The GF1.4X TC WR is a 1.4x teleconverter for G Mount. Attaching the teleconverter to GF 250mm F4 R LM OIS WR allows for telephoto shooting at a focal length of 350mm (approximately 277mm in 35mm format equivalent) while maintaining superior image quality.
The maximum aperture is reduced by one F stop. As both the lens and the teleconverter are high quality, there’s hardly any deterioration in MTF when the teleconverter is attached.