[[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 6six start bits, followed by 7seven bits of DX Number Part 1, one unassigned bit, four bits of DX Number Part 2, a seven-bit frame/half-frame number, one unassigned bit, one parity bit, and finishes with four 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 seven-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.
