Hello, I got what I hope was a good deal on a lens for my wife's K-70. My question has to do with the rear lens area. On all of the other SLR and DSLR lenses that I have used the rear lens opening is round. My new lens appears to have an adapter shaped like the Wide Screen TVs.
I have attached a picture of the rear of this lens. The engraved name of my lens is SMC Pentax FA 1:3.5-5.6 28-90 focusing Infinity - .4 M/1.3 ft.
Can somebody please tell me what that plate is for, and if I need to remove this for normal photo shooting purposes. I am sorry for how unexperienced we are, but everybody needs to start someplace and I would sooner look foolish with an elementary question than hurt her camera or have one of her first sessions ruined because I left something on that I should have removed.