Symptom

I have noticed that when scanning the exact same region in SD mode and HD mode that the HD mode scans capture fewer fields than the SD scans. Why is that?

Cause

The number of fields required to scan a region of interest is based on two things:

1. The physical size of the region to scan.
2. The amount of overlap necessary to stitch adjacent fields together.

The uScope Navigator application overlaps images by a specified number of pixels in each axis. The minimum required overlap amount is dictated by the stitcher algorithm and is the same number of pixels regardless of the resolution of the camera.

When overlap is set to 128 pixels (the default):

• In SD mode (960×540) about 13% of the width and 24% of the height of each field are overlapped with adjacent fields.
• in HD mode (1,920×1,080) about 7% of the width and 12% of the height of each field are overlapped.

So, scanning identical regions in HD mode requires 6% fewer fields (in width) and 12% fewer fields (in height) or about 82% of the fields in an SD scan. This is why HD scans require fewer fields than SD scans.