Keith, the fact that it happens to the best of us always gives me hope! I am glad you resolved your issue with the vintage stock. I havenāt changed a single variable. Everything is controlled and replicated, down to humidity level, etcā¦ You mentioned above that my first lin may have been a flux; I thought it so as well, and I made a second print from the negative; both prints were fairly similar when graphed. But since you mentioned it, this evening Iāve re-measured the 129-step printed from the amended master profile and running the 1st linearization again. Iām going to let it dry for a good 24hrs before printing it.
Meanwhile, I created an ICC profile from the first linearization and printed an image using the ICC profile in the QTR dialog. The print came out very well, it was not an easy image, but it was spot on, other than being perhaps a bit light.
Scott, I doubt it is related to the light source, it is stabilized and Iām using an integrator. It could the curing of the inks, perhaps Iām not waiting long enough although Iām letting it hair dry for at least 12hours. My next test I am waiting for a full 48 hours.
I used the smoothing tool to linearize the QTR profile Iāve built for inkjet hard proof and it linearized perfectly, so Iām confident the problem lies in the darkroom.
Scott - I donāt think that Rafaelās original issue in this thread in related to bulb output, at least not directly. Iāve got a bunch of info on metal halide & mercury vapor bulbs. Iāll start posting it on your thread soon. Most of what Iāve seen posted here on various threads have one thing in common, they all have peak output in the 400-420nm range. My old Olec unit is the same, though it is in storage and I donāt have space to set it up currently. Did you see the Olec bulb chart I posted in another thread?
I think Rafaelās fog problem comes from one of 3 sources:
"stale" ferric oxalate and not using any sort of restrainer
overexposure
insufficient Dmax on the negative
(1) is not likely since he got no fog thru rubylith. (2) is possible and fairly simple to test. (3) may be the most likely, and also easy to check if he has a transmission densitometer.
Rafael, did I ask if you had one of those? Anything over 3.0 should be more than enough for total blockage unless you are also overexposing.
Yes, I agree with Keith the problem might be 2 or 3ā¦ or a slight combination of the two!
I performed several tests of exposure time, but I used Stoufferā¦ I am now gone for the holidays with the family (we have both families at 2000 km either way from Switzerland, not too practical!), but as soon as I come back I will perform these tests. I will also use the new curves 2.0, which I guess will block way more than the ones I used before. Maybe these new curves alone will solve the fogging problem. As Keith said, it is not chemical (it was my initial thought) since rubylith obtains paper white. That being said, I am not starting to add a bit of oxalic acid to the ferric oxalate to reduce the likelihood of having some going to ferrousā¦
I will post the result of the exposure time test strip and tell you whether my problem with the fogging is or not gone with the v2.0.
It is unfortunate, but I do not have a transmissive densitometerā¦ only reflective and the spectrophotometerā¦ Otherwise as Keith says I could have measured the Optical density of my negā¦
I saw Gillesā problem is more related to the linearization, ā¦ I cannot comment yet, since I did not go until there, as my whites were not white totally, I found I was not ready yet to perform the linearization when there was a more basic problem to solve. But I will report back with my results (graphs) once I go over the fogging problem.
I understand also that even if Walker talks about a future release of Metal Halide suited curves, the density of the blackest patch (in the neg) will not be of higher density, so that means the v2.0 curves should be (for my fogging problem at least) as good as these future-curves willā¦ however, maybe for Gilles and those with problems when linearizing (maybe in a few weeks I will enroll that band too!) those future curves will make the Masters more suited to the use of Metal Halide lamps? That is something that only Walker could know at this timeā¦
In any case, it is exciting (even if sometimes a bit frustrating) and it keeps us āsocializingā. Thanks to Walker, Gilles, Keith and Scott for all the contributions on this postā¦
Iām thinking too that this is related to over exposure. My question regarding spectral range goes back to my understanding that Pt/Pd emulsions respond best to 350-400 range of UV. I have learned this in a few workshops but donāt have any references.
Iām at the edge of my understanding of chemistry and physics, but I wonder if a transmission densitometer is the best tool for measuring the density of a negative used with UV light as opposed to light in the visible range.
This is all a hypothesis from a laymen. Keith or Walker, do you have thoughts on this?
Rafael, if this is any help, you can send me by post a negative and I can read them for you on both my standard transmission densitometer and UV densitometer. I live near Basel, so we are almost neighbors. I can also send you the Master profile we tweaked with Keith, to see if you get better results.
