Infrared fotograf elde etmek için
özel olarak EIR (Infrared Ektacrome) filmler üzerinde oluşan görüntüyü, saptanan görüntü
ışık dalga boyunu filtreler yardımı ile değiştirerek farklı renklerde görüntüler elde edilebilmektedir.
Üretilen filtreler sadece görülemeyen ışığın dalga boyunu değiştirdiğinden diğer çalışmalarda
kullanılamaz veya görüntüyü bozacağı varsayılarak efekt amacıyla kullanılabilir.
Infrared filtreleri kullanırken, diğer filtreleri kullanırken kullandığımız ışık ölçme tekniklerini
kullanarak poz değerini belirlemek gerekir. Filtrelerin faktörlerine göre ışık geçirme oranlarını
hesaplayarak diyaframı ayarlamak gerekir. Gökyüzünün çok açık mavi renkte olduğunda +1
diyafram eklemek iyi sonuç verebilir.
Kodak Infrared Filters and Spectral Sensitivity
Filter Types
There are two basic types of filters used for infrared photography (Wratten
numbers sorted in order of increasing effect):
Hoya screw-in filters R72 and RM90
For a cross-reference to other naming schemes from Hoya, Schott, or B+W see the
section “Links” below.
Note that the equivalent Wratten numbers that Hoya states for their filters (see
the boxes on the right) are not correct! The R72 is more comparable to the #89B,
and the RM90 is stronger than the #87C (somewhere in-between the #87C and the
#87B).
The ‘true’ infrared films – Kodak High Speed Infrared and Konica Infrared 750 –
exhibit their characteristics even when being exposed through a simple light red
filter, such as #25. However, pseudo-IR films, such as Ilford SFX 200, are quite
disappointing with these filters. For them, at least a #89B has to be used to
produce a sufficient degree of the Wood effect. I'm very happy with Hoya's R72.
It works very well with all true as well as pseudo infrared films. See also my
page A Comparison of B/W Infrared Films for more details and examples.
Most ‘true’ infrared filters are quite expensive. Not only the ones made of
coated glass, but also the gelatins from Kodak. A cheaper alternative is the
polyester #87 made by Lee, available in 75×75 mm and 100×100 mm. Another
inexpensive alternative is the dark red gelatin filter from Brenner in 80×80 mm.
It's somewhere between a plain red and a true infrared filter as it's not opaque
but far too strong for standard b/w films such as T-MAX.
Look-Through vs. Opaque Filters
Kodak Gelatin Filter #88A
Using opaque filters together with SLR (Single Lens Reflex) cameras usually
requires that you have to compose your shot without the filter and then put the
filter on before the exposure. This is a procedure is very annoying especially
for screw-in filters and only slightly less for slip-in filters of the Cokin
type. It becomes nearly impractical when fixing sheet filters with adhesive tape
behind the rear element of a lens, as often required for e.g. fisheye lenses or
medium format lenses with huge screw-in mounts. In practice, you'll need support
of a tripod in all these cases – and steady as well as very patient subjects, of
course ;-)
Mounting the filter between the film rails (BTFR) circumvents this problem (see
the section “Attaching Filters” below).
The easiest solution however is to use a camera with a range- or view-finder
instead of a SLR. A favorite of mine is the 6×6 Yashica Mat-124G with Konica
Infrared 750 or MACO IR 820c film and Hoya R72 filter. Even though these films
have a very low effective sensitivity with this filter (about 6-9 ASA), using a
tripod is not absolutely mandatory in bright sunlight. The smooth shutter of the
TLR (Twin Lens Reflex) Yashica makes it possible to hand-held longer exposure
times than a SLR with its mirror slap.
Finally, choosing a look-though filter such as the #25 or the filter from
Brenner avoids all this hassle. However, the infrared effect will not be as
strong as with the opaque filters. But this is more an issue with the pseudo
infrared films. Kodak HIE/HSI works quite well with a simple #25 red filter.
Attaching Filters
Brenner Gelatin Filter
After you have chosen the appropriate filter type, you have to decide about how
to attach it.
There are three popular alternative ways to go:
Front Lens Mount
Attach the filter by screwing it in the front mount or inserting it in a holder
such as Cokin's or Lee's. The filter may be made of coated glass, or uncoated
gelatin, resin, and polyester.
Rear Lens Mount
In some cases, it's not possible to use the filters in front of the lens, e.g.
for fisheye lenses or medium format lenses with huge screw-in mounts (my Carl
Zeiss Jena lenses use 86 resp. 95 mm filters!). Some of these lenses have
special rear mounts, but with the exception of a plain red filter, there are
hardly any IR filters available in these mounts. The solution is to simply tape
a gelatin or polyester foil behind the rear element of the lens.
BTFR (Between The Film Rails)
Attach the filter with a little help of adhesive tape between the film rails
behind the shutter or, as a more difficult alternative, in front of the shutter
but still behind the mirror if you're using a SLR. In this case, the filter has
to be made of thin gel or polyester. The details depend on your specific camera
body. Pay attention that it doesn't touch the film or gets into the delicate
shutter mechanics!
BTFR works perfectly for action photography, especially when using opaque
filters. Here's a summary of pros and cons:
Advantages of BTFR:
bright viewfinder, even when using opaque filters for SLRs, so no need to take
off the filter for composing and focusing and to put it back on for the exposure
one filter for all lenses, even super-wide, fisheye, long tele, etc.
no need to change the filter when changing lenses
no risk to forget mounting the appropriate filter
Disadvantages of BTFR:
awkward installation and removal of the filter if you can't dedicate a body for
this purpose
filter is fixed for at least one film (assuming that you put the filter in the
body and don't have changeable magazines)
dust, fluff, scratches and similar flaws on the filter are in focus and cast
more or less sharp silhouettes on the film (depending on the distance between
film and filter and the lens' focal length as well as f-stop)
reflections between film and non-coated filter may reduce optical quality
