That’s really interesting, especially your second paragraph. Thank you! It explains why I sometimes struggle to achieve satisfactory mid-tone separation when printing these negatives. One can’t have it all ways, of course.
That’s really interesting, especially your second paragraph. Thank you! It explains why I sometimes struggle to achieve satisfactory mid-tone separation when printing these negatives. One can’t have it all ways, of course.I can't point you to any sensitometry besides my own (see attached extract/examples) because I don't know of any, but if it helps at all I'm not the only one who noticed the "straightening" effect - I recall an article Sandy King wrote about his own experiments with two-bath/divided development in which he discussed a similar finding, which led him to opine it might be a useful thing for negatives destined for scanning.
I don't think "restrained highlights" says much on its own. It has to be relative to something such as an overall gradient, emulsion speed, contrast on another part of the curve, etc. I think a better characterization of this type of development is that one can reduce the overall gradient while substantially retaining emulsion speed and without over-flattening of highlights. It's different than what one typically thinks of as "compensation", where there is highlight compression relative to the midtone gradient.
Based on my own testing, contrast is controlled by time/agitation in the first bath as would normally be the case. The alkalinity of the second bath doesn’t seem to affect contrast but it may affect image structure. Fog will also increase with increasing alkalinity of the second bath as the formulas used for the first bath are not typically “optimized” for the composition of the second bath. Agitation or not in the second bath probably won’t make much of a difference in final emulsion speed or contrast but it might (or might not) affect uniformity. Unfortunately there is relatively little in the reputable literature on “best practices” for this type of divided development so ultimately there will probably be some trial and error depending on your goals.
There are many formulas of this type (Adams, Stoeckler, etc.). The Barry Thornton version is only trivially different than D-23 and is probably as good a starting point as any other variation on the theme.
Yes, irrespective of film type, I always do continuous inversions in Bath A. That is because I came to BT2B via Emofin, as I explained upthread somewhere, and it worked for me. In Bath B, I do as little agitation as I dare. That's because I read what Thornton said about adjacency effects!I ordered some BTTB developer, so am going to give it a try. Firstly, I want to expose a step tablet to generate a curve or two..
AA suggested, that with the long straight-line regions of the thin emulsion films that were available at that time, to develop in bath A for just 2-3 minutes with "constant" agitation........I wonder would this be problematic with T-grain films. Three minutes in bath A is less than anyone has mentioned for bath A in this thread and all seem to state using some method of intermitttent agitation in their bath A............maybe that's accurate, but I didn't check 5 pages of posts. BT recommend some form of intermittent agitation as well in the first bath. I wonder has anyone following used continuous agitation in their bath A, either T-grain emulsion or otherwise.
I ordered some BTTB developer, so am going to give it a try. Firstly, I want to expose a step tablet to generate a curve or two..
AA suggested, that with the long straight-line regions of the thin emulsion films that were available at that time, to develop in bath A for just 2-3 minutes with "constant" agitation........I wonder would this be problematic with T-grain films. Three minutes in bath A is less than anyone has mentioned for bath A in this thread and all seem to state using some method of intermitttent agitation in their bath A............maybe that's accurate, but I didn't check 5 pages of posts. BT recommend some form of intermittent agitation as well in the first bath. I wonder has anyone following used continuous agitation in their bath A, either T-grain emulsion or otherwise.
I ordered some BTTB developer, so am going to give it a try. Firstly, I want to expose a step tablet to generate a curve or two..
AA suggested, that with the long straight-line regions of the thin emulsion films that were available at that time, to develop in bath A for just 2-3 minutes with "constant" agitation........I wonder would this be problematic with T-grain films. Three minutes in bath A is less than anyone has mentioned for bath A in this thread and all seem to state using some method of intermitttent agitation in their bath A............maybe that's accurate, but I didn't check 5 pages of posts. BT recommend some form of intermittent agitation as well in the first bath. I wonder has anyone following used continuous agitation in their bath A, either T-grain emulsion or otherwise.
