The Online Darkroom reader Scotty Elmslie has been experimenting some more with Adox CMS 20 in Rodinal and HC110 and is very close to nailing the development of this tricky film. I reckon Scotty's final roll, which you can see at the end of the post, is just about on the money thanks to dilute HC110 and very little agitation.
If so, then this would be a great way of developing CMS 20, albeit you're working at ISO 8. However, that wouldn't be too off-putting as I'd imagine a lot of photographers would be using a tripod with this film anyway to maximise its qualities. With the recommended specialist developer, Adotech, you're supposed to get ISO 20 from the film but many photographers believe the film needs an extra stop even so.
In that case, you're talking about just a 2 ISO difference between HC110 and Adotech and it doesn't take much to see that a quarter stop doesn't amount to a hill of beans in this crazy world (sorry, Humphrey). Then there's the not inconsiderable cost saving between the two developers...
So, with that out of the way, here are Scotty's latest findings. (Part One of his testing can be found here and Part Two here. If you haven't already done so, it would be a good idea to read them both so you know how he's arrived at his present position. Scotty's put a lot of work into this.)
Exposed at ISO 10/6/4 developed in Rodinal 1+119 (2 + 238 ml) for the equivalent of 10 minutes at 68F with 15 seconds initial agitation and 5 seconds every 3 minutes after that.
Still weak in the shadows at ISO 6 but the overall contrast is now about right. However, the increase in agitation was not enough to eliminate the bleeding of unexhausted developer into the lighter tones.
I had a nagging feeling that Rodinal is part of the problem with bleeding of unexhausted developer so for this test I switched to HC-110(G) or 1+119 (1+36.5 for the European concentrate).
This roll was exposed at ISO 8/5/3 and developed for the equivalent of 8 minutes at 68F with 30 seconds initial agitation and 10 seconds every 2 minutes after that.
The change in developer and/or agitation eliminated the bleeding problem. However, the contrast and ISO were both too low.
This roll was exposed at ISO 8/6/5 and developed for the equivalent of 12 minutes at 68F with 30 seconds initial agitation and 10 seconds every 3 minutes after that.
This agitation scheme shows that HC-110 is a better choice for semi-stand development since it reduces the bleeding (bromide drag*) issue. However, it seems that anything but minimal agitation can result in uneven development.
This roll was exposed at ISO 10/8/6 and developed for the equivalent of 15 minutes at 68F with 15 seconds initial agitation and 10 seconds at the half-way point.
This method appears to be optimal, almost fully stand development. The bromide drag problem evident with Rodinal did not recur and the uneven development from too much agitation is gone.
The promise of stand development appears to have been fulfilled since the shadows contain detail and texture while the highlights do not appear to be excessively developed.
Conclusions after Rolls 5 through 8
This film has a response to exposure that I have not been able to develop to a normal contrast by conventional means. The practical film speed for CMS 20 is close to ISO 8. But if you are want a high contrast image with marginal shadow detail and virtually undetectable grain, it is a good choice.
There are other options available (like Rollei/AGFA Pan 25) that result in images with grain that is nearly as fine, can be developed conventionally to normal contrast and have a significantly higher ISO.
Stand development is an unconventional method that can offset the excessive inherent contrast of CMS 20. I had problems with bromide drag using Rodinal that I did not experience with HC-110, so the choice of developer is important. Other developers might be as susceptible to bromide drag as Rodinal or as resistant as HC-110 or T-Max developer.
I develop at room temperature – seldom below 70F but as high as 75F in the summer. Temperatures slightly higher than 68F should not have much effect on the viscosity of the developer but they clearly shorten development time.
* Bromide drag is a term commonly applied to the appearance of dark streaks in darker areas of the negative (light streaks in lighter areas of the print) where unexhausted developer appears to slide down the surface of the negative displacing exhausted developer.
The explanation often given is that the bromide in the exhausted developer is heavy enough to move down the surface of the negative making room for fresher developer. Anything that helps to keep the exhausted developer in place (perhaps viscosity or attraction to the film surface) will counteract this problem.