The first sentence is grammatically correct; the second is not. The idea is: It is considered that + Repin painted this picture (active)/This picture was painted by Repin (passive) --> It is considered that this picture was painted by Repin. Using "it is considered that" requires a change of verb tense as the structure is "indirect". (See the rules for indirect/reported speech here: https://www.tesol-direct.com/tesol-resources/english-grammar-guide/reported-speech/ ).