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→DX film edge barcode: Added link to the DX Number page for further clarification of the use of different groups of DX code numbers. |
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==DX film edge barcode==
[[Image:Dx-film-edge-barcode.jpg|thumb|DX film edge barcode]]
Below the sprockets under each frame of 135 film is the DX film edge barcode. The barcode is invisible until the film has been developed. It is optically imprinted as a latent image during manufacturing. The barcode is used by photo finishers to identify each frame for printing. It consists of two parallel linear barcodes, one for a synchronizing clock called the "clock track", and the other encoding film data such as type, manufacturer and frame number, called the "data track".<ref name=":0" /> The barcode nearest the film edge (away from the sprocket holes) contains the data track. The data track sequence repeats every half frame, beginning with 6 start bits, followed by 7 bits of DX Number Part 1, 1 unassigned bit, 4 bits of DX Number Part 2, a 9-bit frame/half-frame number, and finishes with 4 stop bits.<ref>{{Cite journal|last=Gschwind|first=Rudolf|last2=Zbinden|first2=Erwin|last3=Trumpy|first3=Giorgio|last4=Delaney|first4=John|date=2017|title=Color negatives at the demise of silver halides|url=https://doi.org/10.5167/uzh-142330|journal=ICOM-CC 18th Triennial Conference Preprints, Copenhagen, 4–8 September 2017|volume=|pages=188-191|via=[[University of Zurich]]}}</ref> The 9-bit frame/half-frame number is called the "DXN" number (different than the [[DX number|"DX Number Part 1" and "DX Number Part 2"]]), and is an extension on the original DX edge code, patented by Eastman Kodak in 1990.<ref name=":0">Eastman Kodak Co. {{cite patent|country=US|number=4965628|title=Photographic film with latent image multi-field bar code and eye-readable symbols|status=patent|pubdate=1990-10-23|gdate=1990-10-23|invent1=Olliver|invent2=Johnson|invent3=Patton|inventor1-first=Richard|inventor2-first=Cortlandt|inventor3-first=David}}</ref><ref>{{cite patent|country=EP|number=0838718B1|title=Method of printing frame numbers from DX-coded photographic film not having frame number codes|status=|pubdate=|gdate=|invent1=|inventor1-first=}}</ref>
Some image processing software utilized by [[Film scanner|film scanners]] allow selection of film manufacturer and type to provide automatic color correction. Interpreting the DX film edge barcode may provide this information, permitting accurate color correction to be applied.
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