Scott, Iāll post my lamp data as soon as I get back to my computer. In regards to your question to Keith and Walker regarding transmission densitometer, I just wanted to give you my two cents. I have been using a UV transmission densitometer to linearize my negatives for the past 10 years, until last year. About a year ago, I did two linearizations sides by sides, one using a standard transition densitometer ans the other using Ć UV densitometer. The results were identical so I retired my UV densitometer, as I find it easier to use the other. Using Lab is totally new for me.
I think I read that Rafael uses a Stouffer - which means he is using it either in combination with OHP Ultra or without the OHP Ultra under it. Either way, he may have only determined the correct amount of exposure for the film base of the Stouffer or the combined UV absorption of the Stouffer film base sandwiched with the OHP Ultra. Neither of those would be the optimum exposure.
I would urge Rafael to put the Stouffer away. Take a strip of unprinted OHP Ultra film and place it half over the emulsion allowing some of the emulsion to remain uncovered so early bronzing can be detected in un-covered conditions. This is important if negs are being trimmed. Otherwise the black brush marks will bronze. Calibration takes care of this in printed film.
Then using something opaque, keep exposing in incremental steps (jotting down the time on paper white near the emulsion for each) to find out at what amount of exposure is actually the optimum for unprinted OHP Ultra? We use measured lux rather than seconds - and lux is going to be more accurate because of bulb start up. But - there are a number of ways to get close to the optimum time - and then perform tests to narrow it further if you must use seconds.
If the optimum exposure has been arrived at by sandwiching Stouffer and OHP Ultra - then the emulsion is being over-exposed. If the Stouffer has the same UV absorption as OHP Ultra (which I doubt) then using the Stouffer on its own without OHP Ultra could be used to determine optimum exposure. Finally, if whatever method was used in Rafaelās previous dig neg system did in fact produce the correct exposure for that system - it is not irrelevant with PiezoDN, and a new base exposure using only OHP Ultra should be established.
anyone available to provide the UV transmission density of clear Stouffer base, clear OHP Ultra base, and a measurement taken through the two combined?
Jon, you are absolutely right, and for the reasons you mentioned, I stopped using a stouffer several years ago. From memory, the UV density of OHP is .13 and stouffer is .08, and when combined/overlapped, it is the equivalent of in between step 2 and 3 of a 21-step stouffer. So i find it completely inaccurate to establish an exposure time
The easiest way to go is as Jon mentioned; use a clear film and make exposure steps. I do 1/3-stop increments, which is the equivalent of .10 density.
The other option is to make your own stouffer on OHP, which is what Iām doing. Iāve created a profile using Piezo inks giving me approx. 3.14 UV density and linearized it not using Lab, but density. The result gives me .15 increments for a 21-step and .10 for a 31-step.
Scott - I just posted a bunch of spectral charts in your other thread. I did not repost the metal halide charts that others have posted recently. The ones we have seen so far are essentially the same as the Olec L900/1250. Maybe Iāll add those so we have them all in the same place.
There are at least 3 major type of metal halide lamps the way Olec distinguishes them.
diazo/photopolymer [attachment file=26291]
photopolymer/diazo [attachment file=26292]
photopolymer [attachment file=26293]
All of the specific lamps that people have reported using so far on this forum are of the first type - diazo/photopolymer.
By comparison, the output of most fluorescent BL lamps looks much more similar to the third type. [attachment file=26294]
As you can see from these illustrations, the output of the various lamps, while all within the range of UV-A, vary considerably from each other. There is also another type of fluorescent lamp that is useful for Pt/Pd and other UV sensitive processes, which are Aquarium bulbs usually designated AQA or AQUA or some variation thereon. These have peak output similar to the Diazo-Photopolymer metal halide lamps. I used these back in the '90s but never with digital negs.
It appears that there is a distinct difference in response of Pt/Pd processes to lamps that have peak output at around 350-360nm versus those that that have peak output around 400-420nm. Since the latter seem to produce darker tones from the same Master negative, I think we can say that there are 2 possible conclusions. First, that Pt/Pd is more sensitive to 400-420nm UV than it is to 350-360nm UV. Or second, that the inks are less efficient at blocking 400-420nm UV than 350-360nm UV.
The challenge is to come up with a way to test this that does not introduce other variables. Most of us only have one exposure light. As I mentioned elsewhere, I do still have my old Olec unit but it is in storage and I donāt have space to set it up at this point.
