|
Time to geek out about emulsion making and characterization data for the emulsion. TL;DR: Science, science, science, then a characteristic curve plot. I've been characterizing my emulsion batches for some time now, primarily to ensure batch-to-batch consistency but also to help troubleshoot issues that may come up from time-to-time. Beginning with batch 20, I started using a more advanced mixing head when making emulsion. I wanted to accomplish two things: 1) minimize the amount of air whipped into the emulsion, which causes foaming and introduces air bubbles which are difficult to remove and increase the risk of defects such as pinholes in the final emulsion. 2) Delicately improve the shadow details to help with scanning and printing to modern multigrade paper. I say delicately because I worked to still retain that late 19th century look for printing with processes from the time period. This results in a longer toe in the characteristic curve which helps scanning and makes the shadows look really nice. You can see this in the data plots for batches 20, 28, 29 in the chart. The trade-off was decreased contrast and (I think) about 1/2 stop loss in speed. However, I don't want to go back to the old method of mixing because the plates are cleaner with less undesirable defects (vs the desirable characteristics of hand-coating the plate). While the contrast is still high compared to film, the highlights don't quite pop like older plates... or at least that's what my impression is. So I did some testing and researching and figured out what needed to be done to increase the contrast in the highlights.. the result is batch 30. I still need to go out and get some photos under real world conditions, but the batch looks promising. I'll save that for the next post. So what you see below is the raw D logH curve for my emulsion for batches 20, 28, 29, and 30. These curves were generated with a uniform tungsten source measured with a calibrated light meter ... not a photographic light meter for metering a scene, but the kind that an optical engineer such as myself would use for scientific testing (read: more precision and readings given in radiometric values). The 4x5 plates are exposed through a calibrated 21-step 4"x5" wedge at a light level and exposure time to cover the linear region of the curve. After development per my recommended method (note the temperature is captured), the plates are allowed to dry and then measured with a calibrated densitometer. Aside from the test batch, gamma is a hair under 0.8. I'm pretty pleased at the consistency of the batches (all things considered, and not counting #30, the test batch), which is something that I've spent a lot of effort to ensure. I think I do need to kick the speed up a bit, just based on taking photos outdoors in the New England winter. I don't think the mixing method changed the speed, but highlighted the speed loss from some other source (if that makes sense). I have a couple of suspects, but I still need to test... in any case, increasing speed isn't difficult. So I'm at a decision point One note: Take the log H axis values with a grain of salt: The specific values were loosely anchored to bright sunlight conditions in early fall New England, and of course this a non-panchromatic, non-orthochromatic emulsion varies significantly with the ambient UV levels, so you can only get in the ballpark (~ASA 2) for practical metering purposes anyhow. What it does show is that this emulsion is much slower than modern films (duh), and is what you would expect if you were to make your own without sensitization. In an upcoming blog, I'll compare to what I get when I add a sensitizer such as sulfur or gold .. an important step for getting to "handheld speeds". :)   Rocks and Tree, scan of a batch 30 dry plate Wow what a year!
Before I reflect on the past 365.25 days, I want to thank everyone in the photography community who has been so supportive and welcoming to me as Pictoriographica started and continues to take off. While dry plates are awesome in and of themselves, it's all the wonderful and fascinating people I've met and talked to, exchanged emails with or had to honor of enjoying their dry plate results that has made this venture so much fun and made every hour of lost sleep worth it. I hope you get as much enjoyment out of this exciting new world of dry plate photography as I have in interacting with all of you. You rock! On 20 December 2017, I posted a classified ad here advertising the sale of some extra 4x5 plates, packaged in spare three-piece sheet film boxes with a fun label to make them look cool. J. Lane Dry Plates were born! I posted the ad and went to sleep, figuring *maybe* someone might buy a box over the next few days. The next morning I discovered the three boxes of plates had sold in about 15 minutes, and I was shocked to find that my inbox and the ad itself was inundated with requests for more 4x5 and other sizes as well. Since my Christmas break had started, I had no reason not to just run with it. I ended up sleeping very little that break. A year later, primarily because I've brought on a couple of awesome high schoolers to help part time (more on them later), it's only been *just this month* that I once again get to enjoy the luxury of 8-hours' sleep. It's been a great ride so far. There have been snags and hiccups along the way (I hate swirlies and thin plates), primarily related to ramping up the quantity of emulsion I've had to make (almost 100 Liters), the number of plates I've coated (about 10,000 plates), and accommodating all the different ways that people other than myself go about processing them. Fortunately, my technical background (almost 20 years as an engineer solving really hard problems) has enabled me to isolate and address the myriad of issues that have cropped up while improving the quality and -- most importantly -- the batch-to-batch consistency of the final product. As most of you know, this is a side business: I have a full-time job as a systems engineer (formerly lens designer.. I'm moving up in the world) and have kids with all the kids activities that go with it. So my "Pictoriographica Work Day" really starts at around 9PM. As demand continued to grow, I simply couldn't keep up. I had no time for anything else. So last month, I brought on board two awesome part time workers to help me keep up with demand. They are both high schoolers, incredibly enthusiastic about film photography, who are hard working and weren't looking forward to flipping burgers as a career starter. Jack cuts and preps glass, while Laura is quickly gaining proficiency in coating plates. Chances are if you've ordered plates this month, the plates you receive were prepped primarily by them (I've been doing QC while they come up to speed and still pack them and ship them out). The great thing about that is it frees up time for me to sleep and also gives me time to get back into doing R&D to develop new and interesting products. Faster speed, you say? Orthochromatic? New *affordable* dry plate holders? Even cooler things that I dare not even mention yet? 2019 should prove just as refreshingly fascinating as 2018 has been in the world of dry plate photography. So the first cool news for 2019 will be a new "experimental emulsion shop". I will be standing up an online store here on the website to make available plates coated with some of the experimental emulsions that are the fruits of my ongoing research and development. These experimental batches typically generate more emulsion than I really need for testing, so rather than dumping it out I'll make it available to you to play with. The listings will provide some basic characterization info and an approximate ASA value to meter... with the caveats about metering ortho or unsensitized plates applying, of course. These will be "one time runs". Once they're gone, that's it. They'll be replaced with the next thing I'm working on. So that should be fun. I'll close this blog with this: As long as there is a demand for dry plates, I will continue to make dry plates. The original J. Lane Dry Plates will always be available, to preserve the look of the dry plate era and ensure it is readily available as an additional tool in the photographer's toolbox of alternative processes. Happy 1st Birthday, Pictoriographica! |
AuthorI'm the guy behind the curtain, Jason Lane, coating plates instead of sleeping. Archives
June 2022
Categories |
RSS Feed