It's been a bit since I've used my sq. I was shocked at the current prices of backs and everything else. If you really want that back off. It's just a mechanical switch that is released by putting something similar to the slide along the bottom edge while pressing the release button. The ps glass and coatings are nicer and also add 1/2 stops for aperture. You can adapt 35mm easily with adapters. I also made a body cap pinhole which is approximately 80mm to give you some more options. Batteries last a long time.
