Carl Zeiss Jena Flektogon 20mm f/4
The Carl Zeiss Jena Flektogon 20mm f/4 is a camera glass with a wide angle view and manual focus. It has a good resolution and a decent aperture with six blades which can produce pleasing bokeh. The lens has a sturdy build quality and weighs around 320 grams, making it a bit heavy to carry around. It has a filter diameter of 77mm, which is a common size for filters. The lens has an average brightness and uses lens elements with coatings to reduce flare and ghosting. The manufacturing time of this lens is not specified.
Average brightness in this league Has 6 aperture blades, this number of blades are commonly used. Having rounded blades provides out of focus circle shape closer to a circle.
77 mm lens filter diameter, commonly filter size, you have plenty of possibilities this lens deserves a good quality filter. 59 mm long, requires consideration if you want to carry in the camera bag. Weights 320 grams so plan ahead, carry only if really necessary.