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UV/IR cut filter (silly) question...


M6J

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Today I dropped one of my UV/IR filters and it fell apart into 3 pieces: the black threaded ring, the glass and a flexible piece of metal that is used to keep the glass in place.

No big deal, since it wasn't broken I put it back together, but I was wandering if there is a "front" and a "back" side for the glass. It doesn't look like there is, but I just thought I should ask...

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If you hold the corner of a piece of paper so that it touches the glass of the filter, you should see that on the one side it can touch, but on the other side there seems always to be a little gap. Sampling one B+W and one Leica IR filter, the "touching" side faces the lens on both.

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If you hold the corner of a piece of paper so that it touches the glass of the filter, you should see that on the one side it can touch, but on the other side there seems always to be a little gap. Sampling one B+W and one Leica IR filter, the "touching" side faces the lens on both.

 

Wow! Carsten, how you knew that? :eek:

It is true, touching a white paper's side on one surface of the glass you can see that the reflection of the paper touches the paper itself, if you try the other side there is always a gap between the reflection and the paper itself.

So, the side of the glass that the reflection touches the paper is the "inside" one (the one that will face the front element of the lens).

There will always be something new to learn...

Thanks Carsten! :D

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The anti-reflective side has a more durable coating and should face out. The IR-reflective side should face the lens. Carsten explained how to know which is which.

 

The filter will work in either orientation but I interviewed one of the designers of the 486 filter who told me that the IR-reflective coating is not quite as scratch resistant as the AR coating.

 

Cheers,

 

Sean

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It will if using anything wider than about 50 mm, or so, on film. You'll have cyan drift in those Kodachrome slides and there's no way to correct it without complicated scanning, etc. I'd avoid it for sure.

 

Remember that cyan drift can be seen even with a 35 mm lens on the M8. That's an EFOV of about 47 mm. So even a 50 on film is pushing it.

 

Cheers,

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It will if using anything wider than about 50 mm, or so, on film. You'll have cyan drift in those Kodachrome slides and there's no way to correct it without complicated scanning, etc. I'd avoid it for sure.

 

Remember that cyan drift can be seen even with a 35 mm lens on the M8. That's an EFOV of about 47 mm. So even a 50 on film is pushing it.

 

Cheers,

 

Thanks,

 

Basically, I am using the 28/2 on the M8 and the 50 on the MP 3 with 400 iso color neg film.

 

I might just leave off the filter on the 50 and not swap the lenses out from film to dig.

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Thanks,

 

Basically, I am using the 28/2 on the M8 and the 50 on the MP 3 with 400 iso color neg film.

 

I might just leave off the filter on the 50 and not swap the lenses out from film to dig.

 

50 might just squeek by. When you have time, do some tests and see. I wouldn't go any wider (on film) with those filters.

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No, in the beginning we discussed this topic too, and checking our filters, we found that some B+W filters were assembled the other way. All Leica filters I have heard of are assembled the same way.

Yep, I just checked all of my filters and I found that one of my B+W filters has the "non-touching" side facing the lens. Why do they do this?

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Guest guy_mancuso

Barry you mean does the IR light hit first and the visible hit second. I would think the IR cut filter just bounces the IR light off and the visible light comes in, so if that is what they are saying than who hits the filter first should not matter. I would agree with that theory

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Yep, I just checked all of my filters and I found that one of my B+W filters has the "non-touching" side facing the lens. Why do they do this?

 

I have just checked all my filters (B+W) and they are all the wrong way around. Can this be changed or is it not worth bothering about?

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