Focusing adjustment on various stocks (Agfa/Kodak/Fuji)

[supa8]

Hi
I was wondering if any focusing adjustments were required between Agfa (Moviechrome/Agfachrome) and Kodachrome/Ektachrome film stocks.

I know that there is a difference in that way between Super8 and Fuji Single 8, as single8 is a much thinner film, but it is often hard to tell the difference between Agfa and Kodak stocks and people tended to use a mixture of both and splice them onto larger reels.

What do you reckon?

[aj]

This is an imaginary problem. And if it were not it would still be splitting hairs

The image is in the emulsion. This emulsionforms the upper surface of the film. The film is pressed against the gate by a pressure plate. So all mulsions are in the same place. So if you focus on the emulsion of the first it will be on other brands too.

[richard p. t.]

Yes, it shouldn't be an issue at all when splicing camera original reversal films together. Camera original film is so-called 'B-Wind' film. When threaded on a projector, B-wind film is emulsion out. Going through the projector gate, the emulsion will be towards the lens. Yes, polyester is thinner than acetate, but with b-wind film with the emulsion on the lens side of the gate, the image will be in the same spot (as aj rightly said). If you were splicing polyester and acetate prints from camera original together (which are a-wind) then the different thickness is an issue regarding focus. As too (and more so) if you splice a-wind and b-wind film together.
But no, different kinds of b-wind film can be spliced together with no focus problems.
IMHO
richard

[MIKI-814]

Then why do I have to readjust the focus during the same reel and same projection when it changes from Plus-X/Tri-X to a Ektachrome 64?

[slashmaster]

Then why do I have to readjust the focus during the same reel and same projection when it changes from Plus-X/Tri-X to a Ektachrome 64?

I've got this same problem with trix and kodachrome on the same reel. The reason is because one film is slightly convex towards the lens and the other is slightly concave towards the lens. Just like one of those spring wound metal tape measures. You can see this on the film while it's still in the cartridge. The problem seems to me to partially go away when I rewind the film tightly and leave it like that for a while, seems to flatten out both films. Try squeezing the spindle of the take up reel while you rewind so it rewinds tighter.