Is an IR/UV filter needed?

[Alberti]

Advertisement (gone after registration)

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?

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

[jaapv]

It could be slight IR contamination. I would use an IR filter in such a situation. There are no "light" ones, but it is true that you might need to tweak your colour tone slider slightly.

[Alberti]

Thanks. My idea is that the 370-670nm  is the less strong option; the band being wider, so interfering less.  But indeed, it is slight in this picture.

Just to show how it can be; For reference, using an Elmar 24: to me that is perfectly balanced. 

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

 

Edited September 20, 2020 by Alberti

[Good To Be Retired]

While I haven't encountered the exact issue you demonstrate, I have noticed that certain black fabrics exhibit a strong purple contamination.  I consistently use the Leica UV/IR filters and have not noticed any drawbacks.

[jaapv]

4 hours ago, Alberti said:

Thanks. My idea is that the 370-670nm  is the less strong option; the band being wider, so interfering less.  But indeed, it is slight in this picture.

Just to show how it can be; For reference, using an Elmar 24: to me that is perfectly balanced. 

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

 

Yes, there are different spectral transmissions but the intensity is not really relevant As long as the IR is cut off, the only difference might be in very deep reds.