What is the difference between CTP plate and PS plate?

Apr. 18, 2025

The main difference between CTP plates and PS plates is that CTP plates are imaged directly from digital files, offering excellent precision, dot reproduction, and efficiency, while PS plates rely on traditional film-based processes, which have lower precision and involve more manual steps.

There are significant differences between CTP (Computer to Plate) and PS (Pre-Sensitized) plates in offset printing, covering aspects such as technology, workflow, performance, and application.

CTP (Computer to Plate) and PS (Pre-Sensitized) represent two different plate-making methods in offset printing. CTP plates use laser systems to image directly from digital files without the use of film, while PS plates rely on a film-based ultraviolet exposure workflow. This fundamental difference leads to substantial variations in resolution, substrate requirements, workflow steps, chemical usage, cost, and environmental impact.

CTP (Computer-to-Plate) plates and PS (Pre-sensitized) plates are widely used in the printing industry, each with unique characteristics suited for specific applications. However, CTP plates have largely replaced traditional PS plates due to their superior performance.

Comparison Table of CTP Plate and PS Plate

Comparison Item	CTP Plate	PS Plate
Dot Reproduction Ability	Capable of reproducing a tone range from 1%–99%, accurately reproducing intricate details	Difficult to reproduce fine dots, affecting high-precision printing results
Ink Balance	Excellent ink balance with minimal fountain solution, producing vibrant and consistent colors	Requires more fountain solution, diluting ink brightness and affecting color consistency
Registration Accuracy and Waste Reduction	Direct transfer from digital design, high registration accuracy, minimal paper waste	Relies on traditional film, large registration errors, numerous test runs, more material waste
Cleanliness and Print Quality	Plate surface is almost free from dirt, printing is clean and sharp, requiring minimal manual correction	Plate surface has more surface flaws, requiring additional cleaning and adjustments, affecting printing efficiency and quality
Emulsification and Edge Sharpness	Excellent water-ink balance, minimal ink emulsification, sharp and clear edges	More prone to ink emulsification, edges are less sharp, with slight loss of details

CTP Plate and PS Plate Plate-Making Process

CTP Plate vs PS Plate Plate-Making Method

PS Plate: Uses traditional chemical processes, requiring film exposure, development, and fixing steps to complete the plate-making. The process involves multiple steps and relies heavily on manual operation.
CTP Plate: Based on digital technology, the computer directly controls the laser to image on the plate material, eliminating the film step and part of the chemical processing, enabling fully automated plate-making.

CTP Plate vs PS Plate Production Process Complexity

PS plates undergo complex procedures such as film making, exposure, and development, and are prone to issues like dirt spots and film scratches due to environmental dust or operational errors.
CTP plates are directly output by machines, reducing human intervention and intermediate steps, resulting in higher stability.

Item	CTP Plate (Computer To Plate)	PS Plate (Pre-Sensitized Plate)
Imaging Method	Direct laser imaging (thermal, UV, photopolymer)	Ultraviolet exposure through intermediate film
Laser Type	Typically infrared laser (800–850nm)	Not suitable for direct laser, requires film
Plate Structure	Photosensitive layer (can be thermal, photopolymer, etc.)	Aluminum base: anodized layer + hydrophilic layer + photosensitive layer
Intermediate Steps	No film required, directly output from digital file	Requires intermediate film for exposure
Photosensitive Type	Thermal (thermal ablation, thermal crosslinking, silver halide)	Ultraviolet photosensitive materials
Development Process	Generally uses chemical or chemical-free processing (depending on plate type)	Requires chemical development after exposure to remove unexposed areas
Plate Type	Mainly negative type (exposed area retained)	Divided into positive type (exposed area dissolves) and negative type (exposed area retained)
Process Advantages	High precision, high degree of automation, saves time and materials	Mature process, lower cost, but complex workflow
Common Applications	Commercial printing, newspaper printing, fine printing	Traditional printing, low-cost publishing printing

CTP Plate and PS Plate Imaging Technologies

Direct Imaging vs Indirect Imaging

CTP systems expose plates directly from rasterized digital files, guiding laser engraving of the image without any intermediate film.
PS plates require physical film production (via imagesetters), which is then clamped onto a pre-sensitized plate and exposed to UV light in a vacuum frame.

CTP Plate vs PS Plate Exposure Methods

Most CTP workflows use infrared (IR) or UV lasers (e.g., 830 nm thermal or 400 nm UV lasers) to ablate or harden polymer layers, producing extremely sharp dots with minimal dot gain.
PS plates are exposed under broad-spectrum UV lamps through film, introducing scattered light and energy loss, which reduces edge sharpness.

