I've decided to use small tape measures(the itty bitty 3 footers) to check bello ws extension when I'm using both my lenses. I'll mark each inch and measure ext ension from the lensboard to the groundglass, unless somebody advises me that th is won't work.

I've read up on all the math for the calculations, but I'm not too proud to ask for you folks who are used to doing this, to take a 'looksee' at my math to see if these calculations are right.

Here is what I came up with....

I've decided to use small tape measures(the itty bitty 3 footers) to check bello ws extension when I'm using both my lenses. I'll mark each inch and measure ext ension from the lensboard to the groundglass, unless somebody advises me that th is won't work.

I've read up on all the math for the calculations, but I'm not too proud to ask for you folks who are used to doing this, to take a 'looksee' at my math to see if these calculations are right

Here is what I came up with....

12" Wollensak Bellows Ext. 13" Filter Factor 1.17 F-stop increase .59 12" Bellows Ext 14" Filter Factor 1.35 F-stop increase .68 12" Bellows Ext 15" Filter Factor 1.55 F-stop increase .78 12" Bellows Ext 16" Filter Factor 1.80 F-stop increase .90 12" Bellows Ext 17" Filter Factor 2.00 F-stop increase 1.00 12" Bellows Ext 18" Filter Factor 2.25 F-stop increase 1.13 12" Bellows Ext 19" Filter Factor 2.50 F-stop increase 1.25 12" Bellows Ext 20" Filter Factor 2.80 F-stop increase 1.40 12" Bellows Ext 21" Filter Factor 3.00 F-stop increase 1.60 12" Bellows Ext 22" Filter Factor 3.36 F-stop increase 1.70 12" Bellows Ext 23" Filter Factor 3.68 F-stop increase 1.84 12" Bellows Ext 24" Filter Factor 4.00 F-stop increase 2.00 12" Bellows Ext 25" Filter Factor 4.34 F-stop increase 2.17 12" Bellows Ext 26" Filter Factor 4.70 F-stop increase 2.35 12" Bellows Ext 27" Filter Factor 5.06 F-stop increase 2.53 12" Bellows Ext 28" Filter Factor 5.44 F-stop increase 2.72





14" Docter Optics Bellows Ext. 15" Filter Factor 1.15 F-stop increase .5 8 14" Bellows Ext 16" Filter Factor 1.30 F-stop increase .65 14" Bellows Ext 17" Filter Factor 1.50 F-stop increase .75 14" Bellows Ext 18" Filter Factor 1.70 F-stop increase .85 14" Bellows Ext 19" Filter Factor 1.84 F-stop increase .90 14" Bellows Ext 20" Filter Factor 2.00 F-stop increase 1.00 14" Bellows Ext 21" Filter Factor 2.25 F-stop increase 1.13 14" Bellows Ext 22" Filter Factor 2.50 F-stop increase 1.25 14" Bellows Ext 23" Filter Factor 2.70 F-stop increase 1.35 14" Bellows Ext 24" Filter Factor 3.00 F-stop increase 1.50 14" Bellows Ext 25" Filter Factor 3.20 F-stop increase 1.60 14" Bellows Ext 26" Filter Factor 3.45 F-stop increase 1.73 14" Bellows Ext 27" Filter Factor 3.72 F-stop increase 1.86 14" Bellows Ext 28" Filter Factor 4.00 F-stop increase 2.00