Bellow length for 240mm lens

I was wondering if somebody could give me an idea of how to calculate

the bellows length need for a fuji 240mm at a macro of about 1/2 to

1/4 life size? I am using an Ebony 45s with 270mm length, so i

don't know if i will need an extension?

<p>With a maximum extension of 270 mm and a 240 mm lens, you are not going to be able to do macro photography. The relevant equations are on the photo.net Lens Tutorial, located at <a href="http://www.photo.net/learn/optics/lensTutorial">http://www.photo.net/learn/optics/lensTutorial</a>. (With recent site reorganizations, one is unlikely to find this page unless one knows about it.) Using the equation M = (Si-f)/f, your highest magnification M will be M = 0.125, or an image of 1/8 lifesize.</p>

<p>The equation also shows that to reach M = 0.5 with a 240 mm lens that 360 mm of extension is needed, i.e., 90 mm additional extension on your Ebony 45s. I don't know whether this much extension would work well on your camera. To reach M = 0.25 (i.e., 1/4 life size), the required extension is 300 mm, or 30 mm addtional. This amount of extension is feasible.</p>

<p>If you want to use this camera to do macro photography, you could also use a shorter focal length lens. With a 180 mm lens you could get to M=0.5, i.e., an image of one half life size. Fuji, Rodenstock and Schneider make macro lenses with 180 mm focal lengths.</p>

<p>Some other threads describing related issues and how to use the equations in the photo.net Lens Tutorial: <i>LF lenses, bellows length & Closest Focusing distance</i> at <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=004kou">http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=004kou</a>, <i>Macro lens: Calculating subject distance with film distance</i> at <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=004yIU">http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=004yIU</a> and <i>Shortest and longest possible focal length</i> at <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=005GzQ">http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=005GzQ</a>.</p>

Michael,

Thanks for the info and the links. That was exactly what i was looking for and unable to find.