Since upgrading to MacOS Sierra, the PDFs I scan with Image Capture are much larger. My typical settings are 8.5x11 size, 300 DPI, "Text". With Yosemite, an average page of text was around 100KB. Now, an average page is around 1MB - 10x larger file size with no noticeable difference in quality.
Examining the scanned PDFs in Acrobat Pro, I see that the new one is using 8-bit grayscale. Previously, in Yosemite, it used 1-bit. Now there seems to be no difference between the two Image Capture options:
Black & White.
Is there any way to get 1-bit PDF scanning back? As a workaround, I am now using PNG for now, which has smaller file sizes.