Compared to Mitutoyo M Plan APO NUV 100X:
At 365 nm spectral transmission of the 100X Mitutoyo and 50X PAL-50-NUV are both around 70%. Comparing a 50X and a 100X from 2 different manufacturers is a little bit daring, equipment and procedures might be quite different as well, but a Mitutoyo 50X NUV curve couldn’t be located.
And the PAL-50-NUV curve shows at 700 nm still more than 80% transmittance, Mitutoyo’s100X NUV curve starts to drop a lot at 630 nm and at 700 nm transmittance is barely above 40%.
With transmittance above 70% from 365 to 760 nm the PAL-50-NUV is a very universally usable objective covering the visual range as well.
And the curve for PAL-20-NUV looks even a lot better, staying from 350 to 810 nm above 70%.
There is no need to switch objectives for observation in the visible range, these 2 NUV objectives cover that as well.