http://www.filmtools.com/tiffen-filters-81ef-nd.html3477Tiffen 4"x4" 81EF ND .3, ND .6, ND .9 http://cdn.filmtools.com/media/catalog/product/8/7/8770-etc.JPG185.35USDInStock/Camera & Accessories/Filters & Accessories/Camera & Accessories/Filters & Accessories/Camera Filters/More/Shop by Trade/Cinematographers/Filters & Accessories<ul>
<li><strong>4" x 4" 81EF Warming filter</strong></li>
<li><strong>O</strong>ne stop loss</li>
<li>Used to warm scenes</li>
<li>Partial color correction in tungsten based film outdoors</li>
<li>Slight blue cast</li>
</ul> The Tiffen 81EF Warming filter has about a one stop loss and is used to warm scenes, or for partial color correction when using tungsten based film outdoors and the desired look is to still have a slight blue cast.