Calculation question bellows

[Mainecoonmaniac]

Ralph rocks!

distances are measuredwithout tilt from the nodal plane of the lens. the precise location of the nodal plane is rarely known, but you can just assume the center of the lens and, in my experience, that is a fair assumption.to be most accurate use a focusing target and measure off the ground glass

So this is the tool I mentioned. Simple, elegant and no tape measure required. Thanks Ralph for being so generous. Also, please buy his book it's work every penny. I have it on my bookshelf.

 

[RalphLambrecht]

manythanks for the kind words.(as of now over 10,000sold)

 

[Christopher Walrath]

except...for this problem, all these different ways to do it boil down to the same thing...
bellows factor = (bellows length / focal length)2

+1. I use this. It's simple. Extension length (iris to film plane) squared divided by focal length squared. Doesn't get more simple.

 

[Mainecoonmaniac]

I'm one if them

manythanks for the kind words.(as of now over 10,000sold)

Cool. Check out Ralph's book and library here. Lots of cool templates.

http://www.waybeyondmonochrome.com/WBM2/Library.html

 

[/dev/null]

Thanks for all the feedback!

Today I will do some test shots and choose one of the calculations that fits my needs most.

I picked up a MOD54 development reel for my Paterson tank the week, so anxious to test that little baby as well. Will post the results soon.

 

[/dev/null]

So, it all worked out. At 210 mm and bellows at 30cm gave me 1 stop.

I noticed I wasn't measuring the light correctly, so I 'won' an extra stop with that. I also found a nice chart to double check my calcs

Thanks for all the help!