(c) Eric Pederson, 2001-2002
I have just started using infrared film (well, I shot a couple 4x5 sheets of HIE in 2000, but that film was discontinued and I lost interest). Macophot has just introduced a new emulsion in 35mm and 4x5 sheets, which makes it attractive to those of us who work in both of these formats. So, like everyone else, I'm testing this new film (Maco820c). The best source of on-line information I know about this film can be found at http://www.pauck.de/marco/photo/infrared/maco/maco.html. To this, I'll add my own testing contribution with 35mm format. I have also been working with 4x5 sheet film in BTZS tube development. Since this is a fairly uncommon combination, I won't post my dev times, etc. here, but you can email me if you are interested.
The results of these tests, of course, are meant to help you decide the starting point for your own tests, not to be definitive. I do not have any proper testing of the film where I control the amount of IR light reaching the negative to properly evaluate contrast values, etc. Everything is based on a few field uses using a visible light spotmeter (actually the one internal to an OM-4Ti camera), but since this is approximately representative of how I (and most) will take photos using the film, it seems like a decent start.
As stock Xtol has become my usual developer, I used this for my testing. Since Xtol typically squeezes about 1/3-1/2 stop more actual speed out of film than D-76 (or equivalent), this seems a good place to start with such low exposure indeces as are necessary with this film. At slower E.I., I do seem to have about 2/3 stops faster film speed (i.e. it doesn't look pushed) than what I've seen reported for this film with other developers, suggesting that Xtol is a good developer to use if you are hoping to keep shutter speeds under 1 second. However, this is far from reliable testing so far. If anyone knows how to make a zone system type testing of densities with IR light please let me know. I have occassional access to a densitometer and have used that for calibrating exposure and development visible light b&w film, but I don't know how to do this with IR.
Small tank dev (with 30 sec agitation and then 5 sec every 30 sec agitation), Near-fresh Xtol (undiluted), 12min @ 20.5C (69F). No presoak, acid stop, Rapid Fix w/ hardener, Hypoclear, 20 minute wash.
Contrast was possibly N+ 1, though this was not not tested. All speeds given in ASA standard (ASA 12 = DIN 12 for conversion, i.e. ASA 6 = DIN 9, ASA 25 = DIN 15, etc.). The camera (OM-1n with Zuiko 35mm lens) has shutter speeds within 1/3 stop at all of the speeds used in these test exposures.
On slightly sunny (moderate haze and a few discernable clouds), mid-April midday, 44.1° N latitude. Metering was by averaging multiple spot readings off of approximately 18% reflectivity visible light surfaces (typically wood boards on structures) using the spot meter of an OM-4T (without any filtration) with known accuracy and a 90mm lens focussed on infinity.
No filter: EI 100 seems perfect
Orange: ca. EI 32
Red (25): ca. EI 25
IR-72 (89B): ca. EI 10
Reciprocity failure seemed small (ca. 1/3 stop) at speeds of 1-2 seconds. I have not tested longer exposures yet. Anyone got data on this?
IR-72 on lens with unfiltered strobe (Olympus T-32 mounted on camera hotshoe) ca. EI 4 (more testing with various surfaces required)
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Scanning of full-frame 35mm negatives with a flatbed scanner (HP Scanjet 5370c) with transparency adaptor for 100 dpi output. Saved as jpegs at 70% compression roughly 550x850 pixels. This should prove adequate to estimate exposure effects.
For reference of the
visual colors, here is
the scene of the barn photographed a few weeks earlier in March
(Velvia film, unfiltered) at about the same time of day, with a bit less cloud
cover. Since I was uncertain of reciprocity failure, I kept the shutter speed at
1/2 second for most exposures.
For comparison, here is a print from a 4x5 FP4+ negative and no filtration.
