Add this to the end of /etc/samba/smb.conf:
[camera-front]
comment= Camera: Front
path=/media/seagate_250gb/cameras/front
browseable = yes
writeable = yes
write list = camera-front
guest ok = yes
create mask = 0755
directory mask = 0700
public = no
[camera-front-readonly]
comment= Camera: Front readonly
path=/media/seagate_250gb/cameras/front
browseable = yes
writeable = no
guest ok = yes
public = yes
Ensure you're using user-level security:
security = user
Create the user camera-front:
useradd camera-front
and in samba's user database:
smbpasswd -a camera-front
... [enter password]