Isobel's Wratten #25 Filter

The twenty-five filter is mentioned by Isobel as part of her camera setup for photographing the Cybermen. She pairs it with her infrared film and telephoto lens, emphasizing its role in adapting her camera for low-light conditions. The filter’s inclusion in her proposal underscores her technical knowledge and preparedness, contrasting with the Brigadier’s sexist dismissal. While the filter itself is not physically present during the confrontation, its mention serves as evidence of Isobel’s expertise and the feasibility of her plan. The filter’s absence from the scene highlights the Brigadier’s refusal to consider her resources, reinforcing the institutional bias against her.

While Isobel’s 35mm camera is not directly involved in this specific event, its presence is implied as part of the broader context of gathering evidence. The camera represents the tools and methods being considered to document the Cybermen’s infiltration, contrasting with the Doctor and Turner’s technical examination. Its role here is symbolic, reinforcing the theme of proof and the urgency to act before the Cybermen’s plan is fully realized.