Hey Dusan,

Without seeing the file it's hard to say, but I'm the opposite polarity to you: I'm not surprised by this and would find the opposite result surprising. Unless your coating has flat transmission and flat phase (i.e., doesn't actually do anything) I'd expect the coating would affect the MTF. Anything that affects the amplitude and phase of the wavefront will affect MTF.

- Mark

Hi Mark

Good to hear from you. You are right about the coating and MTF but this occurs without coating, too and the basic question is why is the MTF different for 'all fields' mode as opposed to 'field 1' mode when there is one field only.

Kind regards, Dusan

Oh I see, sorry. I suggest you take the coating off (as it's not needed to demonstrate the issue) and post a ZAR of your file or send it to support@zemax.com. That's the easiest way to see what's happening.

My guess without seeing the file is that the sampling is changing in the two cases. I'd increase the sampling and see what happens to the difference. But as to whether that's a bug or normal operation, the support team will need to see a file that shows the issue. I had a look ata couple of files and ,needless to say, could not see any variance :-)

Support just confirmed there is a discrepancy between 'all fields' and 'Field 1' MTF values. However, not in real MTF but in diffractive MTF, which I forgot to mention. I apologize for that.

Polarisation has to be ON, which I mentioned.

Thanks, Dusan