Hartshorn et al’s AFM black and white image of groups of SP-D multimers has both height and nm axes marked.  Six dodecamers were measured from that published original micrograph: in one method they were cropped and measured enlarged using the diameter technique-with the perimeter of the circle touching at least three CRD of the four arms (or half of the multimers). This method is quick.  And secondly by measuring each arm individually with a vector line (in which each segment of that line was measured individually by the process of breaking apart the line at “nodes”, rotating each line segments to horizontal and converting the lines from inches to nm using the scale of original and cropped images which were equally manipulated.

These 2 methods produced different results. The diameter method produced a dodecamer value of 131nm+/-11nm.  This value is not too far from that posted for just the diameter measurements from these same images: n=23 x=130.3nm +/-7.8.  It is however quite a bit smaller than from the cover image of Arroyo et al where no micron measurement bar was present on that image and thus SP-D multimers were were measured only “relative” to the mean of other Arroyo images where a micron bar was given.
(n=14 (two arms each); 144.49nm +/- 7.02nm).

In my humble opinion, these image probably wont give much info in terms of collagen-like domain brightness peaks. The resolution is just pretty low but they should be just fine for overall dimensions.