[Author’s Note: The preflash time should be 2.4 seconds, not 1.2 seconds. My previous results were based on the test strip that was done under the amber safelight, so there was a lot more exposure than I had originally thought. Preflashed thusly, the ISO does in fact appear to approach 3, especially under sunlight.]
The Harman Direct Positive Paper (DPP) is a photographic paper that produces a positive image instead of a negative one. This allows the user to arrive at a frame-able image without contact printing, and also ensures that there is only one unique print in the world (barring internegatives).
The version I am using is the 4×5 fiber-based paper, which I plan on using with my two 4×5 cameras – the Toyo 45E and the Buschman Model D. In fact, tonight being the first time I have used it, I have already made 4 prints, though the results have been marred by a technical error. More on that later.
As some of you may know, the DPP is a pretty slow paper, rated at around ISO 3. In addition, out-of-the-box it is quite unusable, on account of its extremely high contrast. As a result, there is a need to preflash the paper to bring the contrast under control, and this in turn results in maybe a third of a stop gain in the paper speed. Preflashing is tricky, because there is no easy way to account for all the variables involved in a preflashing operation. For one, the paper has different sensitivity to different wavelengths, so different light sources will be absorbed either better or worse. Furthermore, there is often no way to accurately talk about the amount of light on the surface of the paper, since different apertures, lamp power, elevation of enlarger head, etc. will all factor in. Here’s where I come in. I use a Beseler 23CII-XL enlarger, with the PH140 lamp. Measured using the Sekonic L-558 meter, the light intensity I used was -0.7 EV, or 0.143 foot-candle, or 1.539 lux, and exposure was performed for 1.2 second in my case. [Edit: ISO 3 turns out to be quite an overestimation. After some testing, it looks like ISO 1.5 is closer to the mark.]
You should note that the 4×5 paper comes in two varieties. An older production run of the resin-coated version was apparently slightly larger than the normal 4×5 film holder (because 4×5 film is actually a little smaller than the nominal dimensions) and would not fit without trimming. Newer production runs have all been standardized to 4×5 film sizes. The FB ones never had these issues. Also, the FB paper is very thick compared with 4×5 film (I haven’t tried the RC version), so loading it into a film holder is a bit of a nightmare. You should definitely be careful not to leave a fingerprint on the paper surface. It takes me no less than one minute to load each one. That’s compared with 10 seconds for a 4×5 film! This also brings me to another problem. [Edit: Turns out the better quality film holders are the ones that will give you trouble. I used some old wooden ones and they worked just fine.]
After exposure and development, I found that my prints were coming out almost completely white. I adjusted the exposure time by one stop, but it did not help significantly. Then I realized that the paper was probably severely fogged. I proceeded to load, expose and develop one sheet in the dark, and it came out pretty well. It turns out that my safelight isn’t that safe after all. The amber safelight I use in my darkroom is not compatible with the paper, which is very annoying since red safelights are expensive at this point. I managed to DIY a solution by taping two red gels in front of my safelight, removing the amber plastic filter. I also put an ND filter and a sheet of plain white paper (to act as diffusion material). When I looked at the light by eye, it looked to be about the same brightness as my amber safelight. But when I got into the darkroom, even after waiting for 5-10 minutes, my eyes never got accustomed sufficiently to see in the dark. So I removed the ND filter and now I can just about see the print as it is developing (still worse than the amber safelight, for sure). [Update: Turns out the developer gets exhausted pretty quickly with this paper. I typically use RC papers for enlargement, and can usually get 2 days’ use out of the developer. But today, I wasted 4 shots when I developed them in the exhausted developer – the contrast was way too low, as was the density.]
At the end of the day, the paper is pretty average. Looking at the final results, I have to say I am not very pleased. Maybe I just need more time to work with this stuff. But thus far, I haven’t seen anything to suggest that the paper performs much better than regular enlarged prints. Of course, that may change when I finally get a picture worth scanning, and look at the final result at high magnification. Until then, I’d say just stick with film and enlargement. Or contact print a 4×5 film and cut it down to size, if you are so inclined.