Explanation: This function allows multiple exposures as some analogue film cameras did. It means that several pictures are laid over each other and combined into a single new one.
In the menu you can choose how many images shall be made and if the exposure will be automatically adjusted so that the „sum“ of all pictures is not overexposed.
When done you have to press the shutter release button until the number of shots you have chosen is reached; during the multiple exposure the LCD display will show two overlapping rectangles as an indicator.
At the end the D5100 will save only the combined picture – the single shots from which it has been built are not available!
Recommendation: A nice feature that enables creative, even abstract pictures. Also subjects in different phases of a movement can be caught.
On the other side the same result is possible on the computer and there you have better control over the results.
If you use multiple exposure, leave the automatic exposure compensation switched on.
And please note: If you leave the menu without explicitly choosing the line „Done“ and confirming with the OK button the multiple exposures will stay switched off.
If you like to experiment best give it a try and make up your own mind.