How do I prevent Apache to log image in log file?

[mewth]

At first, sorry to my poor English.

Then, I want to prevent apache to log image in log file.
I already see the manual and web pages below:
http://forum.plesk.com/printthread.php?threadid=12836
http://forum.sw-soft.com/printthread.php?threadid=17630

And I do the following thigs.
1.Create a file named vhost.conf
in /home/httpd/vhosts/<my-domain>/conf/
and
in /home/httpd/vhosts/<my-domain>/subdomains/<my-subdomain>/conf/

2.Write this only in the each vhost.conf file;
SetEnvIf Request_URI \.gif image-request
SetEnvIf Request_URI \.jpg image-request
SetEnvIf Request_URI \.png image-request
CustomLog /home/httpd/vhosts/<my-domain>/statistics/logs/access_log combined env=!image-request

3.Run this;
/usr/local/psa/admin/sbin/websrvmng --reconfigure-vhost --vhost-name=<my-domain>
/usr/local/psa/admin/sbin/websrvmng --reconfigure-vhost --vhost-name=<my-subdomain>.<my-domain>

4.Restart apache

But apache is logging image in the log files.
Any ideas why it does'nt work?
I need your help.

mewth