The decision to adopt 625 lines rather than 15,625 lines in television was based on practical factors related to the technical limitations and existing capabilities at the time.
Here are the key reasons behind choosing 625 lines:
1. Bandwidth Limitations: During the early development of television, the bandwidth available for broadcasting signals was limited. Using 625 lines enabled television signals to be transmitted within the allocated bandwidth while still achieving reasonable image quality.
2. Compatibility: The adoption of 625 lines was partly influenced by the desire for compatibility with existing radio and transmission systems. It became a compromise to provide an improvement over the 525-line system commonly used in the United States while remaining within the constraints of existing technology and infrastructure.
3. Standards Harmonization: In many countries, especially in Europe and parts of the world that adopted the 625-line standard, the choice was driven by a need for standardization. It allowed different countries and regions to use the same line count, enabling easier cross-border exchange and interoperability of television content and equipment.
4. Technical Feasibility: From an engineering perspective, implementing a 625-line system was technically achievable with the components and technology available at the time. Increasing the line count significantly beyond 625, such as to 15,625 lines, would have presented challenges in terms of signal processing, transmission, and storage capabilities during the era when 625 lines were adopted.
5. Picture Quality: While a higher line count can result in better resolution and image quality, the human visual system may not be able to perceive significant improvements beyond a certain point. At the time, 625 lines offered a suitable trade-off between image quality, bandwidth requirements, and practical implementation constraints.
Note: It's worth mentioning that the choice of line count varies based on the broadcast standards adopted in different regions. Countries like the United States, for instance, employ a 525-line standard (now outdated) and later adopted high-resolution systems with higher line counts, such as in ATSC standards (Advanced Television Systems Committee).
Over time, television systems have evolved, and today much higher resolution standards such as 1080p and 4K (which utilize a large number of lines) are commonly used. The transition to high-resolution formats occurred as broadcast technology and viewer preferences changed and technological advancements allowed for improved image quality and greater transmission capabilities.