The Sefer Avnei Yashfei 4:36:3 was asked concerning a case where someone is in his house and sees the light from the lightning through his window, can he make a bracha or not?
He first brings the Rambam Berachos 10:14 which does not mention seeing the lighting rather just making a bracha on lighting.However,he writes that since that halacha is talking about many other things which dont require seeing it wasnt mentioned but who says one doesnt need to see lighting.
He then brings the Rivevos Ephraim 4:54:19(last Paragraph) (He mentions the shittah of the Tzitz Eliezer and the Shaarei Halacha in the tshuvah)who holds that seeing the light is enough ,his logic is that since we never see the actual lightning just the light it produces then any light is good enough to make the bracha.The Avnei Yashfei said that this is not a good proof according to his understanding.
He holds halacha lmaaseh that one should not make a bracha on non direct lightning,he also holds its a safek bracha lehakel. However,he writes that Rav Wosner and Rav Ben Tzion Abba Shaul hold that one does make such a bracha without the actual lightning bolt. The Tzitz Eliezer 12:21 also paskens this way. He then brings Rav Eliyashiv who held that one only makes the bracha on seeing the actual lightning,and this is how the Avnei Yashfei goes.