Hey Charlie,

You mentioned you saw this issue in 2025 R4 version.  In earlier versions, was there no issue?  Was this a regression from an older version of you think this RCWE was never matching the analysis?

I ask because I do not expect the Merit Function Operand to ever produce the same result as an analysis.  By default, the MF operand has some assumptions like ignoring vignetting/apertures when calculating operand values.  The thought process behind the MFE is “make it as fast as possible”.  So, when dealing with an MF operand, unless you take extra care to ensure the values are absolutely correct, I would always treat MF operands as being relatively correct.

If you need a final value for validation, always use the actual Analysis but if you need a quick relative measure of performance, especially between 2 different optimizations/systems, then you can use the MF operand.

For your specific situation, if you can share you file that is producing different results, the community might be able to help out more.

Hi Michael,

Thanks for the reply. In general I am indeed cautious about the evaluated values in the Merit Function, hence my double-checking with the plot/analysis tool in the example above. Anecdotally, I can say I’m usually able to get the results in agreement with the correct sampling in the MF operand. I was actually running 2024 until about a month ago when I updated to 2025 (R2, realized I put R4 above, which is a typo). I never noticed any discrepancies while using the 2024 version.

For me, the overlying issue is in the analysis/plot window - when you select Chief Ray reference, the title block (and text output) says Centroid reference, and vice-versa. I suspect the analysis shown matches the title block, as the RMS WFE values are higher when the title block says Chief Ray reference vs Centroid - which makes sense for a system with coma. Anyone should be able to open the RMS vs Field analysis window and confirm that the title block says “Chief Ray Reference” when “Centroid” is selected in the settings, and if you really want to confirm the analysis just load in a singlet and decenter it and compare the RMS vs Field with the different references.

In summary, I am fairly confident that the Centroid/Chief Ray Reference setting on the RMS vs Field Analysis is selecting/analyzing the opposite reference. Below is another example from the Rear Landscape Lens template (ZMXtmp8B5). Note again that I initially have Centroid selected as the reference in the settings, but the Graph and Text show Chief Ray, and when I switch the settings to Chief Ray reference, the plot/text show Centroid reference and the RMS values are much better (plots are on the same scale).

“Centroid Reference” selected in Settings:

“Chief Ray Reference” selected in Settings:

Finally, here are the evaluated MF operands for Centroid and Chief Ray reference, polychromatic on-axis. You can see the values match the text output from the analysis, but just reiterating that the analysis windows have the opposite reference selected in the settings.

Thanks,

Charlie