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Using x-ray film

X-ray film is great! Well, if you shoot anything upwards of 4x5", you can't beat the price, at least. And it does yield usable results - although it's a lot more iffy to use than regular photographic film. X-ray film is not intended for pictorial photography, but can be used for that purpose. It basically works a bit like a very old-fashioned, thin-emulsion, orthochromatic and double-sided film. There's a few exceptions to this: apart from the green-sensitive, orthochromatic film, there's also blue-sensitive film. I find it essentially useless for regular photography due to its narrow spectral response. On the other hand, there's Ektascan BR/A, which is orthochromatic, but one-sided with an anti-halation layer on the backside. It's also a T-grain film, so actually a very modern and high-tech product. Sadly, it's nearly impossible to buy at a reasonable price in Europe, so I use the regular green-sensitive, double-sided film that costs around 0.75 per 8x10" sheet delivered to my doorstep.

I mentioned that this kind of film is a bit difficult to use, so from time to time, I do some testing to further improve my working methods. So far, I have learned that:

  • Not all red LED lights are safe to use with green-sensitive film. I covered a red LED bulb with Rubylith film, which works like a treat.
  • Being double-sided, processing in trays requires very frequently turning the film over during processing to prevent uneven development. This prevents the notorious 'hot edges' (excess density along the film edges).
  • I also found that continuous agitation is the only way I can get even development. Any development scheme where the film rests for more than about 5 seconds invariably yields uneven development, I have found.
  • Lacking a hard top-coating, x-ray film is very sensitive to scratching. I develop it in an oven tray of the right size that has a Teflon non-stick coating, which is perfectly smooth. Glass would work as well, but is heavier. I have had limited success using plastic trays with a sheet of glass on the bottom; it sort of works, but the film still tends to catch on the edges of the glass, resulting in scratches.
But one of the main issues is that manufacturers of x-ray film don't publish data on effective ISOs or development recommendations for photographic use - simply because that's not the product's intended purpose. Conventional wisdom says that x-ray film generally has an ISO sensitivity of around 80 (but dependent on the temperature of the light and the colors of the subjects due to the film's orthochromatic nature) and needs a little less development than regular film. This means we're left to our own devices to figure out the details on exposure and processing.

So far, I've gone about using x-ray film in a bit of a haphazard way: rate it somewhere around 50 or 100 and develop to inspection in whatever developer seemed handy. While this yields usable images quite often, I get nowhere near the success rate I'd like for making e.g. Van Dykes. Hence, I did a little testing today. This wasn't intended as a formal Zone System test. I only made some Van Dyke prints and scans from the negatives to see if my development times were in the ballpark I needed. I do not have access to a densitometer.

First, I set out to establish a development time that I can use for further refinement, if/when I feel like it. I cut up a sheet of green-sensitive film to 4x5's and exposed some sheets at identical settings, rating it at 50 based on experience so far. I chose a scene that featured a 10-stop brightness range. I then manually developed each sheet in a tray, each time using an excess (300ml for one 4x5) of freshly made developer. I opted for Pyrocat HD, as it's economical and has so far proven to be excellent for my purposes (mostly Van Dyke brown printing and scanning). This yielded the following:

The first sheet I developed was the one that says 7m30s. It also yields the best Van Dyke brown print, although the 8m45s sheet is pretty close. The 6m15s sheet is clearly underdeveloped for Van Dyke prints at least, although it scans fine and still has plenty of shadow detail. For scanning and silver printing, this would be just fine.

I then decided to bracket some shots to see how the film responded to under- and overexposure. I shot the same scene (but with more subdued light) at ISO 25 - 50 - 100 - 200. I wanted to get some detail in the black tolex of the speaker cabinet left to the chair, underneath the plants, so I imagined this area to be around zone I to II. I chose to develop the sheets in one go in my Jobo, opting for a 9 minute development time. This is the result:

With these parameters, I could get away with ISO 100 if the shadows don't matter much. There's a little shadow detail I could rescue in digital post processing. But ISO 50 seems like a good compromise. ISO 25 gives more shadow detail, obviously, but the highlights are only preserved because the total brightness range of the scene was quite limited. ISO 200 is underexposed to the point of being unusable.

My preliminary conclusion is that for a scene of fairly normal contrast, ISO 50 is a safe bet for this film and developer, but I'll have to keep placing important shadows at zones III-IV for Van Dyke brown prints, as in that process, shadow contrast is limited in my experience. I may try some contractions and expansions to get a feeling for how to deal with low- and high-contrast scenes.

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