New old 50mm lens

Yesterday I got a nice little present. A Pentacon 50mm-F/1.8 lens, with an adapter to mount it on my Canon EOS-body.
This lens is produced between 1971 and 1990, so I cannot read the lens-information with the camera and store this into the photo, so Blipfoto cannot tell you this picture is shot at 50mm, F/1.8.

Today I learned a lot about the function of the aperture-size (F-value).
It started with yesterday's Blip of Stephanie, where she was experimenting with different F-values for her Blip. Coincidentally I just uploaded this little test of my own in which I tried to see the effect of the F-value on the DoF. (Shot with the 50mm-F/1.8)
Today I also did some testing on the effect of the aperture size on window-blinds.