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Calculating the working distance a

The object distance calculates the distance between the object (test sample) and the first principal plane of the lens. This is usually somewhere inside the lens. Approximately, this means the "working distance".
The often desired, so-called "free working distance" from the test object to the front of the lens can only be calculated by specifying the position and distance of the two principal planes and the real lens length. Therefore, the "working distances" calculated here are only an approximate value.

Calculating the working distance using focal length, object and sensor size


a= f´* (y / y´ +1)

Note: Even when using the drop-down lists own values can be entered. Please use the first entry "user def."!


Sensor size :
Focal length:
Length/ size of inspected object in mm (field of view FOV):
Calculated working distance:


We respect your privacy: we do not store any input, results or recipients. Send yourself your calculation with your own email program (MailTo-Link).

Working distance: calculate with pixel size sensor, focal length and component size

Note: Even when using the drop-down lists own values can be entered. Please use the first entry "user def."!

Sensor pixel count in X direction:
Sensor pixel count in Y direction:
Pixel size in µm:
Focal length of lens:
Object length in mm:
Object width in mm:
Object diagonal in mm:
Calculated sensor dimensions:
Calculated sensor ratio:
Calculated working distance:


We respect your privacy: we do not store any input, results or recipients. Send yourself your calculation with your own email program (MailTo-Link).



Calculation of working distance from object size and aperture angle

Object size / field of view in mm:
Opening angle of lens:
Needed working distance:


We respect your privacy: we do not store any input, results or recipients. Send yourself your calculation with your own email program (MailTo-Link).

Attention: Calculated working distances below approx. 100 to 300 millimetres cannot be focused using normal C-mount lenses. In case of F-mount lenses and other lenses for larger image circle diameters, the minimum lens distances are often considerably larger. By means of additional spacers, however, the lens distance can be reduced ("see calculation of close-up rings"). The calculated working distances refer to the optic centre of the lens housing. Especially in case of very small working distances of several centimetres, the calculated values are no longer realistic. In case of smallest image details and large magnifications please use macro-lenses which are specially designed for these applications.

Further details on optical calculations can be found in chapter Optical basics.

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