Just to be sure about filter designations

[jim_royer]

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I have ordered two of the IR filters, which happened when I registered my new M8, as I'm sure many of you have done also. What can I expect on delivery time? From following the threads, seems like there will be a long delay.

 

Also, to clarify my thinking. Does the IR mean infra red and does the "cut" glass mean it's glass instead of a man made material.? The shortened words or abbreviations sometimes are not clear to me. Thanks. Jim

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[jaapv]

a. The shipping depends on the size of the filter. The 39 and 46 are shipping now.

b. All filters are made from glass (with some exceptions which don't apply here.)Glass imo counts as man-made too But I see what you mean. The filters we are talking about here are IR/UV cut, meaning they cut off Ultraviolet and Infrared.

The opposite is for instance IR pass or UV pass, which cuts out visible light.

[ho_co]

Jim--

Just to amplify a bit on what Jaap said, these are IR-cut filters because they literally block the transmission of infrared light by means of reflective layers that cause the IR frequencies to cancel themselves.

 

There are also IR-absorptive filters, in which the IR is absorbed by the material of the glass. A thin piece of IR-absorptive glass will reduce the transmission of IR by less than a thicker piece of the glass.

 

For a bit more info, see Edmund Optics - Mounted IR Filters.

 

On the opposite side are IR-transmitting filters, some of which are designed to block all visible light and therefore look opaque to our eyes.

 

In the terms that Leica has traditionally used:

the filters that block IR are 'IR-cut' filters;

the filters that absorb IR are 'IRa' filters;

the filters that transmit IR are 'IR' or 'IR pass' filters.

 

But since the terms are so similar, it's sometimes better tto explain, just as Jaap and I have done. Your question is a very good one.

 

--HC

[jim_royer]

Thanks very much, to both of you for your responses and information. That clears up the mystery for me. Jim

[sean_reid]

Jim--

Just to amplify a bit on what Jaap said, these are IR-cut filters because they literally block the transmission of infrared light by means of reflective layers that cause the IR frequencies to cancel themselves.

 

There are also IR-absorptive filters, in which the IR is absorbed by the material of the glass. A thin piece of IR-absorptive glass will reduce the transmission of IR by less than a thicker piece of the glass.

 

For a bit more info, see Edmund Optics - Mounted IR Filters.

 

On the opposite side are IR-transmitting filters, some of which are designed to block all visible light and therefore look opaque to our eyes.

 

In the terms that Leica has traditionally used:

the filters that block IR are 'IR-cut' filters;

the filters that absorb IR are 'IRa' filters;

the filters that transmit IR are 'IR' or 'IR pass' filters.

 

But since the terms are so similar, it's sometimes better tto explain, just as Jaap and I have done. Your question is a very good one.

 

--HC

 

What Howard just said... Thanks for saving me some typing Howard.

 

Cheers,

 

Sean

[ho_co]

Gee, Sean, you're welcome.

 

Usually, you find some obvious gap in my logic or description, so I thank you for the approval.

 

Don't worry, though. I've got enough opinions that I'm sure I'll mess up on the next one!

 

--HC