poita said:
Every cinema experience would have been quite different depending on the print, film stock, the size of the screen, number of foot lamberts, the type of screen, its colour, its reflectivity, the amount of ambient light and even where you sat in the cinema etc.
In the 70s in Australia, nearly all projectors were carbon-arc projectors. That is, they work kind of like a welder, two carbon rods are held near earch other and the 'arc' of elecrtricity between them provides the light for the projector. You had to keep slowly winding the carbon rods inwards towards each other as they burned away, and replace them sometimes in between reels. Carbon arc rods have a pretty fixed colour temperature, this is easily catered for.
Actually, regardless of how they are stored, IB prints do fade, all film stock fades no matter what it is. A 30+ year old IB print will look a lot better than other prints, but will still have shifted somewhat, and it depends how it was stored, how many times it was shown, if it was lubricated correctly etc.
There have been times that restorers have had to go to the IB print. For example The Battle of Britain, when they went to the colour separations to make the DVD they found they were in appalling shape and not fit for use. So they found a truly prisitine IB print and Ted Turner used that for the transfer.
I recently stumbled across that actual print of TBoB that was used to make the DVD, it was up for sale for $5000, and is the best quality print I think I have ever seen.
You can get very good results scanning a good IB print, it won't have the dynamic range of the original negative, but if it was printed well then you can get close. These days it is not usually necessary to do multiple scan passes if scanning a print, the dynamic range and SNR of current sensor technology, especially those from Sony is so good that you can get it all in a single pass by using the correct gamma curves, or scanning in high bit depth and using a LUT. As the dynamic range of a print is already compressed, you can usually get it all in one go, unless it is unusually dense, which would only be the case if you shot extremely underexposed.
With a neg the dynamic range is so high that it may in some cases still make sense to do a multiple pass scan.
I've never heard of an IB print fading; I've had trailers from the 50's that look perfect, and there's stuff dating back to the 30's on nitrate that's supposed to look outstanding. IB matrices can widely vary though. I've had 3 or 4 prints of Thunderball over the years, and only 1 had perfect color registration. The others were off. I don't think that was due to fading, but more due to processing.