It may depend on what caused it. If you saved your files in Raw (NEF) format, you might be able to recover them at least part way. If you saved in JPG the chances are fewer. But if they are severely overexposed, even Raw recovery can only go so far, because blown highlights cannot be recovered.
If you are dealing with overexposure, and saved in JPG format, one program that has relatively good features is the free program "Faststone Image Viewer." If you find a copy of this, you will find, in the "colors" submenu, a couple of features that can help with bad JPG exposure. One is a highlight recovery feature in the "adjust lighting" section, which is better than most. Another is "Adust levels," which allows you to change contrast and to move the "gray point."
If you're shooting in NEF, try the Nikon program "Capture NXD" which is free on their site, or, if you're a bit more ambitious, the freeware "Raw Therapee." These programs both have the ability to do a few things better than the other Nikon program, View NX2, which probably came with the camera. Among other things, they can do a full five stops of exposure compensation.
If you can get any decent detail out of a picture, and the colors are still washed out, try converting to black and white.
All this is limited, however, by how far off your images are, and by what the cause is.
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If you are dealing with overexposure, and saved in JPG format, one program that has relatively good features is the free program "Faststone Image Viewer." If you find a copy of this, you will find, in the "colors" submenu, a couple of features that can help with bad JPG exposure. One is a highlight recovery feature in the "adjust lighting" section, which is better than most. Another is "Adust levels," which allows you to change contrast and to move the "gray point."
If you're shooting in NEF, try the Nikon program "Capture NXD" which is free on their site, or, if you're a bit more ambitious, the freeware "Raw Therapee." These programs both have the ability to do a few things better than the other Nikon program, View NX2, which probably came with the camera. Among other things, they can do a full five stops of exposure compensation.
If you can get any decent detail out of a picture, and the colors are still washed out, try converting to black and white.
All this is limited, however, by how far off your images are, and by what the cause is.