Adgitation; in general and for compensationg development in particular

[ki6mf]

I have not tested this in any systematic manner and have noticed that when using my compensating developer, D 76 diluted 20% developer 80 % water 15 minutes development time 2 minutes between agitation, that very gentle agitation is all that is needed. With any strong agitation my highlights ,which are already strong, easily blow out!

I suspect for n-3 gentle agitation is what I will be doing! I used to invert my daylight development tank and now will stop doing this for compensating and will test for -2 and -3.

Like I said this is anecdotal!

[Jay DeFehr]

Wally,

Food for thought; how do you know your developer is compensating? Are you assuming because it's dilute, it's compensating? If it is compensating, how much?

Most compensating developers require quite vigorous agitation, though others tolerate low frequency agitation very well. To find the minimum required agitation frequency, begin with stand development; one minute initial agitation, and that's all. If you get perfectly even development, your testing is complete- no agitation necessary! If you get streaks, mottling, or other uneven development, try agitating at the mid point of development, then @ 1/3 and 2/3, then quarterly, etc., until you find the minimum agitation frequency for your film/developer/scene combination. The scene plays an important part. Some scenes, with large, even-toned areas, or black areas on a white field/ white areas on a black field, etc., are more susceptible to streaking and other development defects than scenes with average densities and lots of detail throughout the scene. GSD-10 and Hypercat are both compensating developers, to varying degrees, but GSD-10 tolerates low frequency agitation much better than Hypercat does.

One indication of compensation is a measurable difference in film speed attributable to changes in agitation. i.e., less agitation = higher Effective Film Speed. Hypercat produces full film speed with standard, intermittent agitation, but loses about a stop with continuous agitation. GSD-10 produces full film speed with rotary agitation, but gains 1/2-1 stop with stand development.

I've read many descriptions of compensation that center around highlights, and shouldering there, but I think this is erroneous. In my experience, it's very difficult to produce a pronounced shoulder in a characteristic curve that should be without one. I suggest the effect of compensation is exactly inverse to the effect of staining. Staining produces an increase in contrast proportional to silver density. As silver density increases, so does stain formation, resulting in a divergence of the respective characteristic curves, beginning at the toe, and increasing with density. Compensation works exactly inversely. The densest, most developer-hungry regions exhaust their supply of available developer first, followed by the next densest regions, working from the top of the curve towards the toe. In effect, stain formation cancels out the compensating effect when printing on graded silver papers, or UV processes, but VC papers are a different story. VC papers essentially undo the cancellation of the compensating effect by the stain. Stain acts like a low contrast filter with VC papers, and since stain is proportional, with almost none in the low values, and maximum in the highest values, stained negatives always print with a split grade effect on VC papers. This effect increases contrast in the shadows, and decreases contrast in the highlights, restoring the compensating effect in the highlights, but creating a strange situation in the shadows. Due to the speed increase of compensation, there will be generous shadow detail, but since there's no stain in the shadows, those areas will print with increased contrast, relative to the highlights. These effects play havoc with photographers trying to do zone system calibrations with these materials. Printing on graded papers is more straightforward. The mutual cancellation effects of stain and compensation produce very straight curves, with luminous shadows, glowing mid tones, and delicate highlights unmarred by excessive graininess.

[ki6mf]

Good Point. I only use D 76 as that is what is available at my lab as school. My normal developer is 1/3 developer 2/3 water 14 minutes is my normal time. For me the question is how do you keep highlights from blowing out when there is a large N- development time with this combination of film and chemicals! The School has tested several combinations of developers and concluded when using D 76 this diluted method seems to work when you have a large n- situation.

The gentle agitation method seems to work for me given my chosen film chemical combination. I suspect I should do as you suggested and test pull out the densitometer and check curves in a systematic way!