Use an ND filter with IR film

[colrehogan]

Will an ND filter still do the same thing with IR film as with regular film? Sorry if this is a stupid question, but I have some IR prints that I have made that make me wonder if I'd be better off trying to reduce the glare off of one object in the picture.

 

[Jon Butler]

Will an ND filter still do the same thing with IR film as with regular film? Sorry if this is a stupid question, but I have some IR prints that I have made that make me wonder if I'd be better off trying to reduce the glare off of one object in the picture.

ND filter's are no problem with IR film but I like using a Polarizing & 695 IR
filter combined.

JON

 

[jim kirk jr.]

Like Jon I've used a polarizer,usually with a #29 or #25 red so I could see what I was doing.I've gone back and repeated a shot and found that in a less contrasty weather condition(clouds or overcast)with an 89b IR filter the results usually come out better than full sunlight and one of the above combinations.

Jim

 

[colrehogan]

Thanks! This particular shot I had used an 88A and it looks like the one side is over exposed quite a bit compared to the other. The object in question is a metallic object with sunlight reflecting off of it. What ND filter might be best? I have the Lee ND set (.3, .6 & .9, IIRC). I am leaning toward the .6.

 

[Helen B]

Diane,

Have you thought about asking Lee? I'm wondering how their resin ND grads are made (eg dye vs colloidal carbon?) and also recalling that Schneider/B+W, for example, do not claim neutral absorption beyond 660 nm for some of their absorptive ND filters (if my memory serves). Reflective ND filters are a different matter, but not what you are talking about.

Absorptive ND filters typically use colloidal carbon and often have a dip in absorption for wavelengths longer than around 700 nm and a rise in absorption for wavelengths shorter than around 550 nm - ie the makers are only concerned with the visible spectrum. This doesn't mean that the filter won't work in the near IR (will certainly work in the range that film is sensitive to), just that the factor won't be as high as it is for visible light. Dye-based filters could behave rather differently and may pass a lot more infrared.

How's that for vagueness? Oh, and I don't own any Lee grads (I use Schneider ND grads) so I'm spouting off outside my experience.

The best way might be to just try it with the Lee grads... and if you know anyone with a 'nightshot' video camera or even a normal video camera or digital camera...

Best,
Helen

 

[Robert Hall]

However...


Some Polarizers and nd filters are IR transparent. Keep in mind, most are engineered for visible light.

 

[pwitkop]

My understanding was that the dyes used in ND filters are IR transparent. In my industrial photo class we used ND filters with color IR film to increase the ratio of IR to visible light, making foliage more magenta, and skies darker.

Peter

 

[colrehogan]

Thanks to all for your replies. With regards to the filters, you guys might be right. I will send Lee and email and see if I can get any more information.

 

[Helen B]

I suspect that the only ND filters that are neutral beyond the visible spectrum are the reflective ones, but I've never seen those available as grads from the usual photo and cine manufacturers. I assume that you could polish part of the reflective coat off if you really really wanted a grad that was neutral for visible and infrared - you can get rectangular reflective ND filters.

Best,
Helen