Currently the best approach is to match the sensor response curves to the LED emmission curves. This results in very specific LED selection criteria, to make sure you do not have light coming in that the sensor will miss.
As an aside - the comeback in vinyl is mostly due to mastering [and to hipsters đ ], the vinyl masters tend not to have the âloudnessâ applied that so often afflicts music releases. (google âloudness warsâ for anyone interested.) This results in the vinyl releases often having an artificially wider dynamic range than the âhotterâ CD release of the same album. This results in the vinyl sounding much better, but CD sounds better if taken from the same master, and the (often-digital) master tapes that the vinyl and/or CD is produced from, sounds better than both.
When both the CD and the Vinyl have the same master used, the CDs dynamic range is considerably wider, and closer to the source material than the vinyl record. People claim to be able to hear all sorts of things, but when we did some blind testing a few years back, we artificially put a âcrackle-popâ at the start of the digital recordings, and people waxed quite lyrically about how much warmer and true the vinyl recording sounded, except of course, that it was the CD track. We put the crackle in at the start to see if people perceived it differently if they thought they âknewâ it was on a record. Hearing is so easily manipulated by expectation, (this is fun for instance https://youtu.be/G-lN8vWm3m0?t=21s) and we have never had anyone consistently able to hear a difference between an analogue master and a properly digitised copy of it.
That argument could play out forever, people love their records and I donât want to spend my small amount of time here stirring up that hornetâs nest, so to get back on track, if you choose the R, G, B LEDs correctly (sometimes this will require a mix of two different spectrum RED LEDs) then you will recover everything the film has to offer. Most prints are pretty lo-fi, and you will get more detail scanning them than could ever have been perceived projecting them.
I am lucky enough to have good friends at RMIT that did some spectral analysis for me of various light sources, projected through film test images, and the separate RGB light source conveyed the widest spectral range of any of the light sources tested, that could be captured by commercially available sensors. Unfortunately the âwhiteâ LEDs with high CRI ratings fare poorly. Partially because the CRI measurement system is badly flawed, resulting in poor reproduciton in skin-tones specifically. Hopefully the industry will switch to CQS which gives a much more true measure.