Everybody knows that analog photography provides two-dimensional records (film negatives) of the three-dimensional scenes, unfortunately the imaging techniques based on the photosensitive layers often suffer from curvature of field, so the main task for many engineers was to find a solution how to produce images exactly in one plane.
1960 Rollei integrated the so-called "flat glass" insert - plane-parallel glass plate, this technique comes from aerial photography, so the film could literally flatten all over the glass surface. By using those inserts it was possible to hold the film surface constantly unchanged and minimize the film curvature.
Not all the Rolleiflex models received the flat glass provision, you can identify them by opening the film back of your camera and check out the right film rail (film gate) for a small pin on the side. Back in the days (60s -70s) as everything in photography was analog and the hybrid digital process wasn't even possible, dust and even small scratches were a significant problem but today it´s not an issue at all especially if you use a new flat glass!
Because the original optical glass (made by Rollei) is impossible to find now in new condition, I´ve developed my own improved version of it.
This glass is the new generation true made in Germany floated flat glass with relatively low alkali content in the glass composition, therefore it has nearly colorless clear appearance. It also has innovative AR coating on both sides, high transmission of visible and infrared light and what is more important low micro roughness and completely flat over the entire surface. It combines superior quality and excellent flatness with outstanding optical, chemical and mechanical features as well.
VERY IMPORTANT, YOU CAN USE THIS INSERT IN COMBINATION WITH THE SPECIAL "FLAT GLASS" BACK ONLY, IT WILL NOT WORKS WITH YOUR NORMAL STANDARD BACK!