Hi Ahmad, You can see the current outline box (which probably contains a lot of empty space) with command: volume all showoutline true (it’s also in the Volume Viewer dialog, menu: Features… Data display options) To crop to a smaller box and save only that, you can draw the smaller box manually. To do that, choose Volume Viewer menu: Features... Subregion selection, and turn on the option to “Select subregions using” your mouse button of choice. More details on how to use the mouse to draw a box: <http://www.rbvi.ucsf.edu/chimera/docs/ContributedSoftware/volumeviewer/volum...> Once you have the box drawn how you like, click the Crop button in Volume Viewer (right under “Select subregions…) and then use Volume Viewer menu: "File… Save map as” to save that smaller-boxed map as a new file. Then when you close everything and then open the new map, it will be zoomed in more on the density. I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. UCSF Chimera(X) team Department of Pharmaceutical Chemistry University of California, San Francisco

On Apr 14, 2018, at 3:11 PM, Ahmad Abdelzaher <underoath006@gmail.com> wrote:

Someone shared a density map with me. I'm not sure how they "cropped" that particular density, but the file they sent me is huge in size, and contains only a small density that I have to zoom in and adjust every time I open the .mrc file.

How can I fix it?

Regards.