They definitely aren't 1/4 SD (DVD) though... The original series was SD, shot in SD for the early seasons with 1/4 res CGI.
The HBO Max release was 1080p with some wife screen usage... The extra pixels came from somewhere.
Series were shot on film. The HD versions are a mix of rescanned film and upscaled vfx shots
Series were shot on film. The HD versions are a mix of rescanned film and upscaled vfx shots