Old school film to Laserdisc transfer: Why they are different from modern releases.

 
I use to be an old school I.A.  35mm Motion Picture projectionist. When handling film, you had to be real careful not to scratch the print, and that meant wearing protective gloves and making good proper splices , threading the damn projector correctly, thereby not making the loops to big or small to ensure that the print would not get scratched. It also meant screening the print, not to mention maintaining the equipment . Any mistake you made might cause damage, which would end up on screen (as dirt or scratches, bad splices, etc.) I became so familiar with the types of film stock and prints, I could tell you the type of film stock ( Fuji , Kodak - Estar /  Technicolor / Eastman , etc- that was being projected -simply by looking at the screen.     These 35mm positive prints were used in Telecine machines.
Go to this link:
Film stocks   
if you want to know more.

Telecine (/ˈtɛləsɪni/ or /ˌtɛləˈsɪniː/) is the process of transferring motion picture film into video and is performed in a color suite. Telecine enables a motion picture, captured originally on film stock, to be viewed with standard video equipment, such as television sets, video cassette recorders (VCR), and Laserdisc. This allows film producers, television producers and film distributors working in the film industry to release their products on video and allows producers to use video production equipment to complete Tv production, such as was done in Star Trek : TNG.

So, since every print was different, it meant that very release of a Laserdisc that was produced was also different. Since the days of Laserdisc, Telecines were replaced by High-Def film scanners , and now film has been replaced ( for the most part) with Direct to Digital Ultra High-Def video cams and then mastered in High-Def before being transfer ( down-converted) to Blu-ray, so gone are the days of having a film source.

The above was copied from Wiki. A 35 mm film print.  At far left and far right, outside the perforations, is the SDDS soundtrack as an image of a digital signal. Between the perforations is the Dolby Digital soundtrack (note the tiny Dolby "Double D" logo in the center of each area between the perforations). Just inside the perforations, on the left side of the image, is the analog optical soundtrack, with two channels encoded using Dolby SR noise reduction that can be dematrixed into four channels using Dolby Pro Logic. The optical timecode used to synchronize a DTS soundtrack, which sits between the optical soundtrack and the image, is not pictured. Finally, the image here is an anamorphic image used to create a 2.39:1 aspect ratio when projected through an anamorphic lens.

I love comparing the difference in film stocks and prints that you can clearly see in the film stocks ( and the film weave as it travels via sprockets through the gate ) and seeing the difference in the dirt and scratches that the different prints have while watching the Laserdisc, and then comparing the different Laserdisc releases of the same film-  before the days when everything was Digital - remastered in Ultra 8 and 4K. ( Not that I don't love that too.)