A lot of slides were used from the 50s to the 90s for instructional purposes in places of work and remained on a screen for several minutes at a time while the instructor explained the purose of waht was on the screen and were used repeatedly for many years.
These were probably not Kodachromes but were E6 processed slides and in my experience they seemed to withstand the experience very well.
So are Kodachromes that much more susceptible to projector light and to the extent that as little as a minute will ruin them? Surely Kodachrome holiday slides and the like were shown time and time again and when Uncle Harry was explaining what the scene was and how much he and Auntie Hilda enjoyed exploring the antiquities etc it is difficult to believe he was switching off the light after say 30 secs or moving to the next slide.
I recall seeing the same slides( probably E6 admittedly) time after time in the late 50s when families got together and some slides were on the screen for several minutes at a time.
Those slides didn't appear useless or even show any signs of deterioration when shown for the second and third times as they often were.
Sorry, Winger. I don't know where on the computer I saw that. As for me, I still wouldn't project them for very long.
I don't hesitate to project mine occasionally, but I'm mindful not to leave the same slide up too long. I've certainly exceeded a minute though with no harm, repeatedly.
It's worth it, absolutely, to see them as they should be seen.
Now that this matter has circulated in my head all day, I'll try not to feel like I made myself a know-it-all-alarmist. But I swear I saw that in an online Kodak publication, within maybe the last 6 weeks. Could be wrong, but it's not my way to remember things that just aren't true. Or to "remember" something I never actually saw. And I vaguely remember being somewhat stunned also that they stated "1 minute".
Kodak is notoriously conservative. Someone may have used a very sensitive instrument and found they could find the first detectable change after one minute in front of a carbon arc lamp or something, and made the recommendation. ;)
Or they could have discovered 1 minute may not be noticeable at that time, but sets in motion a much faster timetable for future fading.
I know wikipedia isn't the best place to get the most accurate info, but...
I couldn't get to the Wilhelm Institute paper that's in the references, though.Quote:
When stored in darkness, Kodachrome's long-term stability under suitable conditions is superior to other types of color film. Images on Kodachrome slides over fifty years old retain accurate color and density. It has been calculated that the yellow dye, the least stable, would suffer a 20% loss of dye in 185 years. This is because developed Kodachrome does not retain unused color couplers. However, Kodachrome's color stability under bright light, for example during projection, is inferior to substantive slide films. Kodachrome's fade time under projection is about one hour, compared to Fujichrome's two and a half hours.
And I was initially more worried about the possibility of the slide catching on fire or melting while being projected - which is probably from somewhere in my quite active imagination anyway.
Yeah, Roger's suggestion a few posts up is likely it. :)
Bethe, it might not be from your imagination. Movie film will quickly melt if it gets stuck in the gate. It takes a lot of heat, but at 24 frames per second, not for long.