The verdict first: flash works for black and white paper reversal, but only just. With one Bowens Esprit 1000DX firing through a double-diffused softbox at three feet, I got a clean exposure on Ilford Multigrade paper through the Stenopeika Minutero 2.0. That is the headline result.
The more interesting finding, and the one I am taking forward to the portrait box camera project, came by accident: summer daylight is dramatically more powerful than winter daylight on paper. A five-second exposure to direct sunlight leaking through a small gap in my curtains overexposed a sheet that, back in December, would have needed eight full seconds of front-on shooting to expose at all. That changes what I might need flash for at all.
Here is the experiment, what went right, what went wrong, and the broader thing it taught me.
The problem I was trying to solve
Black and white paper reversal uses photographic paper as the capture medium, which has an effective ISO of around 1 to 5 depending on the developer combination. That is much slower than any film stock you would normally shoot, which means exposures are long.
Back in December last year, shooting portraits on the ULF box camera with available light, I was working at around 7 to 8 seconds at f5.6 wide open. Almost nobody can hold properly still that long, especially for a face-on portrait where you want the eyes sharp. The result, even with cooperative subjects, was soft on the eyes and slightly blurred everywhere.
So flash. The hope was that a strong flash burst would lay down enough exposure that the ambient bit before and after became insignificant, and I could effectively freeze a subject in a fraction of a second of light.
The flash arsenal
Since getting back from Canada earlier this year I have been quietly assembling enough flash power to make this work. The full kit now is:
- 3x Bowens Esprit 1000DX studio strobes
- 1x Bowens Gemini 500
- 1x Hyundai 400Ws (the original one I had before)
Total available power: 3,900 watt-seconds.
For this first test I did not bring everything out at once. The reason: using all 3,900Ws in a single shot would mean three separate strobe heads, which would mean three separate modifiers, which would mean three points of light hitting the subject from three different angles. That is not how you light a portrait. So instead I started with one 1000DX as a key light, one 1000DX as a rim, and saved the rest for later experiments.
This is the test: can a single 1000Ws strobe with a softbox give me a usable paper-reversal exposure?
![PLACEHOLDER: the studio setup, showing the Caronte 4x5 on a tripod, the posing stand, and the two Bowens 1000DX heads]
The setup
Camera: Stenopeika Caronte 4x5 (the field 4x5 I have been using throughout the paper reversal project).
Lens: Ross of London Teleros, an old telephoto wide open at f5.6. Brass and glass, classic character lens.
Holder: Stenopeika Minutero 2.0. This is the developing-in-the-holder system I have covered before on the channel. The Minutero fits straight into the Caronte using the existing back springs, no need for the graphlock attachments. Pour developer through the spout, wash, bleach, wash, clarifier, wash, open and re-expose, develop again. Image emerges in the holder.
Paper: Ilford Multigrade, which has become my standard for this process.
Lights: One Bowens Esprit 1000DX as key, modified by a double-diffused Neewer softbox, positioned about three feet from the subject. One Bowens 1000DX as a rim/edge light with a grid initially.
Subject: me, because nobody else was at home to volunteer.
The focusing system
This is the part that always makes paper reversal portraits possible despite the depth of field being essentially nothing. Because the Caronte has no rangefinder and you are not looking through the lens at the moment of exposure, you have to fix the focus mechanically and put the subject’s face exactly where the focus is.
The method:
- Set up the camera on the tripod, framed for a head-and-shoulders portrait
- Place a posing stand at where the subject’s head will go
- Add a spacer to the front of the posing stand equal to the distance from the back of someone’s head to their eyes. I measured my own at about 19cm, so the spacer is 19cm.
- Add a piece of tape at the end of the spacer. This is the focus target.
- Focus on the tape, very carefully, using a loupe on the ground glass.
- Remove the spacer, leaving the posing stand in place at exactly the right distance.
- When you sit down to be photographed, press the back of your head against the posing stand. Your eyes will be at the focal plane.
It works. The first time I did this I forgot to remove the spacer before loading the sheet and exposing, which produced one beautifully sharp image of a piece of tape. Lesson learned.
The shoots
I worked through several sheets in sequence, adjusting between each.
