Bellow compensation.

[Mark Sawyer]

Just divide the bellows extension by the aperture diameter and you have your f/stop value...

[Tim Meisburger]

Thanks Mark, and Garrett. This is the simplest and easiest to remember explanation I've heard. I have, and have used, the Quick Disk, and it is easy and effective, but when I am wandering around I never have it with me (I could stick it in my bag, I guess).

[goamules]

Simple is, as simple does.

[WoodyBoinker]

Would the plots in this article be usefull for bellows compensation in the field?
Certainly would be an easy quick reference.

http://people.umass.edu/~rbhome/bellows15.pdf

[E. von Hoegh]

The chart in fig. 3 and a tapemeasure could be carried in the field, but it's better just to learn and remember the rule. It's really quite simple, and you're not as likely to leave your brain at home.

[Drew Bedo]

I think goamules has it right: Keep it simple. Find a simplified way to make the inverse square law work for you in the field and work with it till its automatic for you.

While I do not use this method, one way to simplify the correction would to pre figure the correction in thirds or quarters of a stop for your commonly used lenses and lay out a scale on the bed or rail of your camera. A different scale for each focal length of course.

This way you only calculate the correction once for each lens.

[Vaughn]

Just divide the bellows extension by the aperture diameter and you have your f/stop value...

But first you have to do the math (using the focal length and f/stop number of the lens) to get the aperture diameter, correct?

[Brian Ellis]

This is where English screws me up. Lets assume a 12 inch lens; 8X12 inches is 8 feet.
Does this mean the thing you focus on is 8 feet closer than infinity? or 8 feet father than infinity away?
Or it is farther than 8 feet away from the camera?
Or is the bellows 8 feet from its infinity position?

Sorry, I really shouldn't have talked about infinity. I meant no bellows extension if the subject on which I was focusing was farther than 8 x focal length of lens from the camera (didn't worry about farther from lens or farther from film plane or farther than somewhere else on the camera, since I was just eyeballing it anyhow I didn't think I needed to get that precise).

[cowanw]

Sorry, I really shouldn't have talked about infinity. I meant no bellows extension if the subject on which I was focusing was farther than 8 x focal length of lens from the camera (didn't worry about farther from lens or farther from film plane or farther than somewhere else on the camera, since I was just eyeballing it anyhow I didn't think I needed to get that precise).

I reckoned that and it is a good rule.
Regards

[Drew Bedo]

Vaughn: You are so right!