Re: IR filters from Edmund Scientific

["R. C. Lacovara" <lacovara@xxxxxxxxxxx>]

Some stuff snipped ...

At 05:59 PM 1/2/01 +0000, Clive Warren wrote:

>I would be very interested in seeing the results from using these filters.
>
>Note that they are intended for industrial applications rather than 
>photographic applications.  Edmund states that the "Thermoset ADC filters 
>have the highest transmission and lowest haze".
>
>What does lowest haze really mean?  It may well be the case that the 
>filters are not appropriate for photographic use.

Well, no one, including Edmund's, is claiming that these are optical 
filters of the highest quality. However, they would make ok IR filters on 
light sources, at least if a little leakage in the green is ok. Some of 
them are faintly red, too, I seem to recall.

As for photographic use, I can offer the following. I have used the plastic 
filters in front of my IR image converter. I did not see any image 
distortion. However, my IR image converter is a relatively low-resolution 
device: it may mask imperfections which are visible on HIE.

Haze on an optical element generally tends to decrease the contrast of an 
image formed by an optical system which incorporates the hazy element. As 
long as the hazed element is not at a focus of the optical system, you 
shouldn't see explicit images of the questionable surface. As a note, by 
the way, I have heard that some zoom lenses or other long focal length 
lenses have a plane of focus near the front element: this would not be a 
good place to put a hazy filter. The plastic IR filter from Edmund's might 
make a serviceable IR filter.

It might be worth a try to put one of the Edmund's plastic filters in a 
Coken or other holder: I would be interested in the results. I'm not sure 
that this is any real savings over a Hoya R-72, however. I recently paid 
about $26 for one in 52mm.

Bob




>If anyone does do a reasonably controlled test of the filters I would be 
>delighted to include the results in the Infrared FAQ.
>--
>All the best,
>
>             Clive    http://www.cocam.co.uk
>                      Photographic Services, Filters and Equipment, 
> Infrared FAQ
>*
>****
>*******
>******************************************************
>*  To remove yourself from this list, send:          *
>*         UNSUBSCRIBE INFRARED                       *
>*       to                                           *
>*         MAJORDOMO@xxxxx                            *
>*----------------------------------------------------*
>*   For the IR-FAQ, IR-Gallery and heaps of links:   *
>*  http://www.a1.nl/phomepag/markerink/mainpage.htm  *
>******************************************************

*
****
*******
******************************************************
*  To remove yourself from this list, send:          *
*         UNSUBSCRIBE INFRARED                       *
*       to                                           *
*         MAJORDOMO@xxxxx                            *
*----------------------------------------------------*
*   For the IR-FAQ, IR-Gallery and heaps of links:   *
*  http://www.a1.nl/phomepag/markerink/mainpage.htm  *
******************************************************