Epson Perfection V500 - Manual (Page 113)

If you are going to scan your image to a particular size, you should select the Target Size setting
after previewing it, but before adjusting your scan area (indicated by the marquee). This sets
the scan area to the correct proportions so your image will not be cropped unexpectedly.
For instructions on previewing your images, see Previewing and Adjusting the Scan Area . Then
follow these steps to select the Target Size setting.
Note for Home Mode users:
When you use the Thumbnail preview with film or slides, Epson Scan automatically
selects a target size of 4 × 6 in. for you. If you need to select a different target
size, complete all of the steps in this section. If you do not need to adjust any
target sizes, go to step 5.
You can choose a predefined scan size from the Target Size list. Click the arrow in the list
and select the size you want. A marquee (dotted line) proportioned for that size appears
on your preview image.