John,
Virtually anything you can do with a two-bath developer can be achieved with some other method. But the primary advantage of two-bath development is that you get maximum shadow detail without having to worry about blowing out the highlights. With any other method, including very dilute solutions with minimal agitation, it is always possible to develop too long and blow out the highlights. The mechanics of development make this impossible with two-bath development.
The advantages of two-bath development, as I see it, are. This is repeated from my article in VC.
1. No loss of emulsion speed. Long toe films like TRI-X 320 that normally must be rated about a stop slower than box speed can be rated at box speed with two-bath development.
2. Compensation with high contrast scenes.
3. Most films developed in two-bath developers have a very long straight line in the curve, with short toe and shoulder. This spread the compensation over the entire curve, not just the shoulder, as is the case with most compensating type developers.
4. Surface development, which results in higher sharpness.
5. Very economical.
6. Exhaustion of the developer enhances adjacency effects, which increases apparent sharpness.
I would add that with two-bath development there is no need to take notes in the field for future development strategy. One just exposes for the desired shadow values and the mechanics of development controls highlight density.
There is definitely more control with time and temperature development using Zone or BTZS methodology but sometimes this degree of precision is not needed, as for example when one plans to scan the negatives.
Sandy King
Thanks for the reply. I had read this part and noted that this was true of development by inspection. What if D23 were used for M/F in small tanks ? I wondered what kind of result could be expected without Sol. B, or possibly some testing would need to be carried out.
Regards,
John.