The time and agitation in bath A will determine the final contrast. It is best to think of bath A the way you would think about single bath development - all the same variables since the Barry Thornton bath A is a functional developer (virtually the same as D-23). Therefore the development time in bath A to produce a target gradient will tend to vary depending on the film. I think 2-3 minutes would be a minimum. I didn’t do less than 3 minutes in my tests (which were mostly FP4 but also some TMX and Delta 100) but there’s no reason not to experiment. As with any developer the more agitation you give in bath A for a given development time, the more development (ie contrast) you get. I suggest starting with whatever your standard agitation technique is.
I also suggest at least 3-4 minutes in the second bath regardless of agitation or the composition of the second bath. Simply put, you want to make sure development in the second bath always goes to exhaustion/completion. Development is rapid in the second bath but by you don’t have anything to lose by giving it some extra time.
I ordered some BTTB developer, so am going to give it a try.......
Sorry...............when I said this, I should have stated more clearly that I ordered the metol, sodium sulphite, and sodium metaborate to mix the BTTB. However I still need a scale for measuring the dry chemical weight, but haven't worked out which one I should get.
Sorry...............when I said this, I should have stated more clearly that I ordered the metol, sodium sulphite, and sodium metaborate to mix the BTTB. However I still need a scale for measuring the dry chemical weight, but haven't worked out which one I should get.
Sorry...............when I said this, I should have stated more clearly that I ordered the metol, sodium sulphite, and sodium metaborate to mix the BTTB. However I still need a scale for measuring the dry chemical weight, but haven't worked out which one I should get.
You don't need a scale. I use the teaspoon method and there's a conversion chart in the back of The Darkroom Cookbook.
The only other question that comes to mind is.......would a scale that weighs only up to 200 to 300g basically cover just about any developer that I may want to experiment with beyond BT2B or should I up the capacity of the scale to cover future needs. I've no idea at the moment what other developers that I may want to try.
The only other question that comes to mind is.......would a scale that weighs only up to 200 to 300g basically cover just about any developer that I may want to experiment with beyond BT2B or should I up the capacity of the scale to cover future needs. I've no idea at the moment what other developers that I may want to try.
Occasionally I need to weigh out 200 grams of Sodium thiosulfate, so I measure 100 grams twice: no big deal
About 7 years ago I bought a generic digital scales (American Weigh Scales brand, Digital Pocket Weight Scales, made in China of course lol) on Amazon for $18. It has served me well in the years I have owned it, without any issues whatsoever. I think that the trick (if you can call it that) with these pocket sized digital scales is: NEVER drop them, or you'll eff them up. I've been very careful not to bang or drop mine, so it still works perfectly 7 years later.
It's easy to look at an $18 device and think "that's gotta be junk" and often, you'd be right. But I have relied on this to measure my chemistry and it has been reliable and (apparently) accurate. I measure amounts as small as 0.25 grams of Phenidone and have no difficulty trusting the measurements. I suggest this is a reasonable scales to choose for your purpose.
This for $39 is what I'm leaning toward, seems like a decent scale, but how would I know, lol.
Digital Platform Scale, 300 g x 0.01 g
This compact digital platform scale is perfect for labs, with 0.01g sensitivity, 300g capacity, 10cm weighing surface, LED display & backlight. Order today!www.homesciencetools.com
This for $40 is what I'm leaning toward, seems like a decent scale, but how would I know, lol.
Digital Platform Scale, 300 g x 0.01 g
This compact digital platform scale is perfect for labs, with 0.01g sensitivity, 300g capacity, 10cm weighing surface, LED display & backlight. Order today!www.homesciencetools.com
My last two chemicals arrived today from Photographer's Formulary. Just one question regarding the sodium metaborate, it arrived a bit chunky when I opened it. Is this normal for this chemical? The metol and sodium sulphite anhydrous seemed normal. I have reviewed the SDS sheets for each.
Also, any mixing or preparation tips I should know?
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