Thanks for that. Would you take into consideration the water used for mixing? I.e. mineral content reflected in ph and oxygen content? I know our water here is really waky and surely will trip any mixture by more than 0.1. Sure, with a home brew I'd measure the grand total after mixing and then correct. But most 'consumer' C-41 kits never make a mention of it, never mind reminding to check/control the ph. Would that be more important in a home brew?
As you mention that one chemical needs 1mg accuracy, I assume you refer to Iodine. The recipe I am looking at does not mention iodine at all only potassium iodide and that is in the blix. Do you mean that? It is used in a fairly small amount of 1.0g so 1mg would be 0.1% variation, not a big one, but alas, maybe relevant. Of course, you might have another recipe in mind actually using iodine. Or maybe the amount given (1g) is wrong anyhow.
It would be great if you could share any more accurate information you might have, or at least point me to it, I could use to possibly use, to get better 'mixtures'. Unfortunately I have not found any information in the last weeks giving weights as, say 1.032g i.e. accurate to 1mg. The best I have seen is weights given to 0.1g implicating an accuracy of 100mg
For that matter, it would be great to know, possibly before delving to deeply into my adventures or to better guide them, would deviations can I realistically expect, if say, the ph is of by 0.5 or even 1? Similarly with the (I assume) potassium iodide, if I am off by 0.1g?
Maybe I am missing the obvious, but something I modify with 5 or 10cc when printing seems trivial to worry about. The (in-)accuracy of the aperture ring markings on the lenses, temperature (!) dependency of my spotmeter (never mind the inbuilt on) as well as their accuracy due to what-not and colour shift's due to daytime, clouds, humidity, etc. probably produce way more variance anyhow.
But as said, it would be really great if you could give me some hints where I could find the information you base your knowledge on so I can do further reading myself. Possibly even a better C-41 recipe if you can spare one
BTW don't get the idea I see self mixing as _the_ way to go. It's one of many ways. I like diversity and exploring.