Paul's Random questions #1

I have some random questions that probably are not deserving of a full post. If you had answers, please share them

1) I'm working on a poor man's jobo expert tank. I've only seen pictures, pretty much. Does the tank fill totally with chemicals (i.e. no air space anywhere in the tank) or does it only stay in the tubes and top of the tank? I'm guessing the latter (i.e. the areas other than the tubes are sealed and filled with air).

2) RE: BTZS...I'm considering going full in on this as far as getting set up with an enlarger and step wedge to do my own testing. I'm wondering re: roll film, will this help understanding how to "push" film in a controlled way? I.e. if I'm shooting roll film it looks as though using one the curves from one of the longer development times will give me a much better idea of what's going to be on the film than shooting at 1600 and hoping for the best/using the ultimate development chart. I'm not wording this very well, but I'm thinking that if I plotted out the curves for, say, TMY-2 for 1600, I might have a lot more control shooting roll film in low light.

3) For my poor man's jobo thing, when I'm initially putting in the developer, with my current design, it's going to be hard to fill the tank evenly at the begining. There will probably be about 10 seconds where there is some splashing. In general, will a 3 minute presoak generally eliminate problems with splashing?

4) In another version of my poor man's jobo (that's still in my head), I eliminate the filling problem, but I'm unable to invert the tank (this version relies on intermittent agitation). Are there any agitation methods that work that don't involve inversion? Something like a gentle paint spinner?


Sorry they are not the best worded questions but they are the best way I can explain my half thought-out-thoughts. If you have any ideas, I'm all ears.

Thanks
Paul

I'll answer #2: Yes, you should have a much better idea of what is going on for push-processing roll film. At the very least you'd get a more exacting film speed to use. What you won't get however is the per-image contrast control since you can't develop each shot separately.

If you're using Plotter and/or ExpoDev, the other big thing you will get is better control over the reciprocity compensation needed for your film/developer combination. Reciprocity failure is different for each combination and it's good to know what you combination requires. I know of no chart that gives truly accurate (and tested) reciprocity data like Plotter/ExpoDev gives.

Overall though, I would expect that BTZS testing with roll film works out quite a bit better for you than hoping for the best or using a generic development chart.

David

The way that an Expert drum works is that it is vertical when it's being loaded with film, and horizontal during use. It is filled with just enough chemicals to develop the film, and nothing more. The back end of the tank is not sealed, as the tank allows tempered water to flow in and keep the chemicals at the proper temperature. There is a YouTube video of a clear plastic tank in use. That should be educational for you.

Thanks David. That confirms my hunch.

Brian, is this the video you were talking about:
http://www.youtube.com/watch?v=NuFNUO3H6v8

Or is it something else?

That's homemade, but I saw it the other night, my design is sort of like that (and inspired by that). Basically PVC pipe in a Chromega 11x14 drum. My question is if I load the tank approx half full while it's on it's side, the developer is going to hit 1/2 the film early and somewhat inconsistently, before I start it rotating. I'm wondering if that's going to be a problem. I'm planning on a full presoak with the drum verticle first, and then the developer, I'm just hoping that the pre-soak will be enough to mitigate the developer splashing in there. The chemicals load in fairly fast in these drums so I think I'll be alright though.

(I'll look at the video later)
The chemicals are normally poured into the expert drum while it is rotating. What I do is that I put the developer into one tube (marked with tape on the outside), and then load the other tubes with film. Then when I flip the drum horizontal and start rotating it by hand on the idler wheels, the chemicals pour out and coat the film evenly. Sure, I'm down one tube on the drum doing it that way, but that's OK by me. My CPP3 doesn't have the upgraded motor, so I can't use my expert drums on it.

Hi Paul,

The Expert tanks are excellent designs for rotary processing. The cylinders are slightly barrel-shaped to allow solution circulation to both sides of the film, and each cylinder is canted slightly inward at the top, which facilitates filling at the bottom of the rotation, and dumping at the top, and the open bottom allows tempering. The tanks are easy to load/ unload, and require a minimal solution volume. There's really not much to want in an Expert tank.

Intermittent agitation is a separate design question, and requires a much different approach. My designs are very simple -- a single slot tank for each sheet of film, and agitation by displacement. In my prototype, agitation is facilitated by a rubber squeeze bulb like the ones used for pneumatic shutters. Air (though nitrogen could be used instead) displaces the developing solution, which is forced into a reservoir, and then back into the tank. An even simpler design is a hard-sided bladder. To displace the solution, squeeze the sides of the bladder, like a juice box, or simpler still, use head space as the reservoir and invert the tank to agitate. There are a number of potential variations in even these simple designs, and I just haven't had time to work through many of them, except mentally, but my little prototype works like a charm. These daylight processing designs lend themselves well to automation with single sheet resolution.

I'm working with a friend to generate files for 3D Printing a version of these slot tanks for 4x5, but the design is scale-able for any format. Maybe someone with automation chops will adapt the principle to a multi-slot, automated processor. I think a processor of this type the size of a Jobo CPP could process from one to dozens of sheets of film by individual parameters, but maybe it's too late for all that.

Jay,

Those sound good. For a while I think you were keeping mums the word on this stuff...is it out in the open now? Just wondering. My poor man's jobo project may or may not be a failure. There was a lot of cutting of PVC today but I'm not sure it's actually going to work.

I have question #5:
5) If you are testing a development system for evenness of development, what's would you use as a picture that's the hardest thing to develop evenly? My thoughts are a wall of consistent color or a blue sky.

No need to photograph anything, Paul, just flash your film under an enlarger or other even light source. Was I keeping my slot tank under wraps? I wonder why? I probably wanted to test it to see if it worked before I made an ass of myself. I sent some pics to someone who was curious about it, but I don't remember who-- Bob? In any case, I don't have a lot of time to develop the project beyond generating the 3DP files. When that's done, anyone who wants to print one, or modify the design, can do so. Isn't technology fun?!

Jay, I thought you were going to patent it. Maybe I made that up. I'd love to see some pictures. Unfortunately I have neither enlarger nor even light source. Although I'm looking to get one.