so what ive read is that an 85mm lens is a good distance for portrait headyshot and head and shoulders type shots. my question is does this change from when working with full frame versus working on a crop sensor. ive read somewhere that if you not using a full frame camera you have to adjust for you camera. so in that case a 50mm would be roughly your 85mm equvelent. is this true. i just didnt think the full frame versus cropped would make a diffrence. maybe im wrong.