Instoscope
The Drem Instoscope is an extinction meter. When viewing through the ocular one could see a number of letters. The least visible letter is explained on the table which is wrapped around the instrument. The table shows the possible shutter-speed/aperture combinations for the least visible letter.
the extinction meter image by Mario Groleau (Image rights) |
Drem Instoscope image by Anssi Puisto (Image rights) |