A slot is provided at the rear element to accommodate filters cut down from gelatin sheets.
Curved front element surface is highly exposed. A fluorine coating helps repel dust and grease, making it easier to clean.
The minimum focusing distance is just 16 centimetres so you can get in really close to further exaggerate spatial relationships.
The barrel tubes are sealed against the intrusion of dust and moisture. Weather protection measures also include a substantial gasket around the lens mount.