Too vigorous agitation can result in loss of film speed and shadow detail. For developers like Thornton's excessive agitation can result in surge marks. When baths are reused they become more prone to foaming. The bubbles formed can cause uneven development. Agitation should always be gentle.
A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.
~Antoine de Saint-Exupery
I think I've got you. You are saying I should be careful of the intensity of agitation in Bath A (Thornton's Two Bath) not that agitation shouldn't be used as a tool, again, in Bath A.
As an aside, it does work in continuous agitation systems, with the provision that you will possibly speed the dilution of Bath A into Bath B and lose some edge/compensation effect. But that is down to the diffusion rates in the emulsion. I have used a Jobo with 5+5 min at 21C with Delta 100 and 400 at one stop below box speed. I think the biggest issue with the Thornton developer is that it may be too flexible!
I feel, therefore I photograph.
I've run across a number of threads where others state they are using Thornton's (or other two bath developers) in a Jobo or BTZS style tubes. I would love the see some curves comparing different agitation methods, including continuous.
Originally Posted by grahamp
In general, excluding the effects of relative buffering, one would expect changes in agitation frequency to have greater effects on contrast/curve shape with dilute, low-sulfite, high pH developers (think compensating developers like FX-2 where the curve can change materially by changing agitation routine). D-23 variants (including Thornton) are quite "robust" (lots of Metol, lots of preservative), meaning there is less of an exhaustion effect between agitation cycles. Granted there are other factors, but generally speaking I would therefore expect contrast to be somewhat less sensitive to changes in agitation frequency in Thornton bath A than with other types of developers. This is what I have found in extensive testing of dilutions and agitation intervals with Perceptol (a D-23 variant). For example, reducing agitation from 1 minute cycles to 3 minute cycles produced less of a change in contrast than I expected. Highlight densities decreased, but so did shadows/speed. It would then follow I'd use development time in bath A as a primary control of contrast, rather than varying agitation frequency.
That's my two cents at least. To me, with a general purpose, non-compensating developer, once you have an agitation scheme that produces consistent, even development, I wouldn't mess with it in an attempt to control contrast. Development time is always the easiest, least risky variable to change in any process.
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Originally Posted by Shawn Dougherty
not really sure what you are getting at here. Thornton's two-bath controls the highlights (i.e. they are never over-blown).
Varying agitation in both Bath A and Bath B may have some effect on mid-tones but the highlights remain controlled.
The image that is currently on my Homepage had a brightness range of more than 10 stops. The bottom right-hand side was metered and placed on Zone III and the film was developed normally in Barry Thornton's Two-Bath developer. The image prints fairly straight with good shadow detail and a trace of tone in the white walls in sunlight. The only dodging required was to slightly lighten the mid-grey area within the wall in shadow at the bottom right of the image.
I would suggest that you pick an agitation regime that you like (despite other posts, I never have any problems with one inversion every 30 seconds) and stick to that and concentrate on finding which development time suits your work.
Thanks for that, Michael. I have found changing the time by one minute makes a noticeable difference and my results have been perfectly even thus far. So, I shall steer future testing in the direction of adjustments in time.
Originally Posted by Michael R 1974
Originally Posted by David Allen
Bath A is basically just a normal D23 type developer. Normal time and temperature changes affect the highlights like any other developer. The short amount of time in A is the primary control over the highlights. In Bath B exhaustion causes the highlights to pretty much stay where they are while the shadows continue to fill in. It's more of an after bath developer. It is not a true Two Bath Developer.
I agree, David. Thank you for all the contributions to this thread!
Originally Posted by David Allen
Well in my observation it doesn't really matter what reel you're using as long as you're agitating at least 30 seconds in the first minute and 10 seconds out of every other minute.
My results consist of no film spots.. sooo take that any way you want
Neither does mine.
Originally Posted by akitak9821
Get it right in the camera, the first time...