Trying to get my ducks in a row for processing CMS 20 II in Adotech IV

I've been developing my own B&W roll and sheet films for more than a decade, and also had success with C-41 and E6 films at home, but I'm getting ready to try CMS 20 II in Adotech IV for the first time. I paid a pretty penny to grab 5 rolls of this stuff in 135-36, and a bottle of developer, because I couldn't find it in stock anywhere in the US. B&H said the last time they got any in was May 2022. So I had to ship it from Germany (shout out to Fotoimpex). I really don't want to lose a roll to an avoidable mistake.

I've combed through the documentation and I think my process as outlined below will yield excellent results. But I wanted to sanity check it with the good folks here, and especially have someone look it over who has experience (ideally successful experience...) with this film and developer.

1. Expose at EI 10, as I'm aiming for (N) development/normal contrast range that will look good printed at Grade 2. I have recently verified my meter calibration so I don't have to wonder if that's introducing error.
2. No presoak, just mix 20ml of Adotech IV concentrate into 280ml of distilled water (1+14 for 300ml total soup). 300ml is enough to comfortably submerge the 135 reel in my Nikor steel tank. Carefully get the soup temp to 22C and pour into tank.
3. 30 seconds of gentle but constant inversions. Tap tank to dislodge bubbles at the end.
4. Exactly one half revolution (180 degrees, not 180 and back) of the tank every 1 minute thereafter until total development time of 10m30s is reached. Be extremely gentle and steady with the inversions; documentation makes it seem like this film is highly sensitive to surge marks around sprocket holes.
5. Fresh acid stop bath (Kodak Indicator Stop Bath mixed at normal dilution) for 30 seconds with constant gentle agitation.
6. Using freshly mixed TF-5 at normal dilution, give 45 seconds of total fix time, with constant gentle agitation.
7. 5 minute final rinse in running water.
8. 1 minute of gentle swishing in distilled water + a drop of Photo Flo.
9. Hang to dry.
10. When completely dry, evaluate density on test frames to confirm how close I got to (N) contrast range.

Sound about right? I'm most concerned about step 6. Even with TF-5, which I've been really happy with for Delta 100, FP4+, HP5+, etc. as well as Ilford MG paper in RC and fiber, less than a minute seems insanely short. But Adox is really clear that overfixing will have a noticeable bleaching effect on the negative.

That all seems more or less right, but a couple of things come to mind.

The emulsion absorbs the developer very, very quickly so I forego inversion completely to avoid surge marks around the sprocket holes. Most of the developing takes place early on, so you can just use the twiddle stick, then go on to the 'swish' method. Certainly no more than 45 seconds fix in fresh fix, it seems insane but try a drop of fix on the cut off film leader to convince yourself. Washing is also quick because the emulsion is very thin, so rather than 5 minutes in running water I use the Ilford wash method, and you could probably halve that if the dinner was burning.

Rating the film is as much to do with your own quirks of metering but I find 6 ISO to be the sweet spot for a 'more or less' Zone V reading judging a patch of grass or something similar. I can't say I've ever had a very badly exposed negative whether I've rated it at 3 ISO or 12 ISO, which is why I split the difference. So the film does have some latitude with the Adotech developer which following the agitation technique is clearly acting in a compensating way to exhaust the highlight development before it becomes too contrasty.

I started using CMS20 in around 2014 in medium format (alas the machine is still broken at Adox) and found inconsistent results were rare but came out of nowhere. The few times when I've had inconsistencies with 35mm have been equally baffling, but in my mind I've narrowed it down to agitation. So don't do this unless you have a problem with streaks etc. but I now tend to use the twiddle stick for five seconds back and forth rather than a swish.

I don't shoot & process a lot of CMS20, but I just follow the development procedure as recommended by Adox. I've only used the 135 format, but never had any issues. Oh, I shoot it at EI 12 based on densitometer reading for correct Zone I placement.

Fantastic, thank you both for helpful answers. I'm really excited to see what this film can do firsthand.

I have not shot this film yet but just bought a couple of rolls and was looking around at how people are developing it. On Flickr, Ruediger Hartung has done beautiful work with it in POTA. I realize this is a different developer, but he has posted several times that the anti-halation layer is prone to cause streaking and can be removed by a pre-soak in an alkaline (carbonate) solution for about 1.5 mins, followed by a wash, before developing. If you have trouble with streaking after your first try, that might be worth a shot.

Good luck!

reference:

First roll is in the books, thanks all for your help.

I bracketed the roll at EI 4, 8, and 16, then developed with the instructions for EI 10 (closest to 8 available) in the Adotech IV documentation. Namely, 22 degrees C, 30 seconds of gentle agitation up front, then the remaining 10 minutes giving 1/2 of a rotation to the tank every minute. 30 seconds of Kodak indicator stop bath, 45 seconds of TF-5, 5 minute wash.

Came out looking pretty bulletproof, I could tell straight off it was overdeveloped. When calibrating dev times for a film, I always shoot control frames at Zone I, Zone VI, Zone VII, and Zone VIII so I can see if I'm landing closest to N, N+1, or N+2, as well as evaluating film speed. These control frames showed that the development was higher contrast than N+2 by a bit, and even EI 16 was slower than I needed to be rating the film. But highlight separation is wretchedly bad, it looks like an orthochromatic film with open shadows and blank everything else. Chalk it up to way too much contrast.

I'm going to reduce development significantly for the next roll, probably 10 minutes at 20°C instead of 22°C. That matches their recommendation for EI 6. Probably bracket at 14, 16, 18 (half stops in either direction from 16) as well just to be safe, but I think I'm almost there.

That said, the resolution of this film is pretty astonishing. It's defeating my Nikon LS 4000 scanner at 4000 DPI resolution (i.e., I believe there's more detail on the film than the scanner can capture). I've never bothered to exceed 2000 DPI with that scanner for any other film, including Delta 100, since it seems to just bloat filesize without increasing actual resolution meaningfully.

So I tried my hand at DSLR scanning with my 5D Mk II and an adapted 50mm f/3.5 Macro lens + tube to get to 1:1 magnification. Shot at f/11. It's not any better than the scanner, though whether that's because I've maxed out my sensor or because I'm not good at DSLR scanning, we'll see. Even in the areas that are extremely dense, there's virtually no grain to be found.

I don't usually scan my negatives anyway, so I think I'll try setting Grade 00, and printing the highest magnification I can get out of my Beseler 45MXT + 50mm EL Nikkor lens. Just an 8x10-sized cropped area of the biggest enlargement size I can produce without projecting onto the wall. Maybe I'll scan that and compare it to the negative scans.

Pretty rad film. I'm excited to get some results with more usable contrast.