Chemical Composition of CTP and PS Plates

CTP Plate vs PS Plate Photosensitive Layers

CTP plates typically use thermosensitive or pure photosensitive polymer coatings that directly react with laser energy, enabling "process-free" plates without wet chemical treatment.

PS plates have a multilayer structure, including anodized aluminum base, hydrophilic layer, photosensitive layer, and roughened surface, requiring chemical development after UV exposure.

PS plate developer has a pH of about 12, while CTP developer is usually 3–4 times more alkaline for rapid polymer removal.

CTP Plate vs PS Plate Aluminum Substrate Requirements

CTP substrates require stricter geometric tolerances: thickness around 0.280 mm (±0.005 mm), width tolerance ≤±0.5 mm, and surface roughness Ra of 0.45–0.60 μm.
PS plates use slightly thinner substrates (approx. 0.270 mm ±0.005 mm), with roughness of 0.60–0.80 μm; looser specifications are allowed due to the film-based imaging process.

CTP vs PS Plate Resolution and Print Quality

CTP Plate vs PS Plate Dot Reproduction

CTP plates can reproduce 1% to 99% tonal range and maintain excellent detail in highlights and shadows.
PS plates struggle with very fine dots, limiting high-resolution reproduction and subtle gradients.

CTP vs PS Plate Stability

PS plate quality varies significantly between batches, with poor long-term stability.
CTP plates undergo strict quality control, have high run lengths, and are suitable for long-run printing.

CTP Plate vs PS Plate Edge Sharpness and Registration

Laser imaging in CTP produces sharp edges, minimal dot gain, and high registration accuracy, reducing setup waste.
PS workflows involve film alignment and UV exposure, introducing registration errors and requiring more test runs and manual adjustments.

CTP Plate vs PS Plate Workflow Efficiency

Prepress Workflow

Typical CTP workflows skip film output and vacuum frame setup, going directly from RIP to plate, reducing turnaround time and manual steps.
PS workflows involve film output, inspection, vacuum framing, UV exposure, and development, increasing time and labor.

Chemical Processing

Many modern process-free CTP plates allow the dampening solution on the press to remove unexposed areas, eliminating the need for plate processors.
PS plates require separate developer, fixer, and often gum solution, in addition to wastewater treatment of spent chemicals.

CTP Plate vs PS Plate Operating Costs

CTP imagesetters and laser plate setters require higher upfront investment, but savings from eliminating film, reduced chemical use, and faster turnaround lower per-plate costs over time.
PS systems have lower capital cost, but ongoing expenses for film, chemicals, maintenance, and storage increase long-term operating costs.

CTP plates offer a fully digital, filmless workflow with superior resolution, registration accuracy, and efficiency, making them ideal for high-volume, high-quality offset printing. PS plates are still used where capital investment is limited or infrastructure supports film workflows, but they entail higher costs, lower precision, and greater chemical handling.

How to Choose Between CTP Plate and PS Plate

Choose CTP Plate: Suitable for companies pursuing high quality, high efficiency, environmentally friendly processes, and large order volumes.

Choose PS Plate: Suitable for companies with a limited budget, moderate quality requirements, or many traditional printing projects.

Criteria for Selection	CTP Plate	PS Plate
Print Quality Requirements	Suitable for high-precision, high-quality printing, such as catalogs, packaging, and advertising printing, capable of reproducing fine details and complex tones.	Suitable for general printing needs, such as books, newspapers, or low-cost printing, with relatively lower quality requirements.
Cost Budget	Higher initial investment (such as CTP plate-making machines and software), but long-term reduction in material waste and labor costs, suitable for large-volume, high-frequency printing.	Lower equipment and material costs, suitable for small to medium-sized enterprises or low-frequency printing projects.
Efficiency and Production Cycle	Digital plate-making process, fast plate-making speed, reduces manual intervention, suitable for orders that require quick turnaround, significantly improving production efficiency.	Requires traditional film-based plate-making procedures, which are more complex, resulting in a longer production cycle and affecting delivery speed.
Environmental and Material Waste	Excellent environmental performance, minimal paper waste, low fountain solution usage, meeting modern green printing demands.	More waste, especially during registration adjustment and testing, with high fountain solution usage, not environmentally friendly.
Technical Support and Operation Skills	Requires skilled personnel familiar with digital workflows and CTP plate-making equipment and maintenance, suitable for enterprises with modern technical support.	Lower technical requirements for operators, easily adopted by traditional printing plants, suitable for enterprises lacking modern equipment support.

Advantages of CTP Plate Compared to PS Plate

CTP plates offer superior dot reproduction, registration accuracy, and cleaner printing with better ink-water balance, while PS plates rely on traditional film-based methods with lower precision and more manual adjustments.