Lens Information:
Magnification Calculator
• Focal Length Calculator
Glossary, Technical Notes

Focal Length Calculator

By knowing the image sensor format (sizes), you can calculate the focal length needed to view an object at a fixed distance.

By knowing the focal length of the lens to be used, you can calculate the dimensions of the viewed area.

The following tables show the related formulas

f = focal length (mm)
h = object vertical dimension
l = object horizontal dimension
D = object distance from lens

focal length calculation elements

Sensor Sizes:

sensor sizes

How to find the focal length
Choosing the suitable lens in order to view a subject with known dimensions at a fixed distance

Sensor format	1"	2/3"	1/2"	1/3"
If height of the viewed object is known	f= 9.6 D/h	f= 6.6 D/h	f= 4.8 D/h	f= 3.6 D/h
If width of the viewed object is known	f= 12.7 D/l	f= 8.8 D/l	f= 6.4 D/l	f= 4.8 D/l

How to find the object dimensions
Checking the dimensions of the viewed subject when using a chosen lens at a fixed distance

Sensor format	1"	2/3"	1/2"	1/3"
Calculate the height of the viewed object	h= 9.6 D/f	h= 6.6 D/f	h= 4.8 D/f	h= 3.6 D/f
Calculate the width of the viewed object	l= 12.7 D/f	l= 8.8 D/f	l= 6.4 D/f	l= 4.8 D/f

How to find the distance of a viewed subject
Calculating the right distance to view a subject with a choosen lens

Sensor format	1"	2/3"	1/2"	1/3"
If height of the viewed object is known	D=h f/9.6	D=h f/6.6	D=h f/4.8	D=h f/3.6
If width of the viewed object is known	D= l f/12.7	D= l f/8.8	D= l f/6.4	D= l f/4.8

After choosing your lens, take care that the working distance is not less that the minimum focusing distance. If this is the case, you must use extension rings or close-up lenses.