The Prague Orloj — running since 1410, the oldest astronomical clock still working — caught in an albumen photograph by František Fridrich, the great documentarian of nineteenth-century Prague. The camera that would eventually replace the engraver here pays its respects to the machine that preceded them both. The Rijksmuseum's scan is sharp enough to read the dial's three simultaneous time systems: Old Czech hours, German hours, and the courses of the sun and moon. The town clock outlived every technology sent to record it.

Maker: František Fridrich
Date: c. 1865–1880
Medium of the original: Photograph
Original held by: Rijksmuseum, Amsterdam
Credit: Rijksmuseum, Amsterdam · via Wikimedia Commons
Rights: Public domain, verified
Catalogue number: PA-00539

As chosen: 18 x 24 in, art print, classic frame
Picture	18 x 24 in
Outside size	19.6 x 25.6 in
Depth	0.9 in (22 mm)
Weight	[[REAL PROOF NEEDED: shipped weight per size and frame]]
Hanging	[[REAL PROOF NEEDED: hanging hardware Prodigi fits to this frame]]
Material	Enhanced matte art paper, 200 gsm; acrylic glazing
Made in	Charlotte, North Carolina, by Prodigi

Before a size goes on sale, the file is measured against it: pixels per inch at that size, how much of the picture a crop would lose, tone and sharpness. A size that fails is not offered, so there is nothing to choose wrong.

How the print check works

Sizes offered
Size	dpi	Grade	How it fits
8 x 10 in	554	Excellent	Trimmed 2.9%
11 x 14 in	396	Excellent	Trimmed 4.7%
12 x 16 in	346	Excellent	Trimmed 9%
16 x 20 in	277	Excellent	Trimmed 2.9%
18 x 24 in	231	Excellent	Trimmed 9%
24 x 30 in	184	Good	Trimmed 2.9%

Sizes withheld
Size	Why
8 x 12 in	Wrong shape: a 19% crop
12 x 18 in	Wrong shape: a 19% crop
16 x 24 in	Wrong shape: a 19% crop
20 x 30 in	Wrong shape: a 19% crop
24 x 36 in	Wrong shape: a 19% crop
30 x 40 in	138 dpi; a historical scan is never enlarged
36 x 48 in	115 dpi; a historical scan is never enlarged
40 x 60 in	Wrong shape: a 19% crop