I recently acquired a Ciro-flex TLR that I believe is a Model F (Raptar shutter, flash synch switch, 1/400 max shutter speed), but it has a plain ground glass focusing screen. I was under the impression that the Model F had a fresnel lens focusing screen, which is reported to be brighter. Three questions: 1) is this really a model F? 2) can I replace the ground glass with a fresnel lens? 3) if so, where can I obtain such fresnel lens ground glass? Thanks to all. I'm still waiting for a sunny day to finish the roll of B/W film that's been in the camera 15 or more years. <Chas> Everything in the frame must contribute to the picture.