Minolta Rokkor
How do I know what lenses and lens caps I need for my camera?
I have a lovely Minolta SRT 101 *don’t tell me it’s old, I love it because of that* camera with a Mintola 58mm lens. The lens also has MC Rokkor-PF on it if that matters. I want to get more lenses for the camera itself, as I’m a lens junkie *I have 3 others*, but I don’t know how I’d search for them, to know what’s compatible. The others I had gotten under recommendation by photo store clerks. Also, I got this camera a while ago, and the cap for the lens was cracked to the point that it would snap off on it’s own and bounce off the lens. I got rid of it, fearing a scratch, but now I wish I had a lens cap for it. How do I find one that will fit this lens?
Thanks in advance for answering my questions! 
Look carefully all over your lens. You should find some small writing that has a symbol that looks like a circle with a line through it, and a number in millimeters after it. That will be your lens cap size, and your filter size for that lens. For lenses, make sure they have a Minolta mount.
Look at the lens in this link. If it’s the same lens, then it takes 55mm filters and lens cap.
http://www.pbase.com/cameras/minolta/58_14_mc_rokkor_pf
Minolta MC Rokkor PG 50mm f/1.4 SLR Lens Review