Re: Filter????

["Willem-Jan Markerink" <w.j.markerink@xxxxx>]

On  4 May 98 at 20:44, Jade7773 wrote:

> I recently bought some HIE and i havent been able to use it for lack of a
> Infrared filter, i dont even have a red #25 one for that matter.  But anyway i
> have a chance to buy a Hoya RM90 filter, for 20$ new.  So what filter is this?
> Is it good for HIE?  What other filters is it comperable to??  Most of all i
> am looking for the "dreamy-like" look, will this give me that????

According to Hoya brochures, the RM90 is equivalent to #87A, the 
darkest opaque IR filter in the Wratten system. B+W and Heliopan have 
a similar one, using Schott 1000 glass I believe.

The problem is that this color is most likely too dark for HIE, as
the cut-off line of HIE sensitivity crosses the cut-off line of the
filter transmission....the B+W brochure even mentions this.....so
even though you *could* get an image, you definately enter the
territory of *very* long exposures. Note that HIE & #87C (much
lighter than #87A) already results in an effective 10
ASA....wouldn't surprise me if #87A results in fractions of ASA. 
This is more a practical problem (tripod!) than that it makes it 
impossible to use this filter with HIE, but for a start in IR/HIE 
this is not the optimum filter.

Btw, what filter size is your Hoya filter?
If you decide not to buy it (or buy it, test it, and decide not to
keep it), I would be interested in buying it from you, for money or
a square #87C in Cokin-P size (or an equivalent of foil for between
the film rails).
In the future, I will probably arrange a custom order for similar 
square filters in #87B and #87A, and I like to have reference colors 
from other brands....sort of sick collecting virus if you like....;-))

If you want an overview of transmission data of red/IR-filters from 
Wratten, Schott, B+W, Heliopan, Cokin and Hoya, check my homepage, 
URL in the admin footer below.


- -- 
Bye,

Willem-Jan Markerink


      The desire to understand 
is sometimes far less intelligent than
     the inability to understand


<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]
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