or
Valuable formulae you will have to master..
when working with the Large Format Camera.
Close-up Photography

 
Click on square if you need the calculator ready..
General use Close-up Photography Miscellaneous
 
 
Close-up Lenses (General) 
These formulas will help you to find subject distance, depth of field, and field size when using close-up lenses 
The following quantities, except s, must all be expressed in meters. 
The answer will be then in meters!
Fs    = focal lengthh close-up lens = 1/D 
D     = Power on diopters (1+, 2+, 3+,) 
u      = Distance from CU-lens to subject 
s      = focusing-scale setting in feet 
Fc    = combined focal length of Cu-lens 
F      = focal length of lens 
W    = field width 
w    = negative width used.
Subject Distance:  
for infinity Setting:   u  = Fs =1/D for two lenses: 1/D1 + D2
For focusing Scale Set at s Feet :  u  = 1/ D+(3.28/s) *
To Find s and D for a given u:  1/u  -D =3.28/s 

Note: Take highest whole number od D (1,2,3,etc) 
that is not larger than 1/u. Solve for s
* 3.28/s is "power of focusing scale"  

This is equivalent to the power of a close-up lens which would cause the same change of focus. 

For example: 
changing the focusing scale setting from infinity to 3 feet is equivalent to adding slightly more than one diopter to the power of the close-up lens used.
Combined Focal length:  Fc  = F/ 1+FD
 
 
Calculate the magnification ratio by Michele Vacchiano  
Part One
R = magnification ratio; 
t  = bellows extention; 

f  = focal length.

 R = (t-f)/f How to calculate the magnification ratio , 
when you know the focal length of your lens and 
the bellows extention.?
Example:   Example: 
if  t = 200 mm and f = 90 mm: 
R = (200-90)/90 = 110/90 = 1.22
     
 
 
 
Calculate the magnification ratio by Michele Vacchiano  
Part Two
  Additional lenses can move the focal point from infinity to a distance which is the equivalent to the focal length of the additional lens. 

Normally, you know the dioptres of an additional lens. You can calculate its focal length like this:		  
Example:  f = 100/d (f = focal length in centimetres, d = dioptres) Example 
 if d = 3: 

f = 100/3 = 33.3
     
 
 
 
How to calculate bellows extension if you use an additional lens?  
Part Three
Step #1 d = 100/f Calculate the dioptric power of your lens Example: 
you have a 180 mm lens. 
Its dioptric power is d = 100/18 = 5.56
Step  #2   Add the dioptres of your lens to the dioptres of the additional lens. Example: 
you want add a 3 dioptres lens to your 180 mm lens, so 
3 + 5.56 = 8.56
Step #3   Now calculate the new focal lens of your system as follow: f = 100/d = 100/8.56 = 11.68 centimetres, or 116.8 mm
 
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