In the first place why would there be a need to remove the drop shadow. Amongst a few reasons, it could be that the effect is not attractive in the image, or it may not have been done in a good manner. The result with the effect is not appealing and it needs to be replaced with a new effect.
If there are ways to do an effect there are also ways to undo it. Learning both the processes are important for an editor. To start with he will need a high-resolution photo that no longer requires the drop shadow. If it is a GIF file then turn it into a Jpeg or any other high-resolution type. The lasso tool is used to select the shadow area. A little area around it will also be selected. If there are more drop shadow then they have to be selected separately and the process has to be repeated. The new selection is put in a new layer. The new layer will have only the shadow part. The step is to go to adjustments and check the brightness and contrast. If there is still any more unevenness to the tone then use the color balance. It will iron out the differences. It’s not yet done. A soft edge brush will be now needed from the eraser toolbox. All the residual areas will now be blended with the background. To be a little more perfect in this balance go to hue and saturation to adjust it further.
Sometimes a drop shadow is too dark and it may pose a problem in removal. Such areas can be easily patched up. How does one do that? Copy a similar patch from any other place, which is not textured. The process can be repeated of need be to balance with the original. When you zoom in, there will be more clarity. If you have an object like a glass window, copy a part of it where the shadow does no fall and add it across to the patch left by the shadow. Ah, to that you need to use a new layer and then flip it across.
A drop shadow can also be removed from a graphic or text in a similar way. Open the copy of the file that has the text and the graphic. Photoshop CS5 has the features by which it can be removed. The first thing to be done is to make a new layer. Start with the text layer, which has a drop down menu. It has attributes like stroke, fill, transparency and other effects. Select the drop shadow layer. This layer can be dragged in the trash bin. This may seem easy. But removing the drop shadow from the graphic are will require some patience. Once the layer has been selected, select the effect of the layer (not the object whose shadow is there). Select this from the menu. As you see the drop shadow in the same way drag and put it in the bin. Now the shadow effect is gone.