“How do I figure out how long to expose and develop for?” This is a question I hear again and again as new collodion practitioners are added to the ranks. Recent discussion with one of my students inspired me to this post. I think here is a simple and straight-forward example of how one can easily and quickly determine the two above factors in pretty much any new situation or with new chemistry (provided that all chemistry is harmonious).
Exposure test strip on a plate is done simply. For some reason or another I actually never have done this test when I started, though I’ve seen it and it made a lot of sense.
Before doing the test and with light on, pull out the dark slide in your holder, but not all the way out - only until it JUST disappears from the opening. Now on the inside side of the slide draw a nice big line that will appear just as you pull it to that point – black fat Sharpie works well for this task, it’s black on black, but you’ll still see it. Then mark 5 more spots between that line and the handle of the slide – giving you 6 sections. With the plate in the holder and holder in camera and lens cap on – pull out the dark slide to that big line and give it the shortest exposure you’re testing for (in case of my test it was 1/2sec). Then close the slide to the first mark and give it same exposure – now you have that strip exposed for 2x the previous one (so in my case 1sec). Close it again to the next dot and give it the combination of two previous exposures (in my case 2sec). Move slide in to next dot and give exposure again equal to sum of all previous exposures (so in my case 4sec). Repeat for next two dots.
Above test is all well and good if you know and keep a certain constant ideal development time for your chemistry. However, what if you’re working with a new developer or collodion formula? Or what if instead of working in a temperature-controlled darkroom you all of a sudden find yourself in the desert of Arizona trying to shoot the most awesome cactus ever, but it’s 100°F out? Well, then the “Anton Dev Test” might come in handy. Simply sensitize a plate and give it no exposure, and keep it on the plate for say half the time you think you should in theory hold it on that cactus plate you’re about to nail. At that point, tip the plate away from you and, with developer all but gone off the plate, with a nice steady stream of water (not too strong – squirting rinse bottle actually works great for this) start rinsing the bottom quarter of the plate – back and forth, back and forth. In 5 or 10 seconds move up and start rinsing the entire bottom half of the plate. Then in another 5-10sec move up to three quarter line, and finally in another 5-10 rinse the whole thing. Fix the plate and take a close look to see if any of the development time strips you created have overdevelopment fog in them. If so, see where it starts and then your maximum possible development time should be a few seconds before that fog starts to appear.
My developer was from the fridge and at 57°F, but in the darkroom it was 82°F, so I knew that in those conditions at about 45sec is when fog will start to show up. Personally, I like exposing in such a manner that I can go to the maximum development time possible. Indeed, as you can see in above Anton Dev Test blank plate, it’s the 50sec strip that starts showing slight fog overall and has some very overdeveloped spots where some inconsistencies in the plate were. By 60sec development all black areas are fogged badly.
After working with collodion for a bit, I now know that the below scene, with Rodenstock Sironar 180mm lens at f32, and with my collodion and developer mixes, would need 4sec exposure and 42sec development.
However, there are certain times when you might want to overexpose and under-develop, or just over or underexpose and go to maximum dev time… So, I moved the tripod in a little in order to have more even tones filling the composition, and below is the combination of Exposure Strip and Anton Dev Test.
As shown in the topmost image, in order to most accurately separate development areas I shielded those parts of the plate I didn’t yet want to wash off by laying a larger piece of glass right onto emulsion and pouring water over that, hence the scratches along those lines.
I use KCN fixer - with severe underdevelopment (which is usually about ½ time or less of maximum development time, so in my case 20 of the possible 45 or so seconds) it actually eats away the few image silver particles that had time to form on the surface. With other types of fixers this may not happen, but you’ll have really weak image with blue highlights. At 30sec image is not bad in overexposed parts on top. With 40sec the image is now acceptable in a wider range of exposures in the middle – it’s really all up to you to decide how you want a particular scene to look in the final plate… With 50sec development there’s probably a touch of fog in the shadows, but there’s not a lot of shadows in that strip, so that little bit of it doesn’t really come out as very visible, however, even in less exposed parts, image is now looking a bit flatter. Actually you can see fog pretty well in the 1/2sec exposure 50sec development section, but it looks like tone of the panel that's laying on the roof - it's not, that panel with that exposure and proper development would be near black.
As you can see – there’s quite a bit of leeway in how long you can expose and develop a plate for depending on your personal final vision for your image. The two tests above, in combination or separately, can be helpful to any beginner though when faced with new unfamiliar lighting, scene, or environment.
P.S. Something that might be of interest to all wet plate, daguerreotype and dry glass plate shooters - just two days ago I received a finished prototype of a new line of plate holders that will soon appear for sale via a separate page on this blog like our Custom Lens Caps and Head Brace. As the prototype is not made of final materials and doesn't have the beautiful finish that it will have once ready to see, I opt out for posting the focal plane test plates below - looking spot on agains the known control!