Your photo is dull because the light illuminating the scene is dull.
That is, there is not much contrast in the scene.
As mattdm has said, left to its own devices your camera will meter the scene assuming the exposure should be centered in the mid-tones.
When most of the scene is white, this will result in underexposure of a low contrast scene. That's always going to look pretty dull.
They often look better on the screen as to when I look on the the desktop.
That's because the LCD screen on the back of a camera lies like a politician!
This is very common. It doesn't look like you're using bad settings it just looks like there's no real light. It looks like very low, reflected light. I agree with others that you should look at what you're shooting before the camera.
Here's the photo with quick, basic, MANUAL, levels, saturation, and contrast and a little brightness. I'd bet the corrected photo is more colorful and whiter than real life.