[exim] logging $authenticated_id in prefered locale

Greetings,

My auth mech with openldap:
auth_login:                                                                                                             

    driver = 
plaintext                                                                                                  

    public_name = 
LOGIN                                                                                                 

    server_prompts = Username:: : 
Password::                                                                            

    server_condition = ${if ldapauth 
\                                                                                  

    {user=${quote_ldap:${lookup ldapdn 
\                                                                                

    {ldap:///ou=people,o=vlgroup?dn?sub?(uid=$1)}}} 
\                                                                  
    pass=$2 
ldap:///}{yes}fail}                                                                                         

    server_set_id = ${quote_ldap_dn:${lookup ldapdn 
\                                                                  

{ldap:///ou=people,o=vlgroup?dn?sub?(uid=$1)}}}                                                                     

    server_advertise_condition = ${if eq{$tls_cipher}{}{}{*}}

Where openldap dn in my prefered KOI8-R locale mode looks like:

dn: cn=Валентин Сергеевич Рябинин,ou=IT,ou=people,o=vlgroup
--skip--
uid=admin

And in openldap base64(UTF-8) normal view:

dn:: 
Y2490JLQsNC70LXQvdGC0LjQvSDQodC10YDQs9C10LXQstC40Ycg0KDRj9Cx0LjQvdC40L0sb                                          

 3U90JjQoixvdT1wZW9wbGUsbz12bGdyb3Vw                                                                                    

--skip--
uid=admin

When i authenticated on exim, my log message $authenticated_id looks like:

A=auth_login:cn%3D%D0%92%D0%B0%D0%BB%D0%B5%D0%BD%D1%82%D0%B8%D0%BD%20%D0%A1%D0%B5%D1%80%D0%B3%D0%B5%D0%B5%D0%B2%D0%B8%D1%87%20%D0%A0%D1%8F%D0%B1%D0%B8%D0%BD%D0%B8%D0%BD%5C%2Cou%3D%D0%98%D0%A2%5C%2Cou%3Dpeople%5C%2Co%3Dvlgroup

this is dumb format!

in  ../exim_4.66/src/recieve.c:
if (sender_host_authenticated != 
NULL)                                                                      

{                                                                                                          

  s = string_append(s, &size, &sptr, 2, US" A=", 
sender_host_authenticated);                                
  if (authenticated_id != 
NULL)                                                                              

    s = string_append(s, &size, &sptr, 2, US":", 
authenticated_id);                                         
  }
no answers..

So, i don't understand these string (it need for parse and for statistics).
How i can see logging message in normal mode? KOI8-R or base64(UTF-8).
Thanks.