What Iāve observed is that the later (400-420) also requires slightly less exposure over-all (166 units vs 178 units for the former) for maximum black in our lab (with the same chemistry and humidity etc). Also the later does not bronze nearly as easily with Palladium. That said, I need to go back to the lab and confirm the exact bulb we are using!
A dual-light exposing unit with the ability to dial between the two sources would functionalize the discrepancy in gamma and enable a small amount of contrast and tonal control simply by wavelength without having to change the negative or chemistry (something useful for traditional silver!).
Mr. Pradip is on this list (but I donāt think heās logged in yet). Maybe he can elucidate more. Heās the one who worked out all of this with Mike Ware back in the day.
Keith, I was just reviewing the charts and starting to notice that pattern that you articulate so well.
It is interesting that the NuArc NP80 seem to be multi-range with good coverage between 340-390 and then 410-450. I have fresh lamp that I am going to install in my new-to-me 26-1KS.
The NP80 looks similar to the continuous wave xenon lamp in the Amergraph ULF-28. Check out this graph from Sandy Kingās review of the unit.
<p style="text-align: center;">[quote quote=26289]Piezo[/quote]</p>
<p style="text-align: left;">Art, I'm still working on it, but giving the inks a full 48hrs to cure. I'm doing it on Arches this time to see if it makes a difference.</p>
This is a very interesting theory. A few days ago, a friend brought a LF format negative, which he develops in Pyro and has fine-tuned to print in his darkroom. I believe he uses aquarium lights. His prints have a long and smooth tonal range with lots of detail especially in the highlights. We printed the negative in my darkroom, and it was incredibly contrasty, with lots of detail in the blacks but we had lost the details in the highlights. We measured the UV of his negative and a digital negative, and they had very similar density range.
I therefore think that it is the lamp rather than the inks. What do you think?
Jon raised an interesting point concerning the calculation of the exposure time. Yes, indeed i was using a sandwhich of pictorico ultra AND then the stouffer on top. My friend Tim Parkin explains very well the method i followed on his blog here:
I knew it woukd be a bit off since there is an extra layer of Stouffer to compensate for, but not as much as one third of exposure or moreā¦ so maybe that is where some overexposure is coming from and part of my fogging problem? I will perform the strip test just with the pictorico, also using the integrator to calculate the exposures. It seems most of you use this method instead of the Stouffer?
Concerning the test strip method, do you pick up the first time where the uncovered and covered (by pictorico) patches merge OR the time where the two first uncovered patches merge? I have seen the latter is normally reached before the former, as explained by Peter Mrhar on his book Easy Digital negativesā¦
Cheers!
pd: gilles, thanks for your proposal to send you the neg! I will do when i come home in January! It would be nice to meet at some point, you are not that far in the end. Do you know Ian Leake? A great photographer and platinum printer living in Baselā¦
Hello All. I hope everyone is having a joyous holiday season.
Yesterday after getting a fresh lamp installed, I started calibrating my new-to-me NuArc 26-1KS. This work was completed late last night and I havenāt actually made any measurements but wanted to give some initial impressions. The day before yesterday I printed a my 129-step target using the V2 profiles. Last night I coated three 8āx10ā sheets or HahnemĆ¼hle Platinum Rag using the IJM standard Palladium emulsion including one drop of Photoflo and Na2, and then started looking for my Standard Printing Time. I used a combination of the Stouffer 31 step method, and the approach Jon wrote about earlier. Starting with the Stouffer let me quickly understand if I was it the ballpark and the other method to dial it in.
I settled at 320 units and printed the 129-step target. Upon initial inspection, DMax looked good and no bronzing, BUT not paper white. I went to bed thinking I might have a fogging issue, but looking at prints fully dry, I think I am over exposing. Iāll take a few measurements in a bit and then do more testing tonight.
I suspect these V2 curves provide enough density to not need a special Metal Halide curve, but maybe not.
I am glad you resolved your issue with the vintage stock. I havenāt changed a single variable. Everything is controlled and replicated, down to humidity level, etcā¦ You mentioned above that my first lin may have been a flux; I thought it so as well, and I made a second print from the negative; both prints were fairly similar when graphed. But since you mentioned it, this evening Iāve re-measured the 129-step printed from the amended master profile and running the 1st linearization again. Iām going to let it dry for a good 24hrs before printing it.
