Just for some fun comparison, check out the following couple of images I found in the Library of Congress collection. These are mostly soldiers from the 95th Pennsylvania Infantry "Gosline's Zouaves" lounging around captured Confederate works at Manassas, VA in early 1862.
You'll see in the second image that the center foreground soldier's legging buckles are clearly visible and show five buckles/straps plus one underfoot strap. I am unsure of the exact height of the leggings but they appear to be close to the height of U.S. Sharpshooter leggings.
This next image is an unknown soldier from the 12th Maine or the 17th New York Infantry. The entire photograph shows a :12-pdr. howitzer gun captured by Butterfield's Brigade near Hanover Court House, May 27, 1862." The soldier you see here is apparently the only one in the squad wearing leggings.
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Brian WhiteWambaugh, White, & Companyhttp://www.wwandcompany.com----------------------------------
Randolph Mess, U.S. Sharpshooters