Re: Filters MBTFR

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

On 30 Apr 99 at 8:56, Stan Patz wrote:

> To the list,
> 
> There have been numerous references to mounting IR filters between the film 
> rails. It seems like a very good technique, especially with the more opaque 
> materials.
> 
> However, this filter material would have two surfaces to collect dust and 
> fingerprints. Since it is mylar or gelatin, it would be prone to scratches 
> from manufacturing or mounting, and it would not be flat, like a good 
> filter. Now, all of these flaws would be in close proximity to the film, so 
> they would be in focus and cast sharp silhouettes.
> 
> Isn't that a problem?

First: you are not limited to gelatine, since the following colors 
are available as thin polyester foil:

#25
#29
#89B
#87
#87C

The latter only in 0.4mm thickness, others 0.1mm (same thickness as 
gelatine btw). All US$0.50 pro square centimeter, mail me if you want 
more details.
It depends on the particular design of your film rails whether 0.4mm 
also fits....in my EOS-1 it does.

Second: a polyester #87C has been sitting in my EOS-1 for several
years now....still the first piece of filter, attached with the 
original tape....no problems with fingerprints, scratches or dust. 
And it sits flat as a mirror....this 0.4mm quality is quite 
sturdy....but the 0.1mm quality should be fine too....don't think 
it matters much where in the optical path you mount such a thin 
filter, even if it were not flat....large-format photographers do 
this behind-the-lens mounting all the time, and I haven't heard 
anyone even think about the filter being curved (to the point that 
they simply bend & tape the filter against the rear lens element.

(also available are #8 #12 #16 #21 for EIR applications....have
mounted #12 a few times for short periods of time (trips/holidays),
so I had a dedicated body for both HIE & EIR....an ergonomic dream
if you shoot in hectic/hostile conditions like I do while skiing,
otherwise you would still be fiddling with stupid filters for each
lens change, and some lenses are a pig to 'filter', like my Sigma
8mm/f4.0 (although for permanent non-opaque filters it is perfect, 
with separate internal filters (lens dismounts in two parts....8-)))

Simply try it, the proof is in the pudding!....:-))


--                 
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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