Interactive Depth of Field &
Diffraction limit Calculator

Limitations of Aperture Adjustment

The choice of aperture significantly impacts the performance of your lens. With this calculator, you can evaluate the optical limitations caused by aperture adjustments in seconds. This is highly practical for your daily workflow: You get immediate, reliable reference values and limits without having to extensively check or simulate these parameters in software tools like Zemax.

Depth of Focus: How much space is available?

While "Depth of Field" refers to the object space, "Depth of Focus" relates to the image space (the sensor plane). Take a look at the first graph (MTF vs. Defocus). The red edges in the diagram indicate exactly how much space on the object side is available to you. This marked area shows the range where the object can move away from the optimal focus while the MTF remain above the given value.

The Diffraction Limit

Even the most perfect lens is subject to the physical laws of light diffraction. The calculator automatically determines the diffraction limit of your specific setup. In the second graph, you can see the exact spatial frequency (lp/mm) at which the contrast drops to zero due to physical constraints (cutoff frequency).

The Interplay: Depth of Field & Diffraction Limit

Finding the perfect setting is always a compromise between depth of field and maximum resolution. Closing the aperture (higher F-number) increases your Depth of Field, but at the same time, the diffraction limit kicks in earlier, reducing your overall resolution. Our calculator helps you find the exact "sweet spot" between sufficient depth of field and the limitation set by diffraction for your specific application.

Technical information

The Depth of Field is calculated based on the equations for the diffraction limited and the effect of the defocus on the diffraction limit. There are approximations in the equations, it might not give exactly the same values as from optical simulation software.  A real lens will not be free of any aberration and will deviate from the diffraction limit, decreasing in the process the Depth of Focus of the lens compared to the maximum theoretical value calculated with this interface.