Roger,
Any time one does something unorthodox it is prudent to proceed with a
great deal of caution. Will you be able to positively retrieve the
piece of film after putting it into the slot? Will placing the filter
bugger-up any mechanism built-into the lens? Does dust enter the lens
when you place filters in that slot? etc. etc.
I don't know that lens so can't advise first hand. Too expensive for me!
So I am not going to recommend that you do it but if your feeling and
decision are that everything is safe then best wishes!
One thickness of black color reversal film is a start but two layers
are better. Of course two are not as good as one in terms of affecting
the performance of the lens so it is a matter of compromise. You can sort
of judge the effect of how opaque the film is by trying to look at a
bright source through one layer and then two.
Then make sure to use a tripod or something to keep camera steady for a
long duration exposure even with lens fully open!
Andy
Roger Eichhorn wrote:
Andy,
My 17-40 F4.0 L lens has a square slot on the camera end for a thin
filter. Could I cut a piece from the unexposed end of a roll of slide
film and use that?
Roger
On 16 Feb 2008, at 1:00 PM, ADavidhazy wrote:
Trevor,
Reversal film processed to Dmax as an improvised IR transmitting, light
blocking filter, should only be used in front of the camera lens. It
will
somewhat degrade the images as the film base is not optical quality.
On the other hand, a stack of deep Red and Blue filters will not affect
image sharpness quite as much ... hardly at all in fact.
Placing a gelatin Wratten IR filter behind the mirror in a DSLR may be
asking for trouble. In a film camera a piece 24mm x 40mm or so could be
taped (with very thin tape) across the image gate and between the film
plane rails of the camera. The filter material is so thin that the rails
provide enough clearance so that the film does not touch the tape or the
filter.
Contrast in an infrared image may be low for a variety of reasons. Since
you are working digital an adjustment with levels might help. Beyond
that
curves I guess may help further.
Starting out with a knockout image, however, is the best way to go IMO.
g'day!
andy
Before I bought my D200, I researched the IR possibilities and my
search
resulted in the only real negative of the D200 (IMO): really strong ir
blocking filter. Your Rebel took 30 sec for an exposure, eh? I have an
IR filter that I could try with it. The last time I did, I got a really
flat image. Where did you place the filter? I remember reading your(?)
notes on using the e6 film for an IR filter, but i got the impression
the
filter was placed behind the lens. Just wondering how I could adhere it
beneath my mirror without completely screwing up my gear. It'every
green
here in indonesia (a dramatic juxtaposition moving from egypt) and
I'd like
to find an alternative to buying a second dslr to send to the IR doctor.
