Microfilms are a little bit delicate to process, because the extremely thin emulsions are very contrasty as they shall be regarding the original purpose. Anyhow, for pictorial use we don't need specialized and very expensive developers as some distributors want to make you believe. Simple Rodinal 1:100 or 1:200 already gives nice results. And Caffenol-C used in an adapted manner produces state-of-the-art results.
Here we talk about the Copex Rapid from Agfa Belgium. I got it in an older package as the so called "gigabitfilm", and yes, the naming imho was a serious aberration of taste and the film was sold together with an expensive and very doubious developer. That initially brought the whole category of microfilms into discredit.But enough wining about people who only want to empty your pockets. This blog is ad-free and will stay so as long as the host will allow it. Caffenol strikes again!
Caffenol-C-L is a weak or compensating developer ideal for extended stand development or for a low contrast development in some minutes. Here I used Caffenol-C-L with no restrainer (no KBr or salt) for 13 minutes/20°C, regular agitation (30 sec initially, 3x every min) and the film was exposed at EI 50. The strong backlight is a challenge for any film/developer combo and of course you need a proper exposure.I metered the foreground, added 3 stops (for the zonies: it was set to zone 2) and still have a good tonal resolution in the sky. The Copex Rapid is told to handle a contrast range of 14 stops, try that with your full format DSLR ;-) Grain is virtually not existent or not resolvable with my humble Canoscan 8800F. The density range of this negative is D = 0.2 - 1.8, so it should be printable perfectly on silver paper.
The very thin emulsions of microfilms only need a very short fixing time, maybe less than 10 seconds, in normal strenght fixer, so you should dilute your fixer much more to get at least a fixing time of 1 minute to not overfix the negs. Make a clearing test!
Best regards - Reinhold