The source of film simulations

Dear developers and users of rawtherapee. Can somebody tell me what is the source of film simulations in rawtherapee? How haldclut Portra 400 related to real portra film?

Thank you in advance!

@AlexandrTantsura Welcome to the forum!

The simulations should match pretty closely. We have lots of talented people who make these cluts, some with actual reference material. The sources should be documented in the source code.

I believe @patdavid did a bunch of the film ones.

Portra 400 was likely a combination of multiple other efforts tweaked to something pleasing.

Thank you all for your quick answers, but they do not solve the problem.
I use RT to process RAW, and found that film simulation profiles do not exactly match real films. For example, Portra 400.

Can you post a side-by-side comparison so we can judge the level of discrepancy?

My understanding is that digital emulations will never be able to replicate film perfectly (except possibly for a fixed illuminant), due to differing spectral response.

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Its an approximation, and can only be an approximation. They’ll never match exactly.

I’d be cautious about that claim. Steve Yedlin can get close enough to fool most everyone.

His techniques are considerably more sophisticated than what’s being discussed, though.

Even with the quick and dirty approach, the profile should be recognizably Porta. Pat David’s answer suggests that the Porta emulation is not actually trying to match Porta particularly well, which might explaint the OP’s observation.