How to Realize Film Registration by Dot Copy Scan

Since the goal of dot-swipe copy scanning is to create a digital file that exactly matches the original film, the problem of orientation and alignment of the original film is crucial. Slight distortion when film is placed can have a big effect on the scan results. In particular, the effect of the film composed of four-color color separation films is more significant, because poor registration may cause problems such as moiré and color shift.
The solution to this problem is to provide some software and hardware tools to make the film more difficult to solve and to correct the distortion. There are at least three methods of this type of scanner currently available on the market to solve the problem of film registration.
(1) Registration ruler Some dot copy scanners provide registration ruler to help determine the film placement position during scanning. Like other registration rulers, the film is manually positioned on the viewing table. According to the registration ruler on the scanner, the positioning of the hole is required. This process requires that the human eye aligns accurately and cannot have any error. If the alignment is mistaken, it will cause distortion between the film and the film position.
(2) Software alignment Although the registration ruler can help the film alignment, the use of software alignment can achieve better results because the software can perform more precise work than humans through the operation of the computer.
Although there are slight differences between different software registration techniques, they usually locate the same target in multiple films and perform the registration of each film according to the chosen target. In general, use the register line on the film as a quasi-target. However, there are times when there is no register line on the film. In this case, significant details should be found on the image as a reference. It should be noted that it is necessary to select a content that exists on several films, such as the edge of a high-contrast object. This operation is generally performed by the operator looking at the scanned preview. After this work is done, the automated process can be started and each film can be automatically aligned to ensure that the scanned digital files are completely registered between several color plates.
In the process of making the film registration, the software must be able to carry out two adjustments of the vertical and horizontal position movements and rotations.
(3) Some dot-copy scanners on mobile platforms, such as Blu- ray, use a technology that simplifies alignment. The dot-copy scanner can rotate the scanning platform within ±5° to compensate for skewed film placement. . Since this amount of rotation is limited, the film can only be adjusted to the closest position, and then the software compensates. This saves the time it takes for the computer to correct the position of the film. (Hao Qingxia) ("Printing Weekly")