WordPress conditional

Hi,

I am trying to load a CSS file only for a specific post template, I called it:

single-photograpy.php

which is a custom post template only for pictures posts.
In the header.php, I can’t find a way to target it.
This will target any single post (also the normal posts):

if (is_single()) { ?>

<link href="<?php bloginfo('template_url'); ?>/css/someCSS.css" rel="stylesheet" type="text/css">

<?php } ?>

while this one simply doesn’t work:

if (is_single('single-photography.php')) { ?>

<link href="<?php bloginfo('template_url'); ?>/css/someCSS.css" rel="stylesheet" type="text/css">

<?php } ?>

Is there a way only to target the posts from the single-photography.php custom post template?

[Moderator Note: Please post code or markup snippets between backticks or use the code button.]

THANKS A LOT