Sheet 1. Lens cap off, sit down, key flash fires, lens cap back on, dark slide back in. Develop. Framing was off but the exposure was workable. Progress.
Sheet 2. Adjusted framing, cranked the rim light up by a stop and a half, feathered the key light slightly off-axis. The rim light was now too direct.
Sheet 3. Removed the grids from both lights. Grids eat about a stop of light but they tighten the beam, and I needed to know whether the loss of tight control was acceptable. Turned both lights down a stop to compensate.
This is the one where I noticed the artifact.
There was a ghosting effect in the print, plus some unexpected exposure on one side of my face. At first I thought it was a chemistry problem. Then I realised what was actually happening: daylight was leaking through a small gap in the curtains behind me, and over the five or six seconds of total exposure (lens cap off, sit, flash, get up, lens cap on), that small gap of summer sunlight was contributing significant exposure to the sheet.
I closed the curtains properly and went again.
Sheet 4. Properly dark now. Clean exposure, no ghosting. The flash test was working. Two hours in, fifth sheet, things were starting to land.
Sheet 5 (the evening, with the kit reset). Switched to a tight face-shot framing, very close. Used the constant light flashlight to re-expose during the second-half development since I had no daylight to use. Print came back genuinely good. I am pleased with it.
![PLACEHOLDER: the final clean exposure portrait from the evening session]
The two big findings
Flash for paper reversal works, but barely
A single 1000Ws strobe through a double-diffused softbox at three feet from the subject is the minimum I could get away with for a head-and-shoulders portrait on Ilford Multigrade through the Minutero. That is not a lot of room to play with. If I want to position the light further away (which you would for a softer, more flattering portrait of a face), I lose stops fast.
Options to recover light:
- Remove one layer of diffusion from the softbox. Gets me a stop back, lets me push to roughly five feet.
- Use two 1000DX heads through the same modifier. This is the next experiment. Hard to do cleanly with most softboxes (they expect one head) but possible.
- Move to less diffusion entirely. Loses the softness which is half the point of flash for portraits.
There is also a practical worry: firing 1000DX heads at full power, repeatedly, is the kind of thing that eventually blows a flash tube. They are not cheap to replace. So the long-term setup needs to either run lights at less than full power (which means more lights total) or accept that I am going to be buying flash tubes.
Summer daylight is much stronger than winter daylight, on paper
This is the finding I was not looking for and it is the more useful one.
Five seconds of sunlight through a small gap in my curtains laid down enough exposure on the print to compete with a 1000Ws flash. In December, the same paper in the same developer needed 7 to 8 seconds of full front-on ambient exposure to register anything at all.
That is not a small difference. That is roughly a stop and a half of difference in effective sensitivity. The cause is well known to anyone who shoots UV-sensitive emulsions: there is much more UV in summer sunlight than in winter sunlight, both because the sun is higher in the sky (less atmospheric path) and because the days are longer.
Paper reversal is more UV-sensitive than most processes. The papers respond strongly to short-wavelength light. So the seasonal difference, which would be noticeable but manageable on conventional film, is dramatic on paper.
What this means practically: my 7-8 second exposures from December are not what I should expect for the portrait box camera in summer. They will be much shorter. Possibly short enough that I do not actually need flash at all for outdoor work, as long as I can find a reliable patch of summer sun.
I am going to have to redo my exposure calculations from scratch, using current sunlight.
What I am taking forward
Three things to test next:
- Outdoor portrait box camera shoots in summer daylight, with full re-metering. The hypothesis is that the 7-8 second exposures from December will collapse to something like 3 or 4 seconds, which is workable with a cooperative subject.
- Two-head flash through a single modifier, if I do still need flash for indoor or evening work.
- Constant light as an alternative to flash, since the flash approach has a ghosting risk on long ambient exposures (the flash freezes part of the action while the ambient continues to expose the moving subject). Constant lights would not have that problem.
It might end up being some combination of all three. The aim is to get the portrait box camera back out and start making real portraits with it, which has been the goal of this whole project since the paper-and-developer testing last year. Flash was one possible answer. Summer daylight might be a better one.
I will know after the next round of testing. More of this coming.