Thanks DanielStone for sharing our recent test results.

And thank you Athiril for the suggestion. Current ECN-2 processing may not require ferricyanide bleach (SR-29) but perhaps for it's archival qualities when cross-procceing many labs still use it. I'm sure stabilizer wouldn't hurt. Kodak recommends Ammonium “UL” Bleach (SR-33). (Module 7, PAGE 30) Then again in Module 8 on page 3 ferricyanide bleach (SR-29) appears to be the recommended bleach. Perhaps they are just interchangeable. Hmmm... Either way, it sounds like a good idea to have formaldehyde there to stabilize for cross processing when ferricyanide is not present in the bleach process but "UL" bleach is also recommended by Kodak.

Here is an old test we did comparing over/under exposure capabilities of Portra 400 and 500T:

We have also been doing controls with most of our testing to be sure of the purity of the film and it's behavior in C-41 chemistry vs ECN-2. Here two shots taken on two different rolls that went through premoval:
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The one on the left is standard C-41 process and the one on the right is ECN-2 process. Both exposed at EI 640 and scanned the same. The densitometery is virtually identical, but the c41 has a slight bump in the blacks (better shadow separation)