The crop dialog allows you to display a specific area of your photograph. Move the crop area around with your mouse to get the exact spot you want to use.
by Width button
The photo will be resize to fit the width of the photo. If the photo ends up being shorter in height than the cell you are putting it in it will default to the minimum height setting.
The photo will be resize to fit the height of the photo. If the photo ends up being narrower in width than the cell you are putting it in it will default to the minimum width setting.
This displays the photo using the size it actually is with the crop area being set to the cell size. If the photo is narrower or shorter than the cell size it is expanded to fit in that direction.
Click in the center of the crop area to move it around. Click and drag one of the drag handles to resize the area. The aspect ratio will be preserved as you resize the area.