man, i totally wish it did. great idea.
no the C330's are the RB67's of the TLR world, chunky, featured, and awesome. no darkslide though. however when i'm next in the darkroom i'll try that out, with a better meter on the reversing exposure that way too.
Paper Negative Reversal Process
It does work on FB, but there was some staining that I couldn't solve. When you look at what the paper is going through it isn't surprising, at least to me. Don't let that stop you from trying, that was just my experience.
Originally Posted by SMBooth
The Process Analyzed
I went to the darkroom this afternoon and put some time into getting a better idea of what's going on with the reversal process, and how to try and optimize the results. For this round of tests I essentially tried to replicate the conditions that have worked in the past for me in my bathroom, and intend to further experiment in a controllable fashion rather than just guessing and checking.
This is what I came up with today. Developer was Ilford Multigrade at 1:3 dilution. Paper was some old Kodak Multigrade RC II. I set up the enlarger without filters, using a 50mm f2.8 projection lens (for speed and the size of the projected circle). The picture above shows all the stuff I exposed, first a test for max black, then the smaller strips on which I tried a nine stop exposure range. The larger strips were a dialed-in five stop exposure range in 1/3 stop increments.
For this test I began quantifying my exposure in lux-seconds to have a universal unit of comparison for the different exposure intensities between the much slower and smaller intensities which create the negative image, and the short intense exposure which induces the tone reversal.
A close-up of my results, and the development information for the big strips. As you can see, the process is sensitive to changes in pre-flash development and flash duration/intensity. My feeling is that a slightly lower developer concentration might provide better overall contrast range compared to the results I achieved today. Also, I'm curious about what, if any, effect a shorter and brighter (but same lux-second) reversing flash would have.
I can post my complete exposure data if anyone is interested, but it will likely be quite different for other paper/developer combinations. My estimations of about 0.2s flashes for the self-portraits I posted earlier in the thread seemed to produce the best results today (I calibrated the enlarger to match the measured brightness of the light at counter-top distance). Maximum black on the test strip, both negative and reversed, was achieved at ~32 ls exposure, minimum reversed density (2 stops less than max negative black) at ~ 10ls, and max reversed density (starting 1.67 stops than min rev density) at 3.2 ls and less. The reversing exposure was 64 ls for the nominal 0.2s exposure at a measured 7 EV, twice the amount of light to produce max black.
Thoughts? Comments? Criticisms?
edit: looking carefully, as I hadn't yet today--I struggled to get these tests finished with a migraine coming on, which I've only now come clear of--test strips 4 and 7 have a reasonably large difference in development and exposure times, producing very comparable and good results. As with my earlier feeling, this procedure does have a fairly wide sweet spot.
Last edited by andy_k; 12-06-2012 at 07:50 AM. Click to view previous post history.
Alright, another go 'round, looking to see the effect of changing developer concentration in conjunction with variations in exposure.
The exposure range for these strips was from 2.5 ls to 12.5 ls (the 10 ls zone still the lightest after reversal) in 1/6th stop increments. Reversing exposure the same, other than where indicated. The first six strips were developed at 1:4 dilution, with the seventh at 1:5.
it appears to me that developer concentration has a similar effect to shifting exposure/development when push or pull processing on film; there is an inherent compromise between tonal range and tonal contrast.
it seems that at these very high developer energies/concentrations that the relatively small variations in exposure have a smaller overall effect, and need to be within a narrower range, than developer concentration.
Any input? I'd love to know what Photo Engineer might say about any of this, or anyone with more technical knowledge than i have.
Hey again gents (and ladies?),
Quick feedback from my experience using powerful flash heads to stimulate the reversal process: it makes a huge difference. Without really having numbers to relate to the above information, or surviving visual (scannable) results to give you, I noticed a massive increase in overal tonal range and contrast using studio strobes to hit the negative image with.
The reason I don't have anything to show you to prove it is a result of my recycling of fairly old fixer in my portable paper-picture kit. Having long since dissolved even the aluminium off of the bottle seal, and smelling strongly of ammonia, the fixer somehow bleached the developed positive images from very nice looking black and white to a creme and rusty brown. No idea what was going on there, but sadly the great reversal results were lost.
Anyone else try out my approach yet? Particularly with a larger format camera?
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I haven't tried it but I've been reading with interest these past weeks and hope you keep relating your experience! Neat idea to try to get this process under control.
It appears that a functional EI of 25 produces really great latent images that are very suitable for reversal, provided that your scene is illuminated with only 2 - 4 stops of luminance range. Reversing with a very powerful strobe is unquestionably the superior method, compared to bright halogen light.
I suggest giving it a try if you're interested, see what happens.
