70mm Infrared Notes

by Steve Homer

The Basics

Kodak manufactures High-Speed Infrared film in several formats: 8x10 for the US government, the  now-discontinued 4x5 size for artistic photographers, 35mm for artistic photographers, and 70mm long rolls for aerial and scientific applications. It's all the same emulsion cut from the same wide stock. The Kodak catalog number for 150 foot rolls of perforated 70mm IR Aerographic film is 169 0841. In early 2001 the film was retailing for around $270 per long roll. From that roll you can bulk-load ten 15-foot cassettes of 65 6x7 frames each. This makes it only slightly more expensive per frame than 35mm HIE and 120-format black-and-white films.

Printed with low or normal contrast, this film yields grainless 8x10's and only subtle grain in 11x14 prints. I use it for portraits and figure photography.

These notes are a supplement to Jim Henderson's 70mm FAX (see below for the reference).

Camera Backs and Cassettes

70mm backs for perforated film are available for most interchangeable-back medium-format cameras, including the RB67 (but not the RZ67), Hasselblad, Graflex, and Bronica. You can also use the Hasselblad back on a Kiev 88. They all use a cassette of 15 feet of film. I think you get 80 frames of 6x6 from the 'Blad back.

Used backs are fairly easy to find at large dealers. Prices for used backs vary widely: the new backs are horribly expensive but the low demand for the used backs tends to encourage dealers to lower prices after they sit on the shelf for awhile. Bargain aggressively. Kodak recently discontinued all of its 70mm color negative films, so a lot of commercial portrait photographers should be selling their 70mm backs in 2001-2002.

Kodak also discontinued sales of the empty cassettes, so you'll need to find used cassettes. The cassettes are stored in a metal can, which is sealed shut with black tape. You must load the cassette into the back in total darkness. The felt seals on the cassettes are definitely not light-tight. As they age, they can get stiff and scratch the film; check your cassettes for damage and replace the cassettes (or the felt) as needed.

My factory-reconditioned RB back with brand-new felt seals was not perfectly light-tight in the infrared part of the spectrum. I'm told that the Bronica and Graflex backs, provided the felt seals are replaced every few years, don't leak. You'll probably want to test your back before shooting any critical projects. My film suffered from slight fogging after leaving the back exposed to ordinary room lighting for a few hours. If you use the camera outdoors, I recommend that you seal all four edges with electrician's black tape. Reinsert the dark slide whenever you're not taking pictures, or seal that opening with black tape too. (Also reinsert the dark slide when you change lenses.) I haven't found a need to tape the back shut when I use it in the studio. When I'm not shooting, I keep the back in a black bag from a box of paper.

In addition to the IR Aerographic, you can buy perforated Plus-X and Tri-X in long rolls. (Be careful to order the right type of perforation for your back: there are at least two different perforation spacings and also unperforated versions of these films.)

Pressure Plates

As with the 35mm HIE, patterns on the camera's pressure plate can be imprinted onto the negatives. This happens due to the lack of an anti-halation backing on the film: light can pass through the film, bounce off of the pressure plate, and be absorbed when it bounces back. Dimples and holes in the pressure plate can reflect more or (usually) less light than the main area of the plate. This is a problem for the RB, Bronica, Hasselblad, and Graflex backs (and probably any back with holes on the plate). With the RB67, for instance, you get a large circle to one side of the center and a row of small circles near one end of the plate. When photographing subjects like landscapes that show a great deal of irregular tonal variation, these marks are often undetectable; however, if the marks fall in an area of even tone (the middle of a solid-colored shirt or wall, for instance) they are likely to be visible.

To prevent these marks, you cover the pressure plate. I've used two different materials to cover the pressure plate of my RB: backing paper from 120 film taped into place, and black vinyl tape. The paper is not as thick as the tape, so the film transport was only slightly tighter than without any backing; however the paper abraded over time and needed to be replaced. The vinyl tape makes winding the film a bit difficult due to the resistance; however it seems to be very durable. You can also get black vinyl sheet material from "instant sign" shops that can cover the back without seams, but I haven't tried using this myself.

Bulk-Loading the Film

See Jim Henderson's instructions for loading the cassettes with film. Don't try to squeeze extra film onto the cassette; only 15 feet will fit on your developing reel. Like Jim, I think the 70mm bulk loaders are unnecessary.

Processing

Again, See Jim Henderson's instructions for more details. Like Jim I use a plastic Kindermann tank and steel Kindermann reel. Unlike Jim, I've had no trouble with uneven development when I pour the developer in through the lid; in fact this tank fills and empties faster than my tall four-reel 120 tank. You can buy 5 or 15-foot Jobo reels; the 5-foot reel can be hand-processed in the appropriate tank. I'm told you can even cut down and glue together two Patterson plastic reels to make a 70mm reel that fits a Patterson tank.

In theory, any developing process you use with 35mm HIE roll film should work fine with the 70mm version. Until recently I used TMAX RS developer mixed as Jim suggested, but with a significantly different time and temperature: 9 minutes at 24C. I invert the tank once per second for the first 30s, and then 10s/minute. Lately I've been using XTOL diluted 1:1 for 11 minutes at 24C. Once again, I'm using a significantly longer and hotter development cycle than I've seen anyone else recommend, so use it at your own risk.  I'm finding that the highlight detail with XTOL is significantly improved compared to the results I get with TMAX RS. I use Kodak Indicator Stop Bath for 30s, Ilford Universal Film Fixer for 4 minutes, and Orbit Bath hypo-clear for 30s. I mix all of the chemicals with distilled water. I use a 5-liter painter's bucket as a washer, with several holes cut in the bottom. I wash for 15 minutes (probably longer than necessary) and then rinse for 30s in Kodak Photo-flo. I hang it to dry without wiping (for fear of scratching the fragile emulsion).

Many people who use this film in 70mm or 4x5 format complain of pinholes. There was a notorious "bad" manufacturing run of this film a few years ago that was especially prone to pinholes. If you have trouble with pinholes (I never do), be sure to rap the tank hard against the counter to dislodge any bubbles at the beginning of the development cycle, and try using a water stop bath.

Print-File makes 70mm negative pages (style 70-3HB).

Printing

You can buy 70mm negative carriers for most 4x5 enlargers and some medium format enlargers. I haven't been able to find a 70mm carrier for my Besseler 6x7 enlarger, so I partially trim the sprocket holes off of the frames I want to print and use a regular 6x7 glassless carrier. The film is very prone to curling so you'll want to be careful not to trim in too far. (You'll need to make sure the "nubs" of the sprocket holes stay under the flanges of the pins in the carrier.) Presumably you could use a glass carrier with a 4x5 enlarger without trimming the negative.


Thanks to David Young and Bob on the IR Mailing List for helping me improve these notes.

For more information:

http://www.a1.nl/phomepag/markerink/mainpage.htm
70mm Infrared Notes by Steve Homer, 6/2001
Steve Homer Photography     Santa Cruz, CA  USA     shomer@cruzio.com