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PM490 / framebyframe

Components and Software of a Frame by Frame Scanner
GNU General Public License v3.0
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Measurements correct? #1

Closed simonbuehler closed 5 months ago

simonbuehler commented 1 year ago

hi,

i just came across http://8mm16mmfilms.com/8mm_Super8compare1Phil.jpg and the drawing of the normal 8 sprocket holes in your pdf isn't centered between the frames, are the measures correct?

PM490 commented 5 months ago

Thank you @simonbuehler, sorry for not seeing this request before. The SMPTE references, provide the distance between sprockets from top-edge to top-edge. That probably makes sense, since the claw mechanism would typically rely on that edge for positioning. In reviewing your question, I did see there was a distance that was incorrectly converted in the mm chart. The distance between center of the frame and edge of the film for standard 8 in mm was previously listed as 4.32mm when the correct conversion is 5.21mm. The chart was revised to make that correction.

PM490 commented 5 months ago

Revised chart

simonbuehler commented 5 months ago

Great, thanks for the update!

simonbuehler commented 5 months ago

i revisited my frame detection calculation and on my Standard 8mm images the frames are centered between the holes, while in the specs the frame would end on the top end of the next sprocket hole - do you have any idea if the specs or my footage is off?

grafik

simonbuehler commented 5 months ago

ok i think one issue is that the sprocket hole distances are not equal as the chart shows so other measures are also off film-gauges-all1-1500-51988bfb51d1b9c5d87534806c4788e4a3ef523f3484cc1e0b22befbc9780b76

PM490 commented 5 months ago

@simonbuehler thank you, and apologies for the confusion. For standard 8, there were a number of errors in the drawing. I have not been able to find the source (ANSI standard) for the sprocket dimensions and position, and in merging multiple sources, including the referenced SMPTE, I made some errors. To the best of the available information on hand, the new updated dimensions and overlap address your concerns. Please note that the image dimensions use corresponds to what SMPTE RP 19-1982 list as ¨Camera Aperture" which is the larger than "Projector Aperture". Hope this time nothing was missed, please let me know if you spot anything else, and thanks again for pointing the problems.

simonbuehler commented 5 months ago

perfect, looks good, thanks again!