Through Focus Geometric MTF Plot

  • 13 January 2023
  • 4 replies

Hello dear community,

How can I control the axial focus shift in the Through Focus Geometric MTF Plot ? Can any existing operands or any combination of existing operands be used for this purpose. 

Thanks !



Best answer by Andrey.Pravdivtsev 24 January 2023, 12:52

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Hi @Jacob.Jikku,

Please excuse me if I’m misunderstanding your question. To control the focus shift for the plot, if you go to the plot settings, you can adjust the Delta Focus parameter, as seen below. For more information on this feature, see the Help File: The Analyze Tab (sequential ui mode) > Image Quality Group > MTF > Geometric Through Focus MTF.



Hi Ethan, 

Thanks for your answer.

Sorry i could not explain my question correctly. I have here two configurations of one lens system. Lens data, Field data etc. are same for both these configurations except the Stop size. After ‘Optimization’ the difference in the ‘Through Focus Geometric MTF’ of these two configurations shows a large value like approx 0,2 mm. I would like to reduce this shift, especially at the on axis field. What i am looking for is some ‘Merit Function Operand/s’ or a strategy to control this shift. Which aberrations should i try to control to achieve minimum focus shift. 

Thanks again. 


Userlevel 2

Try to get the best MTF in the image plane. You can look on wavefront error for all waves and fields or control MTF directly at required frequency.

Hi @Andrey.Pravdivtsev ,

Thanks for the reply. I followed the steps you mentioned. In addition to it, to get the best MTF on the ‘on axis filed’, I also increased the weight of the Field 1 in the Sytem Explorer. It is effective in minimizing the on axis focus shift in the two configurations.  

I also tried operands like LONA but they were not so effective in my experience. 

Thanks for your input.