Pre-flashing Direct Positive paper from Ilford Harman
I am proposing to use Ilford Harman Direct Positive paper in my half plate camera.
Does anyone have experience of doing this? If so how, and for how long, do you pre-flash the paper to reduce the contrast, prior to the main exposure?
I have read the information sheet produced by Ilford Harman, but this is not making much sense to me! The notional speed of the paper is 3 ASA. Is there a formula to decide what % of the metered exposure should dictate the pre-flash exposure time?
i wish i could help you, but i haven't ever used efke or ilford's direct positive paper.
i poked around for you, and still came up empty ...
when i make conventional paper negatives i sometimes preflash my paper
to just before it is visible on the paper ... that is like .2 seconds stopped down a little bit ( maybe f8? )
i also use a developer that is partially used, and a water bath, and a developer that is "fresh"
and i go between the 3 baths for a good 2-3 minutes ... i am not sure how the direct positive paper
works if it is a vc paper, or something like " grade 3 " ... but these are tricks i learned just having fun.
i also expose in non-bright/contrast scenes/portraits ( read-- flat light ) so there isn't too much trouble.
the last paper negatives i processed i did so in caffenol c spiked with a little bit of print developer.
the caffenol was old+ used and i used IT in conjunction with the fresh developer and water and it turned out great !
you might try a few different methods with "test strips" so you don't use up all your
paper doing test exposures that didn't work the way you wanted ...
good luck ! i have wanted to try it, but my lack of funds has kept me away from it
seeing it might be addictive + more fun than my wallet wants me to have !
I have shot a lot of Harman Direct Positive portraits and controlling it is a slippery business indeed. Here's where I'm up to:
I use a 2 stop orange filter for portraiture to overcome the truly vile ( coarse, ugly, contrasty) orthochromatic rendition of skin tones. My effective EI is 1.5.
Preflash is critical. I use 0.8 seconds under a 4x5 enlarger (150 watt lamp) set high with f16 on the 150mm lens. A preflash of 0.7 seconds or 0.9 seconds is different not only from the point of view of contrast control but the EI of the paper changes too! Testing and optimising for your own system is the only way forward. My first 50 sheets were "wasted" in testing.
Preflash reduces the capacity of Harman DP to deliver a decent black. I use warm fresh Dektol 1+2 to get as much density as I can.
Fixing is demanding. Weak fixer will leave a nasty magenta stain in the paper. I use Hypam 1+4 fresh and warm.
Exposure is deadly critical. 1/3 of a stop makes a visible difference. During a portrait session I have an assistant running to the darkroom with exposed sheets and calling out corrections as the shoot progresses.
Harman ostensibly produced this material as a resource for pinhole photographers. With the limited control available in that genre of photography I cannot see how anyone can get predictable results. In the studio with everything under control Harman DP can yield unique camera-original pictures.
Photography, the word itself, invented and defined by its author Sir John.F.W.Herschel, 14 March 1839 at the Royal Society, Somerset House, London. Quote "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..". unquote.
Dear jnanian and Maris,
Thank you both for your detailed replies. You have given me a great starting point. I am grateful to both of you.
Meanwhile, I've got a related question about pre-flashing HDPP, for how long does the pre-flash last?
I tested and found the time to pre-flash, 150C/150M/150Y on my LPL6700, 75mm f/16, 18" up (enough to cover my 11x14"), came to 7 seconds.
I specifically closed the aperture and dimmed the light on purpose to lengthen the time, being 1/2 a second out on 7 seconds isn't much compared to being 1/2 a second out on a 1 second.
So I flashed a scrap, took it straight outside in my pinhole suitcase, gave it ei6 including the yellow filter gave 1 min in full sun, came out pretty well (maybe a 1/2 a stop too dark).
Then I flashed a full 11x14", loaded it in the suitcase, and left it overnight. The next day, pretty much 24 hours after I flashed it, I exposed it, same ei6 gave same 1 min, but gave it an extra half a stop to 1:30. took an hour or two to get home and get myself together to develop it.
Now, the results aren't bad, but it does look a lot more contrasty than the test strip. It's hard to show in a scan (not least because the paper ain't exactly flat, plus they're different subjects, but at least both were full sun), but I certainly see more separation of tones in the test (house) than in the big shot (beach). Neither are particularly blown out, but there's a lot more shadow detail in the bricks and flowers than in the sand/sky.
So did the pre-flash wear off? Is there any way to compensate besides flashing for longer depending on how long it'll be before shooting?
Of course shooting sooner is preferable, but I wanted to test this on purpose because I'll be away from my enlarger for WPPD on sunday and want to flash before I go, maybe on Fri or Sat
ps, I read someone somewhere say something about 'excited electrons', but surely a pre-flash is just taking an image of a light source, so should be affected by the same rules as latent image stability shouldn't it? (and if an image of a light source wears off after 24 hours, would a regular image do the same?)
An awful lot of electrons were terribly inconvenienced in the making of this post.
f/64 and be there.
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