Since modern flash heads produce both visible and IR light, it is also possible to create IR photography using filtration over the flash head rather than over the lens/film. This won't eliminate visible light from exposing the film, but under many indoor circumstances, the amount of available visible light is inadequate to fully expose IR films (although Kodak HIE comes close to being useable as a regular (unfiltered) b/w film with available indoor light). Depending on the proportion of available light to strobe light, one should expect differing amounts of "IR-effect". IR filtering material is quite common as covers for various devices which communicate with IR pulses, e.g. the remote control of a television set. Sheets are available commercially and you should check with the manufacturer for the specification of transmission.
Since the filter blocks almost all visible light it allows for relatively unobtrusive flash photography. Please note however: This technique is not for unethical photography of unsuspecting/unwilling subjects. The flash illumination may not be visible, but the filaments on the flash head will still glow visible red, so it won't really be a secret anyway. It is a potentially useful technique for supplementing available light without disturbing seeing subjects with the strobe lighting. It might also be useful in circumstances which otherwise call for the use of IR film with inadequate available light (although non-strobe lighting may also be a possibility for still-lifes, etc.. A further potential advantage is that the filtering material need not be of high optical quality since it appears between the subject and the light source rather than between the subject and the film. Given the high cost of good optical quality IR filters this can be a significant advantage. Of course, the lack of filter on the lens allows for an SLR camera to be conveniently used as well.
Gerard Maas kindly provided me with a piece of filtering material for testing. It originally came from Serial Port Engineering Inc. which provides the specifications for this material which it sells and custom cuts. The chart is not very precise, but there is 0% transmission at approximately 660nm, 10% at 750nm, 50% at 800nm, and 70% at 900nm. It apparently was manufactured by Atohass Plastics.
I tested this filter material on two different flash units: an Olympus T-32, and an "Achiever" aftermarket flash. The T32 has an advertised GN of 32 with a dispersion angle to cover a 24mm lens on a 35mm camera. The Achiever flash has a GN of approximately 20 with an unknown dispersion angle (probably the equivalent of a 28mm lens), though it has a built in zoom fresnel lens mechanism which was not used. Both flashes were used on full manual and at least 10 seconds were allowed following the illumination of the "ready" light before exposure. All exposures were at 1/60 shutter speed to allow for dim visible light in the testing room for convenience in set up. The flash was set up on a hot shoe on the camera which was about 1/2 way between a mid-grey carpet and a white ceiling (2m or 7 feet high). There were no close side walls. The main subject was a highly visible-light reflective white board with exposure information, an open book for resolution checking, a Kodak 18% grey card, a color and full-step grey tablet. Since it is difficult to estimate IR-reflectivity of various materials, it is unclear how well these exposure findings will translate for other materials. In addition I photographed myself wearing mid-valued clothing for comparison with the various other objects. Finally, I made some sunlight exposures with no filter at ASA100 to ensure that the development could be considered my normal development (they indeed came out well exposed).
Development or Maco 820c (a different batch) was as per the method for available light photography given above.
No filter, Olympus flash, EI 50 produced a grey card reading of .59 over B+F.
Filter over Olympus flash, EI1.5 (ASA) or DIN 3 produced a grey card reading of .16 over B+F. This is disappointingly thin as no shadow detail will be available on such a negative. Similarly, the Achiever flash at EI 2 (ASA) or DIN 5 produced a grey card at 0.10.
While it is tempting to accuse the grey card of poor IR reflectivity, the self portrait with Olympus flash is clearly over 1 2/3 - 2 1/3 stops underexposed at EI 6 (ASA) or DIN 9.
This suggests that this combination of flash, filter, and film yield a realistic EI of about 1-1.5 ASA or DIN 2-3, which is unpractical for normal flash photography.
Since IR light was very weak with both flashes, the provisional conclusion is that the filter reduction was too great for effective use with this IR film. The filter transmission at 820nm is probably well under 50%. This filter would probably work better with HIE as the longer wavelength sensitivity of this film peaks closer to the indicated 70% transmission level of the filter -- plus the film is generally about a stop faster than the 820c. I estimate that an EI of 6-12 (DIN 9-12) might be feasible with the Kodak film and this filter. This would still require a fairly powerful flash (or a flash with greater proportion of IR light) for reasonable working distances.
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Last updated: 03-Jul-02
