it's insufficient capacity. 2 AAA batteries are the limits. if you want a long-lasting solution, get a CR123 and it's holder. it has 3v already and lasts for a year or two at least.
have a look at this http://www.instantphoto.eu/diy/batt_conv2.htm or this http://www.instantphoto.eu/diy/batt_conv.htm (the rest of the site is not ready yet)