Film Image Digitalizing

Introduction

Type of Sensor technology

There are two type of sensor technology; PhotoMultiplier Tubes (PMT) and Charge Coupled Devices (CCD) are used in scanners. They will be evaluated on their density range, signal-to-noise, resolution, and any extra benefits.

Scanner Type

Flatbed Scanner

• CCD sensor (Charge Coupled Device)

Drum Scanner

• PMT (PhotoMultiplier Tubes)

High End Scanning Technology

Drum scanners capture image information with PhotoMultiplier Tubes (PMT), rather than the Charge-Coupled Device (CCD) arrays found in flatbed scanners and inexpensive film scanners. Reflective and transparent originals are mounted on an acrylic cylinder, the scanner drum, which rotates at high speed while it passes the object being scanned in front of precision optics that deliver image information to the PMTs. Most modern color drum scanners use 3 matched PMTs, which read red, blue, and green light respectively. Light from the original artwork is split into separate red, blue, and green beams in the optical bench of the scanner.

Figure of PMT

• 1) FOCUS and APERTURE

• 2) PTM's One Tube for each RED, GREEN and BLUE Channel.

• 3) Dots per inch are taken by control of travel in direction and rotation of Scanner Drum.

• Each spot capture of light is split into its RGB Component.

• 1) Focus and Resolution is done at the Micron Level of a Material and sent to be split into its individual RGB Component.
• 2) Density of each channel is that of each individual Micron Sample split to its own RGB - PMT Sensor.
• 3) DPI is a physical process of Drum Control and Rotation.


What is PMT?

PMT stands for Photo Multiplier Tube, it is vacuum light sensor in which electronics are multiplied by secondary emission. Light (photons) falling on a Cathode release electrons. These are then conducted to Dynode layers, which convert light into an electrical current are measured at the Anode. The output signal is then sent out to the A/D Converter.

Strengths of PMT

• Resolution is at the grain of a material not dependent on a lens or scan area.
• Density of each channel is that of each individual Micron Sample split to its own RGB - PMT Sensor.
• DPI is a physical process of Drum Control and Rotation.

What type of scanner is being occupied inside Main Compuad Co., Ltd.?

Our company installed Linotype-Hell Tango Scanner from the year 1997 and directly purchased it from Heidelberg Hong Kong. Vertical Drum Scanner was the most advance design at that time. The Scanner - Tango is specially designed for high-resolution scans. With the Dynamic Density up to 4.2, even in dark areas the scanner can recognizes slight nuances and is able to create an optimal effect.

The supreme resolution is between 100 and 11000dpi. The meaning is the picture can be enlarged up to 3000%.

For example, full size of a 35mm slide film is 24mm x 36mm, if we scan it by using the maximum resolution setting 11000dpi, the output size will be 463.6MB at 8bit, 927.3MB at 16bit, if digital camera can capture the equal image, the sensor's (CCD, CMOS) capture ability should be 10394 x 15591 pixel. If we scan a big format slid film for example 4" x 5" by using 5000dpi, the output size will be 2.79GB at 8bit, 5.58B at 16bit, the sensor's (CCD, CMOS) capture ability should be 20000 x 25000 pixel.