I have a 380mm Telephoto lens that I would like to use on my Zone VI 4x5. Infinity focus is at about 8".

I am not sure how to figure the exposure correction for bellows extension with this lens.

My most frequently used lens for outdoor field work is a 150mm (6 inch) lens. With this lens, an extension beyond infinity of three inches ( nine inches total) requires one full stop of additional exposure . . .or 1/3 stop per inch. This works quite well outside with changing light and a cold wind blowing.


So how can I use this approach with the 380mm/15 inch telephoto? Seven and 1/2 inches beyond infinity would be one full stop Do I measure from infinity focus point at 8 inches of bellows draw?