I recently bought an Orion-18 28mm F5.6 lens and coded it as Summaron. The lens has the same structure. [I like it for its compactness and low 'profile'.] I use it on my M240 but bought it for Monochrom.
However, I notice some small tinge of purple on the top of this image in the sky. Should I use an IR/UV filter on this lens like on the M8? The Orion accepts 40.5 mm filters.
This reminds me of the M8. I remember JaapV once said the M240 has some IR issues. And would [sometimes] need a light IR filter. I tried the M8 filters by Leica on the M240 but did not like the result. Probably way too strong.
The following filters in 40.5 mm are available:
370-670nm
400-700nm
Which of the above is do you think appropriate?