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IR filters + other filter?
Does it make any sense to use an IR filter together with e.g. an ND or a PLR, or do the latter affect only visible light?.

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Comments (5)

Why don't you just give it a try and see how it works out?Best way to find out....

Enjoy your infraredding (polarising)!!..

Comment #1

Ancient_Mariner wrote:.

Does it make any sense to use an IR filter together with e.g. an NDor a PLR, or do the latter affect only visible light?.

IIRC there's a specialized Fuji compact that you have to use an IR filter + ND to get exposures within the reach of the camera..

I'll assume you don't have an IR converted camera, one in which you pay someone to remove the hot mirror and replace it with an IR filter. In this case you're likely to end up with significantly long exposure times. Long enough that you'll carry a tripod. Stopping down the lens on top of that probably means you don't need a ND filter. I could envision some surreal effects with a stopped down lens and a ND filter for very long exposures..

Polarizers I'm not sure about. I read once where you could stack two polarizers and cross them such that almost no visible light reached the sensor. In this way you could get a false color IR image. This implies to me that polarizers block visible but not IR to the same degree..

Visithttp://irphotocom.proboards49.com/index.cgiThey have gear galleries and image galleries..

I'd like to see some posts of your IR experiments when you can post..

PS: HDR + IR seems to be hot on irphotocom in the last few months if you're thinking using a graduated ND to help the control the range of light. I tried it a few times, it has it's appeal. Of course much depends on your post processing technique and patience to play around with the image...

Comment #2

Mrxdimension wrote:.

I'll assume you don't have an IR converted camera, one in which youpay someone to remove the hot mirror and replace it with an IRfilter. In this case you're likely to end up with significantly longexposure times. Long enough that you'll carry a tripod..

Actually, no. I have a Nikon D40, whose sensor is very...IR friendly. I can even shoot hand-held @ higher ISO (400-800)!.

Stoppingdown the lens on top of that probably means you don't need a NDfilter. I could envision some surreal effects with a stopped downlens and a ND filter for very long exposures..

That's why I was wondering, coz I'd like to try very long exposures, but even with f/22, I can't get more than 4-6 secs. I guess I should get an ND (I don't have one) and give it a shot..

I'd like to see some posts of your IR experiments when you can post..

PS: HDR + IR seems to be hot on irphotocom in the last few months ifyou're thinking using a graduated ND to help the control the range oflight. I tried it a few times, it has it's appeal. Of course muchdepends on your post processing technique and patience to play aroundwith the image..

I'll keep you posted .

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Comment #3

OK, the results are out and they are very interesting indeed!.

This one is WITH a CPL, with the polarizing axis adjusted for maximum polarization (sun was aprox 70 deg left).

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The next one is without a CPL:.

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Both images were shot in RAW and were treated EXACTLY the same in PP.My observations:1) it is obvious that the CPL affects the sky, significantly darkening it.

2) CPL exposure was 1.3 sec, non-cpl 1.6 (ISO, f number same). I have the feeling that the non-cpl image is slightly more exposed, which leads me to believe that the CPL does NOT require longer exposures. Thus, the question is:.

Would an ND filter be useless? Are ND and CPL filters blocking only visible light?.

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Comment #4

Well the polarizer does have an effect in your shots..

See the B+W filter handbook.http://www.schneideroptics.com/info/handbook/pdf/B+WHandbook_Full.pdf.

Pdf page 60 for their ND filters. It looks like the lower ND filters block a lot of IR, but the higher density filters begin to pass some above 700nm. I haven't found a transmission chart for polarizers. I also don't know how well these transmission charts would apply to other brand filters. I suspect the details of the optical glass, coatings, and filter material come into play...

Comment #5

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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