I'm sorry, but I don't see how a more powerful re-exposure can INCREASE the effective ei...then again I never used multigrade kodak for my experiments--I know that it's much faster than the ancient agfa stuff that I used...
all my experience have pointed to more re-exposure and 2nd development giving more density UNLESS you are overexposing in the 2nd exposure to the point that you're gettin solarization/partial reversal or total reversal happening...that may be the case and if it's controllable, then this may be worthwhile....man so busy....but we'll see maybe I'll be able to play around and try it out myself and just see for myself what's possible...first thing I'll do though is start from scratch with the olde kodak polycontrast for the extra speed and see what various re-exposures to GROSS over re-exposure do...I'll do real object pictures though...test strips really give me no useful information on how it reacts to real objects
OK...tried again for the first time in a year...this time I used some kodak polycontrast I had and got a decent speed between EI 12 and 6...like 6ish...they are still drying now. So maybe this will actually be ok to do---they look very good---oh that's the ei fro human flesh to be "white"...which kind of blows out other light colored things--it's closer to ei 12 to 25 for "dark skin" the way properly exposed film looks with a blue filter
to get a "normal" looking white skin portrait, the speed is slower.
ANYWAYS, the reversals look fine--clean whites BUT the paper I have found...is fogged...all my olde paper...it is VERY old too...when I develop it with no exposure it turns grey--so this age-fogging makes it ok for reversals--I determined this AFTER I tossed the paper in the trash and turned onthe lights after testing a bunch of sheets and finding them all fogged...So--it looks like I could have used all that old paper for reversals just fine--the bleach step burns off the fog...oh well...it was like the age-fog pre-flashed it--I did not flash the paper with light.
SO...LEARN from my mistake--DONT TOSS what looks like bad fogged paper---USE IT FOR DIRECT REVERSAL!!!!
I'm going to buy NEW multigrade paper and see what I can get without pre-flashing.
OK here are results of experiments using FRESH, new paper (ilford multigrade RC) AND some PROPER paper developer (ilford PQ universal).
First experiment: deveoped fresh paper in safelight in the same hc-110 from last time AND also in ilford PQ universal
results: the hc-110 developed fog on the new paper == much much more slowly than the old paper, but it was developing it where the PQ universal developer had NO such fog. 2' development with these.
Second experiment: same as the first, but with paper that had NEVER been exposed to safelight and developed in complete darkness
results: same--had fog with the hc-110 and none at all for the ilford PQ.
Therefore, it's not the safelight--it's the developer. SO Lesson #1 is: use paper developer.
SECOND EXPERIMENT--EXPOSURE....shot starting at iso6 (where the last "hot developer fogged" paper looked best) and didn't get "good" results till 4 stops more exposure. All were developed using the ilford PQ as the first developer to avoid all fog.
RESULTS: slightly overexposed at iso 0.8 and a slightly underexposed at iso 1.6...so it appears that ISO=1 is the sweet spot for bright looking skin with this blue/green-sensitive emulsion. This is for NO fogging of any kind, including pre-flash.
Comparing with the last batch, there is more dmax--blacker blacks when no fog is introduced. Fog results in less dmax-this goes for fog introduced by an overpowerful first developer and should also go for pre-exposure/base fog.
Fog INCREASES SPEED and decreases perceived contrast (everybody knows that)...but the decrease in contrast really doesn't seem to be all that much--the biggest gain is in effective speed---HOWEVER--this comes at a price--the fogging decreases dmax...the black borders on the first "fogged" batch are less black compared to the latest batch.
It would seem that you can't cheat--you need a LOT of light if you want it done right, no way around it--no sense in getting less dmax (which gives the APPEARANCE of "tamer" contrast) by introducing fog--it appears to be a false economy--you may have a tamer "looking" contrast, but what is really happening is that you are decreasing your END contrast range in the paper by lowering the dmax---the paper can display less contrast and it does so.
Increasing the speed and "taming" the contrast appears to be a false economy---and it also introduces another "uncertainty" factor in the results--making it more difficult to get a decent process control down--two exposures gives two exposure uncertainties added together--this is likely enought to mess anyone up given the contrast/responsiveness of the paper. The most consistent, repeatable and reliable results will be obtained with NO pre-flash and using FRESH paper and a PAPER DEVELOPER with plently of restrainers in it for a first developer.
So in short: good results white skin portraits for this is iso=1, FRESH ilford multigrade RC, PAPER DEVELOPER--PQ universal first developer. NO PREFLASH.
to get this a hasselblad 80f2.8 wide open lit by 2x travelite 750s on full power was used. The paper was loaded in hasselblad/sheet film holders.
If you have a slower lens and bellows factor for larger format, then it appears that there is no way around it--get more strobe power of use time exposure in sunlight or powerful hotlights.
On the plus side, the paper IS DESIGNED to be exposed by a tungsten light source. so hotlights/time exposures may just be the best for this type of use...that's another experiment...using hotlights and determining ISO with them.
Last edited by johnielvis; 12-25-2012 at 11:41 AM. Click to view previous post history.