Pin Registration for Scanning

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From Joe Owens, Mar 22 2007

Quote: Pin registration i(s) not being done on any real time LINE array CCD

Since pin registration requires the image to be stationary. A line array requires a totally constant physical translation (movement) to form an image. That's why pin reg works with whole- picture-at-a-time technology like the Arri, (full image chip) and of course, CRT flying-spot. Also, pin registration is usually defined to require double-perf (holes on both left and right sides of the medium)... so that leaves out Super16 in a way... its the one thing that always drove me crazy about the format... all that "S-" weave, both in terms of vertical geometry (non-linear stretching and compressing), but waving like a flag with the left side pretty stable, but the right side busy "in the breeze" fluttering away on the "unguided" side, sometimes much worse at the end of a roll.


Joe Owens Presto!Digital Colourgrade 302-9664 106 Avenue Edmonton, Alberta T5H0N4 +1 780 421-9980 jpo at prestodigital.ca


From Graham Collett Mar 22 2007

all film will naturally have an s weeve. Providing it is guided correctly it shouldn't cause a problem .. all perf registration is the optimum but its enough provide a well aligned transport to eliminate the weeve. The horizontal slicing specs of film these days are sufficient. Pin reg'd film is perfect for the first couple of runs maybe and then the perfs may not be perfect. Graham Collett


From Bob Michelletti Mar 22 2007

>Joe Owens > Since pin registration requires the image to be stationary. A > line array requires a totally constant physical translation > (movement) to form an image.

Actually a true pin registered scan can be achieved by moving the film over a linear array with a moving pin assembly or moving the linear array and holding the film stationary on pins. There is also pseudo pin registration where the image is stabilized based on an image of the perfs.

> picture-at-a-time technology like the Arri, (full image chip) and of > course, CRT flying-spot.

If I am not mistaken a CRT flying-spot does chase the film to a certain extent. That is how it maintains constant motion. This is most apparent in vari-speed.

> Also, pin registration is usually defined > to require double-perf (holes on both left and right sides of the > medium)... so that leaves out Super16 in a way... its the one thing > that always drove me crazy about the format... all that "S-" weave, > both in terms of vertical geometry (non-linear stretching and > compressing), but waving like a flag with the left side pretty > stable, but the right side busy "in the breeze" fluttering away on > the "unguided" side, sometimes much worse at the end of a roll. >

S-16 typically is registered with only 1 pin but should not move vertically and should not weave like an edge guided scan.

Bob Micheletti Engineer Universal Pictures


From Jeff Kreines Mar 22 2007

On Mar 22, 2007, at 12:56 PM, Micheletti, Bob ((NBC Universal)) wrote:

> S-16 typically is registered with only 1 pin but should not move > vertically and should not weave like an edge guided scan.

Note that a lot of weave in S16 is based on film shot with Arri SR cameras before they finally (after many years of keeping their head in the sand) switched to a spring-loaded edge guide from their previous fixed-width film channel. That channel, coupled with the loop required for the coaxial magazine, was a great contributor to weave.

Aaton cameras never suffered from this flaw.

Jeff "plus, their timecode is better" Kreines


From Peter Swinson, Mar 22, 2007

Bob Micheletti wrote

>true pin registered scan can be achieved by moving the >film over a linear array with a moving pin assembly or moving the >linear array and holding the film stationary on pins.

Good point, however the transport servo has to be VERY VERY accurate or, as Cintel's "failed" Klone scanner did, ignore servo stability but use a very accurate linear shaft encoder to trigger the CCD line sampling interval. It worked, but was slow! In that case the film was held in a pin registered clapper gate and the entire gate reciprocate up, down, and up for R,G,B scans

>If I am not mistaken a CRT flying-spot does chase the film to a >certain extent. That is how it maintains constant motion. This >is most apparent in vari-speed.

True but not in pin reg mode. In Pin Reg mode the transport stops and the pinned film is "Still scanned" by the raster.

Bear in mind that Pin Registration is only really useful for scanning film that was pin registered in the camera.

Many cameras do not use full fitting pins and rely on edge guidance. Pin scanning such film can provide worse weave than not pinning. In an ideal world there should be a scanner gate guidance system for every camera guidance system, to ensure that both camera and scanner guide the film at exactly the same points.

Further, film manufacturers only slit the stock with one accurate reference edge. Rumor has it that some cameras, mainly S16mm, use the other edge as guidance. If true then weave cannot be eliminated, unless a gate is designed for opposite edge guidance.

What we really wanted ands talked about many years a go were fiducle marks. A camera gate design that exposed marks on the stock just outside the picture area as each frame was exposed. Basically cross hair targets, a minimum of one above and one below the frame, but offset so the one below the frame can be differentiated from the other mark representing the top of the next frame.

These marks could then be scanned and used as steadiness targets and the whole picture could then be referenced to them as they were scanned or as a subsequent process. In the "good old days" if this system had been used these same marks could be "printed thru" to IP, IN or Release Print and any scan of any generation could have had perfect stability. However Fiducle Marks never took off!

Peter


--Rob Lingelbach 08:09, 23 March 2007 (PDT)