Ilford SFX200 Infrared Sensitive Film
Some shots from a test roll of Ilford SFX200. This is a specialised black and white film with extended infrared sensitivity. The film is interesting in that it can be used to shoot fairly conventional images, while use of red and infrared filters can produce very exaggerated effects on sky and foliage.
The above image was shot in daylight with a dark-red filter. The sky and foliage (both foreground and on the distant mountains) have come out very dark compared to the people and stoney path that they are sitting alongside. I was a bit surprised at the strength of the effect, which also was stronger in this image than others taken around the same time and location.
With an orange filter, the effect is still strong, but generally the results are more in line with conventional film:
The spectral sensitivity of the film extends to 740nm, vs around 650nm for conventional emulsions. This makes it just about possible to use an R72 (720nm) filter for infrared photographs.
Surprisingly, the M7’s metering seemed to be fairly accurate with the filter attached and although I bracketed exposures, this was probably not necessary. The filter factor is pretty extreme – more than 6 stops – depending on the subject and lighting and likely mandating a tripod (as used below). Without the advantage of live-view LCD display, focus had to be set conventionally using the rangefinder, before being “tweaked” using the IR mark on the lens barrel.
The first two shots show the same scene both with and without the filter. It was again a very humid and hazy day. The IR filter appears to have helped cut through the haze and also brightened the distant foliage, giving the impression of more texture and detail on the distant mountains:
It is also interesting is how the apparent focal length of the lens (a Zeiss ZM 50/1,5 C-Sonnar) changes between the IR and non-IR shots. With the IR shot, the lens needs to be focussed closer than the normal calibrated infinity – and it seemingly has a shorter focal length as a result. I do not think that I have ever seen quite so much focus breathing in a lens before…
The stormy and windy weather was not the best for long-exposure plant photography, but the following show the classic IR foliage brightening (even if the subject is not great):
Subjectively, the image quality is very similar to HP5, but the tonality can be challenging when using a strong filter (for example, the grey mountains and sky in the first image). The lack of in-camera image preview means that it will probably take a few more rolls to better understand just how film, filter and subjects work together, but it is clearly an interesting film for black-and-white landscape photography – particularly if shooting in medium format.
Lastly, despite the odd focus-breathing, the Zeiss Sonnar seems to work very well with IR, with no obvious hot-spot. Perhaps one of the advantages of a very simple and un-exotic lens design.