ism ▁bin oc ular s ▁use ▁either ▁the ▁Ab be - K o enig ▁pr ism ▁( named ▁after ▁Ernst ▁Karl ▁Ab be ▁and ▁Albert ▁Ko enig ▁and ▁pat ented ▁by ▁Carl ▁Ze iss ▁in ▁ 1 9 0 5 ) ▁or ▁the ▁Schmidt - Pe chan ▁pr ism ▁( in vent ed ▁in ▁ 1 8 9 9 ) ▁designs ▁to ▁ere ct ▁the ▁image ▁and ▁fol d ▁the ▁optical ▁path . ▁They ▁have ▁objective ▁l enses ▁that ▁are ▁approximately ▁in ▁a ▁line ▁with ▁the ▁e y ep ie ces . ▁ ▁Ro of - pr isms ▁designs ▁create ▁an ▁instrument ▁that ▁is ▁nar ro wer ▁and ▁more ▁compact ▁than ▁Por ro ▁pr isms . ▁There ▁is ▁also ▁a ▁difference ▁in ▁image ▁bright ness . ▁Por ro - pr ism ▁bin oc ular s ▁will ▁inher ently ▁produce ▁a ▁br ighter ▁image ▁than ▁Schmidt - Pe chan ▁roof - pr ism ▁bin oc ular s ▁of ▁the ▁same ▁magn ification , ▁objective ▁size , ▁and ▁optical ▁quality , ▁because ▁this ▁roof - pr ism ▁design ▁emp lo ys ▁silver ed ▁surfaces ▁that ▁reduce ▁light ▁transmission ▁by ▁ 1 2 % ▁to ▁ 1 5 %. ▁Ro of - pr isms ▁designs ▁also ▁require ▁t ighter ▁toler ances ▁for ▁alignment ▁of ▁their ▁optical ▁elements ▁( col lim ation ). ▁This ▁adds ▁to ▁their ▁exp ense ▁since ▁the ▁design ▁requires ▁them ▁to ▁use ▁fixed ▁elements ▁that ▁need ▁to ▁be ▁set ▁at ▁a ▁high ▁degree ▁of ▁col lim ation ▁at ▁the ▁factory . ▁Por ro